AbstractFibrinogen is an abundant protein synthesized in the liver, present in human blood plasma at concentrations ranging from 1.5-4 g/L in healthy individuals with a normal half-life of 3-5 days. With fibrin, produced by thrombin-mediated cleavage, fibrinogen plays important roles in many physiological processes. Indeed, the formation of a stable blood clot, containing polymerized and cross-linked fibrin, is crucial to prevent blood loss and drive wound healing upon vascular injury. A balance between clotting, notably the conversion of fibrinogen to fibrin, and fibrinolysis, the proteolytic degradation of the fibrin mesh, is essential. Disruption of this equilibrium can cause disease in distinct manners. While some pathological conditions are the consequence of altered levels of fibrinogen, others are related to structural properties of the molecule. The source of fibrinogen expression and the localization of fibrin(ogen) protein also have clinical implications. Low levels of fibrinogen expression have been detected in extra-hepatic tissues, including carcinomas, potentially contributing to disease. Fibrin(ogen) deposits at aberrant sites including the central nervous system or kidney, can also be pathological. In this review, we discuss disorders in which fibrinogen and fibrin are implicated, highlighting mechanisms that may contribute to disease.
Fibrinogen biosynthesis takes place in hepatocytes, starting with expression of three genes, FGA, FGB and FGG, clustered in a 50 kb region of human chromosome 4. The genes encode fibrinogen Aα, Bβ and γ chains, respectively. Both FGA and FGG are transcribed to produce two transcripts. The major transcript encoding Aα is transcribed from five exons, but a minor transcript, resulting from splicing of a sixth exon, encodes the AαE chain which is present in 1-3% of circulating fibrinogen molecules. For FGG, a major γ chain mRNA is transcribed from ten exons while in the minor γ’ chain intron 9 is retained, substituting the four amino acids encoded by exon 10 with 20 γ’ COOH-terminal residues. γ/γ’ and γ’/γ’ represent approximately 8 to 15% of a healthy person’s total fibrinogen.21
The fibrinogen genes are co-regulated both for basal expression and when upregulated upon an inflammation-driven acute phase response.3 The latter leads to a prompt increase in plasma fibrinogen after bleeding or clotting events, or to support wound healing.3 Each fibrinogen gene is thought to be regulated by a proximal promoter and local enhancer elements. These appear to act together with tissue-restricted transcription factors, regulatory chromatin marks and a looped architecture to co-regulate expression of the three-gene cluster.54 CpG DNA methylation of the fibrinogen regulatory regions,6 and microRNA87 can also contribute to cell- and state-specific fibrinogen expression.
Fibrinogen mRNA are translated into nascent polypeptides with signal peptides that are cleaved in the lumen of the endoplasmic reticulum. Here the chains assemble, with the assistance of chaperones, first as Aα-γ or Bβ-γ dimers and then as trimeric molecules, by addition of the missing chain. NH2-terminal disulfide bridges connect two trimers producing hexameric molecules. These transit to the Golgi apparatus, where the final Bβ and g chain N-glycosylation steps take place.9 While properly assembled fibrinogen is secreted as a 340 kDa glycoprotein, misfolded proteins are retained intracellularly and degraded by quality control mechanisms.10
During human development, hemostatic proteins, including fibrinogen, are present in plasma around the time of the termination of hepatic histogenesis and spleen vascularization (~10-11 weeks of gestation), reaching levels at term similar to those in the adult.11 Fetal fibrinogen has qualitative differences, notably delayed fibrin formation, which persist for approximately 1 year after birth. Neonatal clots are less dense than those of an adult and have a different three-dimensional structure.12 However, this does not have a significant impact on coagulation parameters such as bleeding time.
Circulating fibrinogen promotes hemostasis as the soluble fibrin precursor, but also by bridging activated platelets, and enabling a correct disposition of erythrocytes, macrophages and fibroblasts around a wound.13 The development and control of these processes is important to stop bleeding, enhance wound healing and promote tissue regeneration. In addition, fibrin(ogen) is implicated in preventing microbial invasion and proliferation upon trauma,14 enhancing host defenses through the assembly of matrices that entrap invaders and recruit and activate host immune cells.15
The association of fibrin(ogen) with disease results from different mechanisms. These include triggering signaling pathways within given physiological contexts, and alterations in the normal range of fibrinogen levels or in its structure. The latter can contribute to altered fibrin clot properties which can impair thrombin and plasminogen binding. In this review, we focus on the involvement of fibrin(ogen) in the development of a range of human disorders, describing its role in different pathological mechanisms.
Bleeding or hemorrhage is the escape of blood from the closed cardiovascular system due to damaged blood vessels.16 The natural control of bleeding is known as hemostasis.17 Many defects in hemostatic proteins, including fibrinogen, can cause pathological hemorrhage.
Quantitative and qualitative variations in fibrinogen plasma levels can be inherited or acquired. Inherited disorders are divided into type I and II.18 Type I, comprising afibrinogenemia and hypofibrinogenemia, affect the concentration of plasma fibrinogen (<1.5 g/L). Type II, including dysfibrinogenemia and hypodysfibrinogenemia, affect the quality of circulating fibrinogen, the latter also affecting plasma levels.19
Afibrinogenemia, which has an estimated prevalence of one to two cases per 10 people,20 is an inherited disease characterized by the absence of circulating fibrinogen due to homozygous or compound heterozygous mutations in one of the fibrinogen genes. These may affect mRNA production, splicing or stability, protein production or stability, or hexamer assembly, storage, or secretion.21 An initial case of afibrinogenemia in a 9-year old boy was described in 1920,22 but the first causative mutation was identified many years later.2423 Since then, dozens of other causative mutations have been reported for afibrinogenemia. The majority of these are null mutations, i.e., large deletions, frameshift, early-truncating nonsense, or splice-site mutations. Missense mutations are mostly grouped in the conserved COOH-terminal globular domains of the Bβ and γ chains which has given insights into structural determinants of fibrinogen hexamer assembly and secretion.10
Bleeding is the main symptom of afibrinogenemia, often occurring in the neonatal period at the umbilical cord. The natural course of afibrinogenemia is usually characterized by spontaneous and severe bleeding, involving all tissues, such as the skin, the oral cavity, the genitourinary tract, the gastrointestinal tract and the central nervous system (CNS). Intracranial hemorrhage is potentially fatal.25 In addition, bone kysts, prolonged wound healing and spontaneous spleen rupture are typically observed through the life of afibrinogenemic patients.19 Hemarthroses are also frequent but less invalidating than in patients with hemophilia. Women are particularly at risk of bleeding during the child-bearing period. Even in women with no known fibrinogen disorder, in a prospective study aimed at determining hemostatic markers predictive of the severity of postpartum hemorrhage, only fibrinogen concentration was independently associated after multivariate analysis.26 In particular, a fibrinogen concentration lower than 2 g/L was found to have positive predictive value for bleeding events.
Paradoxically, afibrinogenemic patients are at risk of thrombosis, a finding replicated in fibrinogen-deficient mice, since primary hemostasis enables thrombus formation, but clots lacking fibrin are unstable and tend to embolize.27 The reasons for increased thrombotic risk are not entirely understood, but could be related to the absence of thrombin sequestration by the fibrin clot, leading to excessive platelet activation.28
Fibrinogen infusions are efficient to treat acute bleeding and prevent bleeding in the case of surgery. Plasma-derived fibrinogen concentrate is the treatment of choice, providing the safest and most efficient profile among the sources of fibrinogen. Modalities of long-term fibrinogen supplementation (on-demand versus prophylactic), as well as the optimal trough fibrinogen level to target, are still unresolved issues. Some concerns have been raised regarding a potential link between fibrinogen infusion and the occurrence of thrombotic events, although available clinical and biological data are controversial.29
While the role of fibrinogen in hereditary bleeding disorders is well-documented,3130 similar afibrinogenemia phenotypes have been reported in mice and zebrafish models. The Fga knock-out mouse (Fga−/−)32 shows spontaneous bleeding, loss of platelet aggregation and clotting function and reduced survival. Serious injuries, overcome by wildtype mice, were lethal for the Fga−/− animals. Females could not maintain gestation and fatal uterine bleeding was observed. Many of the latter effects were corrected by a transgene for the Aα chain, or the AαE isoform, in Fga−/− mice.33 Fibrinogen-deficient zebrafish have an adult bleeding phenotype with cephalic and ventral hemorrhaging and reduced survival compared with that of control fish.34 In addition, venous thrombosis could not be induced by laser in embryonic zebrafish, clearly demonstrating a hemostatic deficiency.35
Congenital hypofibrinogenemia is much more frequent than afibrinogenemia and is often caused by heterozygous fibrinogen gene mutations. Recently, a systematic analysis of exome/genome data from about 140,000 individuals belonging to the genome Aggregation Database showed that the worldwide prevalence of recessive fibrinogen dis orders varies from 1 in 10 persons in East Asians to 24.5 in 10 persons in non-Finnish Europeans.36 Subjects with moderate or mild hypofibrinogenemia are usually asymptomatic since their fibrinogen levels are sufficient to prevent bleeding and pregnancy failure.37 However, in the presence of another hemostatic abnormality or trauma, they may also bleed and suffer pregnancy loss or postpartum hemorrhage. In some cases, due to mutations in FGG, the mutant fibrinogen forms aggregates in the endoplasmic reticulum of hepatocytes and can cause liver disease.19
Qualitative fibrinogen disorders are commonly associated with heterozygous missense mutations in one of the fibrinogen genes and are more frequent than severe quantitative disorders. Although the exact prevalence is not established, it is estimated to be 1 in 100 to 1,000 individuals (0.1-1.0%).36 Two mutation “hotspots” account for over 70% of the detected dysfibrinogenemia mutations. They are at the Arg35 codon in exon 2 of FGA, encoding a critical residue in the thrombin cleavage site of the Aα chain, and the Arg301 codon in exon 8 of FGG, encoding part of the g chain “hole A” fibrin polymerization site.20 Other causative missense mutations are mainly located in the COOH-terminus of the Aα chain which, unlike the Bβ and g chains, does not contain a large, highly conserved globular domain. Thus, missense mutations in this region do not have a severe impact on hexamer assembly and secretion but can produce a dysfunctional fibrinogen molecule present in the patient’s circulation. Of note, almost all dysfibrinogenemic variants affect fibrin polymerization, which results in a variable tendency for bleeding. An updated list of dysfibrinogenemia variants and related phenotypes is available in a recent review38 and an open-access online database (http://site.geht.org/base-fibrinogene/).
Patients with dysfibrinogenemia are frequently asymptomatic but can suffer from bleeding and/or thromboembolic complications.39 Women are particularly at risk of adverse clinical outcomes, including miscarriages or postpartum thromboses.19 Symptoms are heterogeneous with a poor segregation of the clinical phenotype even among carrier relatives of the same causative mutation. Using integrative hemostatic models, taking into account the molecular anomaly, fibrin clot properties and family history, may improve assessment of a patient’s phenotype.
Acquired fibrinogen diseases are far more common than inherited ones. Acquired hypofibrinogenemia may result from different causes including disseminated intravascular coagulation, in which activation and consumption of coagulation factors depletes their plasma availability. Fibrin degradation products seen in disseminated intravascular coagulation further impair normal fibrinogen function.40 Low fibrinogen levels due to disseminated intravascular coagulation are commonly observed in patients with acute promyelocytic leukemia.41 Patients with liver disease can also have low plasma fibrinogen due to impaired production. Hemodilution, massive hemorrhage or medication affecting liver protein biosynthesis can also contribute to hypofibrinogenemia.42 Acquired dysfibrinogenemia results from a health condition e.g., liver disease affecting post-translational modifications of fibrinogen, notably sialylation. Autoantibodies interfering with the physiological functions of fibrinogen have also been reported.42 As reviewed previously,43 several studies have investigated the use of fibrinogen replacement in acquired coagulopathies. Although it is an important treatment option for acquired coagulopathic bleeding, more studies in different clinical settings are necessary to optimize the dosage. In addition, hyperfibrinolysis contributes to the bleeding manifestations in these acquired coagulopathies, highlighting the importance of a subtle balance between fibrin formation and fibrin degradation.44 Lysine analogues (e.g. tranexamic acid) have proven their efficacy in selected clinical situations, such as major trauma (CRASH-2 trial45) and postpartum hemorrhage (WOMAN trial46).
Thrombosis occurs in the major cardiovascular diseases (CVD): ischemic heart disease, stroke, and venous throm-boembolism.47 Arterial thrombosis is associated with the formation and rupture of an atherosclerotic plaque leading to accumulation of platelets, whereas venous thrombosis is linked to endothelial dysfunction and blood stasis which trigger the aggregation of fibrin and red blood cells.48
The involvement of elevated fibrinogen as a risk factor for CVD remains controversial. Early prospective studies found a clear relationship between plasma fibrinogen and CVD event risk5149 and the most comprehensive analysis to date confirmed this.52 Data from 154,211 subjects with no known history of coronary heart disease or stroke, from 31 prospective studies, revealed associations between fibrinogen level, major ischemic cardiovascular events and nonvascular mortality. The hazard ratio for coronary heart disease and stroke was 1.8 per g/L increase in plasma fibrinogen. Similar conclusions were drawn from a study on the presence and severity of new-onset coronary atherosclerosis in the Han Chinese population.53 In 2,288 subjects referred for coronary angiography, plasma fibrinogen was positively associated with the presence and severity of coronary atherosclerosis, after adjustment for cardiovascular risk factors.
Biases in these evaluations may exist due to unmeasured confounding factors and causality between plasma fibrinogen and CVD events cannot be demonstrated. The elevated fibrinogen levels measured may result from an inflammatory state caused by the underlying pathology, and therefore be a consequence of the illness itself. Nevertheless, further evidence reinforces the hypothesis that the fibrinogen level may directly influence CVD events or progression. Intravenous infusion of human fibrinogen into mice, giving a 1.7-fold increase in plasma fibrinogen, led to resistance to thrombolysis, increased thrombus fibrin content, quicker fibrin formation, greater fibrin network density and increased clot strength and stability.54
The appeal of fibrinogen as a causal factor for CVD comes from its roles in both thrombosis and inflammation.5352 Higher levels of fibrinogen can promote CVD events through different pathways (Figure 1A), which, even if they result from a pre-existing inflammatory condition, may further contribute to a poorer clinical state. Fibrinogen may favor atherogenesis when converted to fibrin and its atherogenic degradation products, or trigger lipid deposition and local inflammation resulting in the formation, destabilization, and rupture of atherosclerotic plaques. Promotion of thrombogenesis is another possible mechanism. Fibrin(ogen) acts as a scaffold for blood clots, enhancing platelet aggregation and fibrin formation, making thrombi more resistant to lysis.55 Furthermore, fibrin(ogen) can interact with red blood cells, mediating erythrocyte sedimentation and blood viscosity, while also permitting red blood cells to attach to thrombi. Besides contributing to thrombus size, structure, and stability, red blood cells can alter fibrin network organization, suppress plasmin generation and reduce clot permeability, possibly delaying fibrinolysis and prolonging clot resolution, which may contribute to CVD.48 Fibrinogen is also a selective matrix metalloproteinase 2 (MMP-2) inhibitor. High plasma fibrinogen levels could lead to MMP-2 insufficiency in humans. As this enzyme is vital for healthy organ development and repair, excessive MMP-2 inhibition could result in arthritic and cardiac disorders similar to those seen in patients with MMP-2 gene deficiency.56
There is, therefore, a potential clinical interest in fibrinogen-lowering drugs for the prevention and/or treatment of CVD. However, some studies have not found a link between high plasma fibrinogen levels and disease. While several single nucleotide polymorphisms have been associated with elevated fibrinogen, the analysis of 24 independent genome-wide significant single nucleotide polymorphisms in 28 European ancestry cohorts, including 91,323 individuals, did not support a causal relationship between plasma fibrinogen and CVD events.57 A more recent Mendelian randomization study using genetic variants to uncover evidence for a causal relationship between fibrinogen as a modifiable risk factor, and CVD events as an outcome, came to similar conclusions.58 After accounting for horizontal pleiotropy, the effect of fibrinogen on CVD is likely to be small and so resolving any causal effect will require further analysis using larger sample sizes.
Structural variability in fibrinogen can be linked to CVD. Increased plasma fibrinogen g’ concentration is associated with the risk of myocardial infarction and other thrombotic states.59 Epidemiological data suggest decreased levels of γ’ may be associated with venous thrombosis, due to the capacity of γ’ to counteract a common risk factor for venous thrombosis i.e. plasma activated protein C resistance.60 However, increased levels of fibrinogen γ’ are associated with arterial thrombosis. This has been attributed to the capacity of the γ’ chain to modulate the fibrin clot architecture toward a more thrombotic fibrin network.61 Whether γ’ is causal in this disease or a consequence of increased inflammation is not clear, and further studies are necessary to evaluate the hemostatic properties of fibrinogen γ’ depending on the disease type. Nevertheless, haplotype data are concordant: a haplotype which shows decreased fibrinogen g’ levels was associated with an increased risk of venous but not arterial thrombosis in different studies.6362 By contrast, a haplotype linked to increased γ’ was associated with arterial thrombosis, although contradictory results have been reported.6564
Fibrinogen variants found in congenital dysfibrinogenemia can contribute to CVD in different ways (Figure 1B). These include elevated levels of free thrombin resulting from impaired binding to fibrinogen, or altered strength, structure and stability of the fibrin clot, prompting embolization or compromised fibrinolysis.38 In particular, patients carrying dysfibrinogenemic mutations which significantly increase thrombosis risk (Online Supplementary Table S1) can have a family history of CVD, and experience thrombotic events at a young age.37 Interestingly, four out of seven mutations result in an amino acid change to cysteine, which may bind to albumin, resulting in structurally abnormal clots.66 Polymorphisms in the fibrinogen genes67 have also been linked to CVD: for example, Aα p.Thr331Ala, which alters factor XIII-mediated cross-linking, results in fibrin clots prone to undergo embolization.68 Post-translational modifications of fibrinogen (e.g., oxidation, phosphorylation, glycosylation and sialyation), might also have a role in CVD by affecting clot architecture, the rate and form of fibrin networks or the interaction with platelets and fibrinolysis.67 In accordance with this, dysfibrinogenemic variants that result in the over-sialylation of fibrinogen, aberrant fibrin polymerization or hypofibrinolysis were identified with relatively high prevalence in patients with chronic thromboembolic pulmonary hypertension.69 Fibrinolytic resistance and high proportions of monosialyted Bβ chains were linked to angiogenesis and growth of fibroblasts and endothelial cells, resulting in chronic inflammation and remodeling of pulmonary cells.70
Other known cardiovascular risk factors, including body mass index, smoking, and diabetes mellitus, can also affect the fibrin network and CVD risk.71
Coagulation factors have been linked with malignancy for over a 100 years and high plasma fibrinogen levels, in particular, have been associated with cancer development and progression. Fibrinogen can be produced by some non-hepatocyte-derived cancer cells and present in the surroundings of tumors, such as in breast cancer.72
A meta-analysis examining the prognostic effect of circulating fibrinogen in solid tumors showed a positive correlation between pretreatment fibrinogen levels and poorer survival (hazard ratio=1.51).73 Conflicting results came from studies on hematologic cancers,7674 but overall patients with elevated baseline plasma fibrinogen levels had a significantly poorer clinical outcome.
Fibrinogen-deficient mice (Fga−/−) were protected against hematogenous pulmonary metastasis, but not tumor growth after intravenous injection of lung carcinoma and melanoma cell lines. Hirudin, a thrombin inhibitor, further reduced the metastatic potential of circulating cancer cells in Fga−/− mice, while plasmin depletion had no effect.77 In a colon cancer model, the thrombin-fibrinogen axis was shown to mediate primary tumor development, as it was diminished in Fga−/− mice.78
The aforementioned associations between fibrinogen and cancer do, however, still require investigation as they do not prove causality. Several hypotheses can be made for the molecular mechanisms implicating fibrinogen in the initiation and development of neoplasms (Figure 2). First, fibrinogen binds growth factors, including vascular endothelial growth factor and fibroblast growth factor.13 Thus, extracellular matrix-residing fibrinogen may serve as a reservoir, controlling growth factor bioavailability and accessibility, and influencing cancer cell proliferation, inhibition of apoptosis, angiogenesis and metastases.72 For example, fibrinogen produced by epithelial cancer cells promotes lung and prostate cancer cell growth through an interaction with fibroblast growth factor 2.79 Second, fibrinogen binds to several cell types. Fibrinogen-mediated cellular bridging may provide traction for cancer cell adhesion, shape changes, motility, and invasive potential.72 An example is fibrin(ogen) binding to endothelial intercellular adhesion molecule-1, facilitating the lodging of circulating tumor cells.80 Finally, the fibrinogen interaction with platelets via β3-integrins facilitates the protection of tumor cells from natural killer-cell cytotoxicity, permitting escape from host immune surveillance.81 Furthermore, interaction with integrin receptor αMβ2 has been suggested to modulate the inflammatory response by inducing leukocyte adhesion to endothelial cells and production of pro-inflammatory cytokines in peripheral blood mononuclear cells.82 Thus, fibrinogen influences an inflammatory tumor microenvironment to favor tumor progression.
These studies suggest that modulating fibrinogen levels in cancer patients may have therapeutic potential. Lowering plasma fibrinogen, either via drug therapy or lifestyle changes, may help to prolong survival in cancer patients. Likewise, other approaches targeting fibrinogen-dependent interactions (e.g., inhibitors of fibrinogen-αMβ2 interactions) may also prove useful in cancer treatment and/or prevention.73
The biological complexity of several neurological diseases involving the CNS, such as Alzheimer disease and multiple sclerosis, is not yet fully understood. However, the need to study CNS cells within their environmental context is clear.
The brain vasculature consists of dynamic metabolic structures that work as a continuum from artery to arteriole to capillary to venule to vein.8483 The blood-brain barrier (BBB) is essential to separate blood from extracellular fluid in the CNS. The BBB is formed by endothelial cells that maintain critical interactions with other cells, together with a basement membrane that affords an anchor for many signaling processes at the vasculature.84 By providing a dynamic physical and metabolic barrier between the CNS and systemic circulation, the BBB ensures constant protection of the neural microenvironment from the influx of potentially harmful substances including plasma proteins, immune cells, pathogens and drugs, while maintaining the efflux of toxins and waste products.8483 Disruption of the BBB is an early event that occurs in many neurological disorders, such as Alzheimer disease, in which, along with microglial activation and neuronal cell death, the neuropathological hallmarks include extracellular deposition of amyloid-β (Aβ) in senile plaques and blood vessel walls, and the intracellular accumulation of neurofibrillary tangles containing phosphorylated tau proteins.85 Brain micro-hemorrhages are frequently observed in patients with Alzheimer disease, and BBB disruption correlates with disease progression.86 In animal models of Alzheimer disease, BBB leakage precedes other neuropathological alterations in the brain,87 suggesting that damage to the barrier is implicated in the initiation and progression of the disease.85 BBB disruption is also one of the earliest representative events in the pathology of multiple sclerosis.88 Indeed, BBB disturbance is linked to the inflammation and white matter injury that define this neuroinflammatory disorder.8583 Fibrinogen may extravasate into the CNS upon such events. Once in the brain, fibrin(ogen) can induce signaling networks via binding sites for multiple receptors and proteins, acting as a mediator of neurodegeneration and an activator of innate immunity.85
Fibrin deposits are found in early multiple sclerosis lesions and areas of demyelination in close association with inflammation and damaged axons.89 In Alzheimer disease, fibrin deposits accumulate within CNS blood vessels in conjunction with cerebral amyloid angiopathy.90 In the perivascular brain parenchyma, fibrin co-localizes with Aβ plaques,91 macrophages,92 areas of pericyte loss93 and dystrophic neurites.94
Fibrin formation exposes the cryptic epitope γ377–395, which binds with high affinity to the αMβ2 integrin on microglia and infiltrating macrophages, activating multiple signal transduction pathways to promote inflammatory responses. This is associated with antigen presentation, release of reactive oxygen species95 and secretion of the leukocyte-recruiting chemokines CCL2, and CXCL10.96 In multiple sclerosis this may lead to T-cell recruitment and local differentiation of myelin antigen-specific T helper 1 cells to promote autoimmunity and demyelination.96 In animal models of Alzheimer disease, fibrin(ogen) was shown to accumulate in areas of dendritic spine elimination, even independently and distal to Aβ peptides that aggregate to form neurotoxic and stable oligomers, with ensuing cognitive impairment.97 The fibrinogen-mediated elimination depends on microglial αMβ2 receptor activation and generation of reactive oxygen species. However, the fibrin-Aβ interaction has an additive effect on poor outcome. Aβ can activate contact pathway coagulation to drive fibrin formation,98 protect fibrin from degradation99 and allow a constant inflammatory signal.
Fibrin(ogen) contributes to neurological disease by inhibiting remyelination after vascular damage.85 Fibrinogen can activate bone morphogenetic protein (BMP) receptor activin A receptor type I and downstream BMP-specific SMAD proteins in oligodendrocyte progenitor cells, independently of BMP ligands.100 This prevents oligodendrocyte progenitor cells from differentiating into myelinating oligodendrocytes and promotes an astrocyte-like cell fate. Fibrin-M1-like activation of microglia101 and macrophages96 can also be toxic to oligodendrocyte progenitor cells and further impair remyelination.85 Another possible mechanism is through fibrin-induced phosphorylation of extracellular signal-regulated kinases and production of nerve growth factor receptor in Schwann cells, maintaining them in a proliferating, non-myelinating state.102
Neurite outgrowth inhibition103 and glial scar formation104 may also be triggered by fibrinogen, leading to cerebrovascular pathologies. Fibrinogen inhibits neurite outgrowth by binding the αVβ3 integrin and trans-activating epidermal growth factor receptor in neurons.103 Inhibition of axonal regeneration occurs indirectly by prompting astrocytosis and stimulating the production of inhibitory proteoglycans that form the glial scar. Fibrinogen can carry a latent transforming growth factor-β that is activated when it encounters primary astrocytes, stimulating the production of neurocan, a strong inhibitor of neurite outgrowth.104
Consistent with these observations, reducing fibrinogen levels with ancrod,105 manipulating the conversion of fibrinogen into insoluble fibrin with hirudin101 and interfering with fibrinolysis by tissue plasminogen activator106 all attenuated injuries and promoted regeneration and functional recovery. Similar results were also obtained after treatment with g377–395 peptide107 or a monoclonal antibody against the same epitope,108 revealing an essential role for fibrin in peripheral nerve damage and repair.
In summary, fibrin(ogen) can induce degenerative changes in the CNS through different mechanisms that initiate or potentiate neurodegenerative processes after vascular disruption (Figure 3A). While many studies have found that fibrin(ogen) promotes neuroinflammation through binding to the αMβ2 integrin on macrophages and microglia, pericyte-deficient mice lack a significant neuroinflammatory response until late in the disease. These mice suffer from early BBB breakdown and accumulation of white matter fibrin(ogen) that is associated with diminished blood flow and hypoxia. However, following white-matter injury, no changes were detected in astrocyte, microglia or macrophage responses or pro- and anti-inflammatory cell profiles and/or numbers of astrocytes and microglia in the resting state. This suggests that fibrin(ogen)-driven neurodegeneration can also be inflammation-independent (Figure 3B).105
Association studies have correlated elevated plasma fibrinogen levels with cognitive decline, independently of inflammatory markers.110109 Proteomic studies detected higher fibrinogen levels on platelets from subjects with secondary progressive multiple sclerosis.111 This highlights dysfunctional coagulation as a common thread among diverse neurovascular abnormalities. Fibrin(ogen) may, however, be beneficial in acute CNS injuries by delaying regeneration until the extracellular environment is conducive to repair.100
Pharmacological agents targeting fibrinogen or fibrinogen interactions with CNS cells or other players may have potential as therapeutics for neurological diseases. Such drugs could include agents that enhance fibrin(ogen) degradation, protect the BBB to limit fibrin(ogen) entry into the CNS, or selectively inhibit the interactions of fibrinogen and fibrin with their CNS receptors, αMβ2 or Aβ, while preserving the beneficial functions of fibrinogen.85
Microbial infections and allergic reactions
Fibrin(ogen) is implicated in defense against pathogen invasion,112 for example in peritonitis. Recent findings from experiments in vitro and in vivo show that at the air-liquid interface formed following a skin wound fibrin can accumulate perpendicularly to generate a protective biofilm.14 These structures, which are an end product of clotting and fibrin formation, prevent blood cell loss from the wound but also block the entry and early proliferation of bacteria at the injury site. However, in other settings fibrin(ogen) enhances bacterial virulence15 or contributes to the development and perpetuation of allergic reactions.113
Certain bacteria express virulence factors that appropriate fibrin(ogen) to facilitate their entry into the host, limiting the antimicrobial role of fibrinogen and protecting the organisms from pharmacological treatments. Virulence factors can also enhance bacterial proliferation and dissemination.112
The anti- or pro-invasion effects of fibrin(ogen) reflect the activity of bacterial virulence factors (Table 1) which have adapted to unique host microenvironments. For example, different murine models of Staphylococcus aureus endocarditis require distinct factors for valve colonization. Microbial adhesion and colonization in mice with mechanically damaged valves involve fibrin(ogen), whereas in a model of cardiac valve inflammation, fibrin(ogen) depletion with ancrod did not impair bacterial colonization. Bacterial volume increased in ancrod-treated mice compared to that in controls.114 Further comprehension of the roles of coagulation factors on bacterial virulence may lead to therapeutic strategies for the treatment of infectious diseases, particularly given the increasing demand to find a solution to antibiotic resistance.115
In fungal infections, proteases contribute to inflammation through interactions with the kinin system as well as the coagulation and fibrinolytic cascades.116 In this context, the fibrin(ogen) interaction with αMβ2 is implicated, as it may further react with toll-like receptor 4 (TLR4) in immune cells, resulting in a highly efficient signaling complex that regulates the development of antifungal reactions, but also allergic airway disease.113 Fungal proteinases cleave fibrinogen into cleavage products (FCP) which, together with αMβ2 and TLR4, were found to be essential for fungal elimination by T and B lymphocytes, dendritic cells and macrophages. The fibrinogen hexamer can also inhibit fungal growth, perhaps due to low affinity fibrinogen-target receptor interactions. However, the putative αMβ2/TLR4/FCP complex also triggered innate fungistatic immunity, modest allergic airway hyper-responsiveness and neutrophilia.113 Interestingly, this αMβ2/TLR4/FCP association has been described in unrelated settings, including endotoxemia and malaria.118117 Thus, FCP that play a role in infection-mediated inflammatory responses have a pivotal role in the clinical outcome of patients with fungi-induced autoimmunity.113
Finally, fibrin(ogen) also seems to be implicated in bacteria-driven hypersensitivity reactions. Pharmacological or genetic depletion of fibrinogen in mice improved the animals’ survival when they were challenged with high concentrations of lipopolysaccharide, and impeded the development of a variety of inflammatory conditions.15 In humans, afibrinogenemic patients have reduced responses in a delayed-type hypersensitivity reaction induced by exposure to bacterial antigens.119
Obesity and diabetes
Nutrient excess leads to imbalances in cellular and molecular mediators of immunity and inflammation.120 These may drive metabolic dysfunction while triggering a hypercoagulable state, with elevated circulating levels of fibrinogen being among key coagulation components.121 Initial risk, severe morbidity and mortality outcomes for vessel-occlusive disorders correlate positively with the degree of obesity.122121 Thus, obesity represents a major risk factor for other pathologies, including thromboembolic events, CVD, diabetes, cancer and fatty liver disease.121120
Fibrinogen may be involved in the pathology of obesity. Levels of fibrinogen are higher in obese patients with type 2 diabetes than in obese subjects without type 2 diabetes.123 In addition, plasma fibrinogen levels correlate with fasting insulin levels and disease state advancement in noninsulin-dependent diabetics,124 and while insulin infusion decreases fibrinogen biosynthesis in normal subjects,125 insulin resistance/deficiency may contribute to hyperfibrinogenemia.126 Furthermore, fibrinogen from diabetic patients generates denser, fibrinolysis-resistant clots, while insulin treatment leads to changes in fibrinogen and a more permeable clot.127 These alterations have been attributed to the glycation of fibrinogen and its effect on fibrin clots, potentially contributing to the risk of thrombosis.
Mice fed with a high-fat diet developed fibrin(ogen) deposits in white adipose tissue and liver which co-localized with macrophage accumulation.128 In contrast to Fibg mice and mice without factor XIIIA, Fibg390–396A animals were protected from increased body weight with a high-fat diet, specifically at the fat mass level. These animals, with fibrin(ogen)-γ residues 390 to 396 replaced with alanine and therefore lacking an αMβ2-binding motif on fibrin(ogen),129 showed less systemic and local inflammation, demonstrated by lower levels of pro-inflammatory molecules, adipose tissue macrophages and smaller white adipose tissue adipocytes128 when compared to those of wild-type animals. In addition, the fibrinogen γ390–396A variant led to lower liver weight, steatosis, serum alanine aminotransferase and hepatic inflammatory markers, and conferred some degree of protection against the development of induced fatty liver disease. Glucose clearance and insulin sensitivity were improved, revealing improved glucose metabolism.
Thus fibrin(ogen)-driven inflammation, via leukocyte interactions in adipose tissue and liver, worsens obesity and increases its downstream harmful effects. Targeting thrombin or fibrin(ogen) may improve the morbidity of obesity-linked pathologies.
Amyloidosis is a group of disorders originating from mutations that cause conformational changes, typically involving β-sheet structures, in soluble proteins. These then aggregate as extracellular amyloid fibril deposits in various organs. In systemic forms, amyloidosis can progressively induce organ dysfunction, and be fatal.130
Fibrinogen-driven renal hereditary amyloidosis is a rare group of disorders with autosomal-dominant inheritance caused by heterozygosity for mutations in the αC-domain, which result in improper folding and amyloid formation followed by accumulation and deposition in the kidneys.66 Other elements present in the deposits can further contribute to fibrin(ogen) amyloid formation, namely amyloidosis-enhancing factor131 and serum amyloid A.132 The latter binds to purified fibrinogen and induces amyloid formation and spontaneous dense, matted fibrin(ogen) deposits, independently of thrombin. However, its involvement in renal amyloidosis has not yet been demonstrated.
Fibrinogen-derived amyloid deposits disrupt kidney structure and impair kidney function, effects that become more severe over time, with accumulation of the amyloid. Amyloidosis is associated with hypertension, nephrotic syndrome, and renal failure.66 Several renal amyloidogenic mutations in fibrinogen have been described (Online Supplementary Table S2). Patients with these mutations do not have a bleeding disorder and, when measured, the clotting times of patients with these variants are normal, except those with p.Thr544LeufsTer24 who had a prolonged thrombin time and low fibrinogen level.133
While the kidney is the predominant organ for fibrinogen-amyloid deposition, the pathology of hereditary fibrinogen amyloidosis is not restricted to involvement of this organ. Fibrinogen amyloidosis patients show a high incidence of cardiovascular atheromatous disease with a family history of coronary/vascular disease.134 Fibrinogen deposits are found in vascular walls and atheromatous plaques, associating fibrinogen variant amyloidosis and atherosclerosis. While nephrotic syndrome with hyperlipidemia and hypertension may facilitate atheroma formation, the cardiovascular findings are unlikely to be caused by renal failure alone. Thus, hereditary fibrinogen amyloidosis is a complex systemic amyloid disease that is associated with cardiac amyloid deposition, angiopathy and atheromatosis135134 (Figure 4).
There are currently no treatments available to resolve amyloid deposits. Disease management consists of interrupting amyloidogenic protein supply with supportive care to failing organs, and transplantation. Hepatorenal transplantation appears to prevent disease progression and allows reversal of some organ dysfunction.135134
As the thrombin substrate for generating fibrin, fibrinogen has a critical role in controlling bleeding upon vascular injury, as well as being a major determinant in wound healing, tissue regeneration and mediation of inflammatory responses that help the immune system fight invading pathogens. However, several layers of evidence point to fibrin(ogen) as a contributor in pathological settings (Figure 5). These contributions may result from altered plasma concentration, modified structural properties, or from the impact of polymorphisms on clot permeability, stiffness and resistance to lysis. The presence of fibrin(ogen) in particular locations is a determinant in the development of disease. Here we have discussed human disorders in which the role of fibrin(ogen) is supported by clinical data and animal models. Fibrin(ogen) is also a likely protagonist in fibrotic and arthritic diseases. Continued research will allow a better understanding of these complex disease settings and the impact of fibrin(ogen). Whether the presence, quality or abundance of fibrin(ogen) has a causal role, or is a consequence of the underlying pathology, should be a focal point. Such research will help to evaluate the usefulness of targeting fibrin(ogen) in a variety of human disease settings.
- Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/2/284
- Received September 19, 2019.
- Accepted November 21, 2019.
- Mosesson MW, Siebenlist KR, Meh DA. The structure and biological features of fibrinogen and fibrin. Ann N Y Acad Sci. 2001; 936:11-30. PubMedhttps://doi.org/10.1111/j.1749-6632.2001.tb03491.xGoogle Scholar
- Standeven KF, Ariens RA, Grant PJ. The molecular physiology and pathology of fibrin structure/function. Blood Rev. 2005; 19(5):275-288. PubMedhttps://doi.org/10.1016/j.blre.2005.01.003Google Scholar
- Fish RJ, Neerman-Arbez M. Fibrinogen gene regulation. Thromb Haemost. 2012; 108(3):419-426. PubMedhttps://doi.org/10.1160/TH12-04-0273Google Scholar
- Espitia Jaimes C, Fish RJ, Neerman-Arbez M. Local chromatin interactions contribute to expression of the fibrinogen gene cluster. J Thromb Haemost. 2018; 16(10):2070-2082. Google Scholar
- Fort A, Fish RJ, Attanasio C. A liver enhancer in the fibrinogen gene cluster. Blood. 2011; 117(1):276-282. PubMedhttps://doi.org/10.1182/blood-2010-07-295410Google Scholar
- Vorjohann S, Pitetti J-L, Nef S. DNA methylation profiling of the fibrinogen gene landscape in human cells and during mouse and zebrafish development. PLoS One. 2013; 8(8):e73089. Google Scholar
- Fort A, Borel C, Migliavacca E. Regulation of fibrinogen production by microRNAs. Blood. 2010; 116(14):2608-2615. PubMedhttps://doi.org/10.1182/blood-2010-02-268011Google Scholar
- Lukowski SW, Fish RJ, Martin-Levilain J. Integrated analysis of mRNA and miRNA expression in response to interleukin-6 in hepatocytes. Genomics. 2015; 106(2):107-115. PubMedhttps://doi.org/10.1016/j.ygeno.2015.05.001Google Scholar
- Redman CM, Xia H. Fibrinogen biosynthe-sis. Ann N Y Acad Sci. 2001; 936(1):480-495. PubMedGoogle Scholar
- Vu D, Di Sanza C, Caille D. Quality control of fibrinogen secretion in the molecular pathogenesis of congenital afibrinogenemia. Hum Mol Genet. 2005; 14(21):3271-3280. PubMedhttps://doi.org/10.1093/hmg/ddi360Google Scholar
- Bleyer WA, Hakami N, Shepard TH. The development of hemostasis in the human fetus and newborn infant. J Pediatr. 1971; 79(5):838-853. PubMedhttps://doi.org/10.1016/S0022-3476(71)80405-5Google Scholar
- Brown AC, Hannan RT, Timmins LH. Fibrin network changes in neonates after cardiopulmonary bypass. Anesthesiology. 2016; 124(5):1021-1031. Google Scholar
- Weisel JW, Litvinov RI. Fibrin formation, structure and properties. Subcell Biochem. 2017; 82:405-456. PubMedhttps://doi.org/10.1007/978-3-319-49674-0_13Google Scholar
- Macrae FL, Duval C, Papareddy P. A fibrin biofilm covers blood clots and protects from microbial invasion. J Clin Invest. 2018; 128(8):3356-3368. Google Scholar
- Ko Y-P, Flick MJ. Fibrinogen Is at the interface of host defense and pathogen virulence in staphylococcus aureus infection. Semin Thromb Hemost. 2016; 42(4):408-421. Google Scholar
- Furie B, Furie BC. Mechanisms of thrombus formation. N Engl J Med. 2008; 359(9):938-949. PubMedhttps://doi.org/10.1056/NEJMra0801082Google Scholar
- Smith SA, Travers RJ, Morrissey JH. How it all starts: initiation of the clotting cascade. Crit Rev Biochem Mol Biol. 2015; 50(4):326-336. PubMedhttps://doi.org/10.3109/10409238.2015.1050550Google Scholar
- Williams Hematology. McGraw-Hill Education: New York, NY; 2015. Google Scholar
- de Moerloose P, Casini A, Neerman-Arbez M. Congenital fibrinogen disorders: an update. Semin Thromb Hemost. 2013; 39(6):585-595. PubMedhttps://doi.org/10.1055/s-0033-1349222Google Scholar
- Casini A, Blondon M, Tintillier V. Mutational epidemiology of congenital fibrinogen disorders. Thromb Haemost. 2018; 118(11):1867-1874. Google Scholar
- Vu D, Neerman-Arbez M. Molecular mechanisms accounting for fibrinogen deficiency: from large deletions to intracellular retention of misfolded proteins. J Thromb Haemost. 2007; 5(Suppl 1):125-131. PubMedhttps://doi.org/10.1111/j.1538-7836.2007.02465.xGoogle Scholar
- Rabe F, Salomon E. Ueber-faserstoffmangel im Blute bei einem Falle von Hämophilie. Ann Intern Med. 1920; 95:2-14. Google Scholar
- Neerman-Arbez M, Antonarakis SE, Honsberger A. The 11 kb FGA deletion responsible for congenital afibrinogenaemia is mediated by a short direct repeat in the fibrinogen gene cluster. Eur J Hum Genet. 1999; 7(8):897-902. PubMedhttps://doi.org/10.1038/sj.ejhg.5200395Google Scholar
- Neerman-Arbez M, Honsberger A, Antonarakis SE. Deletion of the fibrinogen [correction of fibrogen] alpha-chain gene (FGA) causes congenital afibrogenemia. J Clin Invest. 1999; 103(2):215-218. PubMedGoogle Scholar
- LakKeihaniElahi Bleeding and thrombosis in 55 patients with inherited afibrinogenaemia. Br J Haematol. 1999; 107(1):204-206. PubMedhttps://doi.org/10.1046/j.1365-2141.1999.01681.xGoogle Scholar
- Charbit B, Mandelbrot L, Samain E. The decrease of fibrinogen is an early predictor of the severity of postpartum hemorrhage. J Thromb Haemost. 2007; 5(2):266-273. PubMedhttps://doi.org/10.1111/j.1538-7836.2007.02297.xGoogle Scholar
- Ni H, Denis CV, Subbarao S. Persistence of platelet thrombus formation in arterioles of mice lacking both von Willebrand factor and fibrinogen. J Clin Invest. 2000; 106(3):385-392. PubMedhttps://doi.org/10.1172/JCI9896Google Scholar
- Mosesson MW. Antithrombin I. Inhibition of thrombin generation in plasma by fibrin formation. Thromb Haemost. 2003; 89(1):9-12. PubMedGoogle Scholar
- Korte W, Poon M-C, Iorio A. Thrombosis in inherited fibrinogen disorders. Transfus Med Hemother. 2017; 44(2):70-76. Google Scholar
- Litvinov RI, Weisel JW. What is the biological and clinical relevance of fibrin?. Semin Thromb Hemost. 2016; 42(4):333-343. PubMedhttps://doi.org/10.1055/s-0036-1571342Google Scholar
- Menegatti M, Peyvandi F. Treatment of rare factor deficiencies other than hemophilia. Blood. 2019; 133(5):415-424. PubMedhttps://doi.org/10.1182/blood-2018-06-820738Google Scholar
- Suh TT, Holmback K, Jensen NJ. Resolution of spontaneous bleeding events but failure of pregnancy in fibrinogen-deficient mice. Genes Dev. 1995; 9(16):2020-2033. PubMedhttps://doi.org/10.1101/gad.9.16.2020Google Scholar
- Degen JL, Drew AF, Palumbo JS. Genetic manipulation of fibrinogen and fibrinolysis in mice. Ann N Y Acad Sci. 2001; 936:276-290. PubMedGoogle Scholar
- Fish RJ, Di Sanza C, Neerman-Arbez M. Targeted mutation of zebrafish fga models human congenital afibrinogenemia. Blood. 2014; 123(14):2278-2281. PubMedhttps://doi.org/10.1182/blood-2013-12-547182Google Scholar
- Hu Z, Lavik KI, Liu Y. Loss of fibrinogen in zebrafish results in an asymptomatic embryonic hemostatic defect and synthetic lethality with thrombocytopenia. J Thromb Haemost. 2019; 17(4):607-617. Google Scholar
- Paraboschi EM, Duga S, Asselta R. Fibrinogen as a pleiotropic protein causing human diseases: the mutational burden of Aα, Bβ, and g chains. Int J Mol Sci. 2017; 18(12):2711. Google Scholar
- Casini A, Undas A, Palla R. Diagnosis and classification of congenital fibrinogen disorders: communication from the SSC of the ISTH. J Thromb Haemost. 2018; 16(9):1887-1890. Google Scholar
- Casini A, Neerman-Arbez M, Ariens RA. Dysfibrinogenemia: from molecular anomalies to clinical manifestations and management. J Thromb Haemost. 2015; 13(6):909-919. PubMedhttps://doi.org/10.1111/jth.12916Google Scholar
- Casini A, Blondon M, Lebreton A. Natural history of patients with congenital dysfibrinogenemia. Blood. 2015; 125(3):553-561. PubMedhttps://doi.org/10.1182/blood-2014-06-582866Google Scholar
- Iba T, Levy JH, Warkentin TE. Diagnosis and management of sepsis-induced coagulopathy and disseminated intravascular coagulation. J Thromb Haemost. 2019; 17(11):1989-1994. Google Scholar
- Chang H, Kuo MC, Shih LY. Clinical bleeding events and laboratory coagulation profiles in acute promyelocytic leukemia. Eur J Haematol. 2012; 88(4):321-328. PubMedGoogle Scholar
- Besser MW, MacDonald SG. Acquired hypofibrinogenemia: current perspectives. J Blood Med. 2016; 7:217-225. Google Scholar
- Levy JH, Goodnough LT. How I use fibrinogen replacement therapy in acquired bleeding. Blood. 2015; 125(9):1387-1393. PubMedhttps://doi.org/10.1182/blood-2014-08-552000Google Scholar
- Kolev K, Longstaff C. Bleeding related to disturbed fibrinolysis. Br J Haematol. 2016; 175(1):12-23. Google Scholar
- Shakur H, Roberts I. Effects of tranexamic acid on death, vascular occlusive events, and blood transfusion in trauma patients with significant haemorrhage (CRASH-2): a randomised, placebo-controlled trial. Lancet. 2010; 376(9734):23-32. PubMedhttps://doi.org/10.1016/S0140-6736(10)60835-5Google Scholar
- Effect of early tranexamic acid administration on mortality, hysterectomy, and other morbidities in women with post-partum haemorrhage (WOMAN): an international, randomised, double-blind, placebo-controlled trial. Lancet. 2017; 389(10084):2105-2116. Google Scholar
- Raskob GE, Angchaisuksiri P, Blanco AN. Thrombosis: a major contributor to global disease burden. Arterioscler Thromb Vasc Biol. 2014; 34(11):2363-2371. PubMedhttps://doi.org/10.1161/ATVBAHA.114.304488Google Scholar
- Byrnes JR, Wolberg AS. Red blood cells in thrombosis. Blood. 2017; 130(16):1795-1799. PubMedhttps://doi.org/10.1182/blood-2017-03-745349Google Scholar
- Kannel WB, Wolf PA, Castelli WP. Fibrinogen and risk of cardiovascular disease: the Framingham Study. JAMA. 1987; 258(9):1183-1186. PubMedhttps://doi.org/10.1001/jama.1987.03400090067035Google Scholar
- Meade TW, Chakrabarti R, Haines AP. Hæmostatic function and cardiovascular death: early results of a prospective study. Lancet. 1980; 315(8177):1050-1054. Google Scholar
- Wilhelmsen L, Svärdsudd K, Korsan-Bengtsen K. Fibrinogen as a risk factor for stroke and myocardial infarction. N Engl J Med. 1984; 311(8):501-505. PubMedhttps://doi.org/10.1056/NEJM198408233110804Google Scholar
- Danesh J, Lewington S, Thompson SG. Plasma fibrinogen level and the risk of major cardiovascular diseases and nonvascular mortality: an individual participant meta-analysis. JAMA. 2005; 294(14):1799-1809. PubMedhttps://doi.org/10.1001/jama.294.14.1799Google Scholar
- Zhang Y, Zhu C-G, Guo Y-L. Higher fibrinogen level is independently linked with the presence and sseverity of new-onset coronary atherosclerosis among Han Chinese population. PLoS One. 2014; 9(11):e113460. Google Scholar
- Machlus KR, Cardenas JC, Church FC. Causal relationship between hyperfibrinogenemia, thrombosis, and resistance to thrombolysis in mice. Blood. 2011; 117(18):4953-4963. PubMedhttps://doi.org/10.1182/blood-2010-11-316885Google Scholar
- Lowe GDO. Fibrinogen assays for cardiovascular risk assessment. Clin Chem. 2010; 56(5):693-695. PubMedhttps://doi.org/10.1373/clinchem.2010.145342Google Scholar
- Sarker H, Hardy E, Haimour A. Identification of fibrinogen as a natural inhibitor of MMP-2. Sci Rep. 2019; 9(1):4340. Google Scholar
- Sabater-Lleal M, Huang J, Chasman D. Multiethnic meta-analysis of genome-wide association studies in >100 000 subjects identifies 23 fibrinogen-associated loci but no strong evidence of a causal association between circulating fibrinogen and cardiovascular disease. Circulation. 2013; 128(12):1310-1324. PubMedhttps://doi.org/10.1161/CIRCULATIONAHA.113.002251Google Scholar
- Ward-Caviness CK, de Vries PS, Wiggins KL. Mendelian randomization evaluation of causal effects of fibrinogen on incident coronary heart disease. PLoS One. 2019; 14(5):e0216222. Google Scholar
- Lovely RS, Falls LA, Al-Mondhiry HA. Association of gammaA/gamma’ fibrinogen levels and coronary artery disease. Thromb Haemost. 2002; 88(1):26-31. PubMedGoogle Scholar
- Omarova F, Uitte de Willige S, Simioni P. Fibrinogen g’ increases the sensitivity to activated protein C in normal and factor V Leiden plasma. Blood. 2014; 124(9):1531-1538. PubMedhttps://doi.org/10.1182/blood-2014-02-554055Google Scholar
- Macrae FL, Domingues MM, Casini A. The (patho)physiology of fibrinogen γ’. Semin Thromb Hemost. 2016; 42(4):344-355. Google Scholar
- Nowak-Gottl U, Weiler H, Hernandez I. Fibrinogen alpha and gamma genes and factor VLeiden in children with thromboembolism: results from 2 family-based association studies. Blood. 2009; 114(9):1947-1953. PubMedhttps://doi.org/10.1182/blood-2009-04-218727Google Scholar
- Uitte de Willige S, de Visser MC, Houwing-Duistermaat JJ. Genetic variation in the fibrinogen gamma gene increases the risk for deep venous thrombosis by reducing plasma fibrinogen gamma’ levels. Blood. 2005; 106(13):4176-4183. PubMedhttps://doi.org/10.1182/blood-2005-05-2180Google Scholar
- Cheung EY, Uitte de Willige S, Vos HL. Fibrinogen gamma’ in ischemic stroke: a case-control study. Stroke. 2008; 39(3):1033-1035. PubMedhttps://doi.org/10.1161/STROKEAHA.107.495499Google Scholar
- Uitte de Willige S, Doggen CJ, MC DEV. Haplotypes of the fibrinogen gamma gene do not affect the risk of myocardial infarction. J Thromb Haemost. 2006; 4(2):474-476. PubMedhttps://doi.org/10.1111/j.1538-7836.2006.01716.xGoogle Scholar
- Soria J, Mirshahi S, Mirshahi SQ. Fibrinogen αC domain: its importance in physiopathology. Res Pract Thromb Haemost. 2019; 3(2):173-183. Google Scholar
- de Maat MP, Verschuur M. Fibrinogen heterogeneity: inherited and noninherited. Curr Opin Hematol. 2005; 12(5):377-383. PubMedhttps://doi.org/10.1097/01.moh.0000169287.51594.3bGoogle Scholar
- Carter AM, Catto AJ, Kohler HP. alpha-fibrinogen Thr312Ala polymorphism and venous thromboembolism. Blood. 2000; 96(3):1177-1179. PubMedGoogle Scholar
- Morris TA, Marsh JJ, Chiles PG. High prevalence of dysfibrinogenemia among patients with chronic thromboembolic pulmonary hypertension. Blood. 2009; 114(9):1929-1936. PubMedhttps://doi.org/10.1182/blood-2009-03-208264Google Scholar
- Planquette B, Sanchez O, Marsh JJ. Fibrinogen and the prediction of residual obstruction manifested after pulmonary embolism treatment. Eur Respir J. 2018; 52(5):1801467. PubMedhttps://doi.org/10.1183/13993003.01467-2018Google Scholar
- Stec JJ, Silbershatz H, Tofler GH. Association of fibrinogen with cardiovascular risk factors and cardiovascular disease in the Framingham Offspring Population. Circulation. 2000; 102(14):1634-1638. PubMedhttps://doi.org/10.1161/01.CIR.102.14.1634Google Scholar
- Simpson-Haidaris PJ, Rybarczyk B. Tumors and fibrinogen. Ann N Y Acad Sci. 2001; 936(1):406-425. PubMedGoogle Scholar
- Perisanidis C, Psyrri A, Cohen EE. Prognostic role of pretreatment plasma fibrinogen in patients with solid tumors: a systematic review and meta-analysis. Cancer Treat Rev. 2015; 41(10):960-970. Google Scholar
- Wada H, Mori Y, Okabayashi K. High plasma fibrinogen level is associated with poor clinical outcome in DIC patients. Am J Hematol. 2003; 72(1):1-7. PubMedhttps://doi.org/10.1002/ajh.10249Google Scholar
- Dai K, Zhang Q, Li Y. Plasma fibrinogen levels correlate with prognosis and treatment outcome in patients with non-M3 acute myeloid leukemia. Leuk Lymphoma. 2019; 60(6):1503-1511. Google Scholar
- Elmoamly S, Afif A. Can biomarkers of coagulation, platelet activation, and inflammation predict mortality in patients with hematological malignancies?. Hematology. 2018; 23(2):89-95. Google Scholar
- Palumbo JS, Kombrinck KW, Drew AF. Fibrinogen is an important determinant of the metastatic potential of circulating tumor cells. Blood. 2000; 96(10):3302-3309. PubMedGoogle Scholar
- Adams GN, Rosenfeldt L, Frederick M. Colon cancer growth and dissemination relies upon thrombin, stromal PAR-1, and fibrinogen. Cancer Res. 2015; 75(19):4235-4243. PubMedhttps://doi.org/10.1158/0008-5472.CAN-15-0964Google Scholar
- Sahni A, Simpson-Haidaris PJ, Sahni SK. Fibrinogen synthesized by cancer cells augments the proliferative effect of fibroblast growth factor-2 (FGF-2). J Thromb Haemost. 2008; 6(1):176-183. PubMedGoogle Scholar
- Roche Y, Pasquier D, Rambeaud JJ. Fibrinogen mediates bladder cancer cell migration in an ICAM-1-dependent pathway. Thromb Haemost. 2003; 89(6):1089-1097. PubMedGoogle Scholar
- Zheng S, Shen J, Jiao Y. Platelets and fibrinogen facilitate each other in protecting tumor cells from natural killer cytotoxicity. Cancer Sci. 2009; 100(5):859-865. PubMedhttps://doi.org/10.1111/j.1349-7006.2009.01115.xGoogle Scholar
- Jennewein C, Tran N, Paulus P. Novel aspects of fibrin(ogen) fragments during inflammation. Mol Med. 2011; 17(5-6):568-573. PubMedhttps://doi.org/10.2119/molmed.2010.00146Google Scholar
- Sweeney MD, Kisler K, Montagne A. The role of brain vasculature in neurodegen-erative disorders. Nat Neurosci. 2018; 21(10):1318-1331. PubMedhttps://doi.org/10.1038/s41593-018-0234-xGoogle Scholar
- Daneman R, Prat A. The blood-brain barrier. Cold Spring Harb Perspect Biol. 2015; 7(1):a020412. PubMedhttps://doi.org/10.1101/cshperspect.a020412Google Scholar
- Petersen MA, Ryu JK, Akassoglou K. Fibrinogen in neurological diseases: mechanisms, imaging and therapeutics. Nat Rev Neurosci. 2018; 19(5):283-301. Google Scholar
- Bowman GL, Kaye JA, Moore M. Blood-brain barrier impairment in Alzheimer disease: stability and functional significance. Neurology. 2007; 68(21):1809-1814. PubMedhttps://doi.org/10.1212/01.wnl.0000262031.18018.1aGoogle Scholar
- Ujiie M, Dickstein DL, Carlow DA. Blood-brain barrier permeability precedes senile plaque formation in an Alzheimer disease model. Microcirculation. 2003; 10(6):463-470. PubMedhttps://doi.org/10.1038/sj.mn.7800212Google Scholar
- Reich DS, Lucchinetti CF, Calabresi PA. Multiple sclerosis. N Engl J Med. 2018; 378(2):169-180. PubMedhttps://doi.org/10.1056/NEJMra1401483Google Scholar
- Marik C, Felts PA, Bauer J. Lesion genesis in a subset of patients with multiple sclerosis: a role for innate immunity?. Brain. 2007; 130(Pt 11):2800-2815. PubMedhttps://doi.org/10.1093/brain/awm236Google Scholar
- Hultman K, Strickland S, Norris EH. The APOE e4/e4 genotype potentiates vascular fibrin(ogen) deposition in amyloid-laden vessels in the brains of Alzheimer’s disease patients. J Cereb Blood Flow Metab. 2013; 33(8):1251-1258. PubMedhttps://doi.org/10.1038/jcbfm.2013.76Google Scholar
- Ryu JK, McLarnon JG. A leaky blood-brain barrier, fibrinogen infiltration and microglial reactivity in inflamed Alzheimer’s disease brain. J Cell Mol Med. 2009; 13(9a):2911-2925. PubMedhttps://doi.org/10.1111/j.1582-4934.2008.00434.xGoogle Scholar
- Fiala M, Liu QN, Sayre J. Cyclooxygenase-2-positive macrophages infiltrate the Alzheimer’s disease brain and damage the blood-brain barrier. Eur J Clin Invest. 2002; 32(5):360-371. PubMedhttps://doi.org/10.1046/j.1365-2362.2002.00994.xGoogle Scholar
- Miners JS, Schulz I, Love S. Differing associ ations between Aβ accumulation, hypoper-fusion, blood-brain barrier dysfunction and loss of PDGFRB pericyte marker in the pre-cuneus and parietal white matter in Alzheimer’s disease. J Cereb Blood Flow Metab. 2018; 38(1):103-115. Google Scholar
- Cortes-Canteli M, Mattei L, Richards AT. Fibrin deposited in the Alzheimer’s disease brain promotes neuronal degeneration. Neurobiol Aging. 2015; 36(2):608-617. PubMedhttps://doi.org/10.1016/j.neurobiolaging.2014.10.030Google Scholar
- Davalos D, Akassoglou K. Fibrinogen as a key regulator of inflammation in disease. Semin Immunopathol. 2012; 34(1):43-62. PubMedhttps://doi.org/10.1007/s00281-011-0290-8Google Scholar
- Ryu JK, Petersen MA, Murray SG. Blood coagulation protein fibrinogen promotes autoimmunity and demyelination via chemokine release and antigen presentation. Nat Commun. 2015; 6:8164. PubMedhttps://doi.org/10.1038/ncomms9164Google Scholar
- Merlini M, Rafalski VA, Rios Coronado PE. Fibrinogen induces microglia-mediated spine elimination and cognitive impairment in an Alzheimer’s disease model. Neuron. 2019; 101(6):1099-1108. Google Scholar
- Zamolodchikov D, Renne T, Strickland S. The Alzheimer’s disease peptide β-amyloid promotes thrombin generation through activation of coagulation factor XII. J Thromb Haemost. 2016; 14(5):995-1007. PubMedhttps://doi.org/10.1111/jth.13209Google Scholar
- Zamolodchikov D, Strickland S. Aβ delays fibrin clot lysis by altering fibrin structure and attenuating plasminogen binding to fibrin. Blood. 2012; 119(14):3342-3351. PubMedhttps://doi.org/10.1182/blood-2011-11-389668Google Scholar
- Petersen MA, Ryu JK, Chang KJ. Fibrinogen activates BMP signaling in oligo-dendrocyte progenitor cells and inhibits remyelination after vascular damage. Neuron. 2017; 96(5):1003-1012. Google Scholar
- Davalos D, Kyu Ryu J, Merlini M. Fibrinogen-induced perivascular microglial clustering is required for the development of axonal damage in neuroinflammation. Nat Commun. 2012; 3:1227. PubMedhttps://doi.org/10.1038/ncomms2230Google Scholar
- Akassoglou K, Yu WM, Akpinar P. Fibrin inhibits peripheral nerve remyelination by regulating Schwann cell differentiation. Neuron. 2002; 33(6):861-875. PubMedhttps://doi.org/10.1016/S0896-6273(02)00617-7Google Scholar
- Schachtrup C, Lu P, Jones LL. Fibrinogen inhibits neurite outgrowth via beta 3 integrin-mediated phosphorylation of the EGF receptor. Proc Natl Acad Sci U S A. 2007; 104(28):11814-11819. PubMedhttps://doi.org/10.1073/pnas.0704045104Google Scholar
- Schachtrup C, Ryu JK, Helmrick MJ. Fibrinogen triggers astrocyte scar formation by promoting the availability of active TGF-beta after vascular damage. J Neurosci. 2010; 30(17):5843-5854. PubMedhttps://doi.org/10.1523/JNEUROSCI.0137-10.2010Google Scholar
- Montagne A, Nikolakopoulou AM, Zhao Z. Pericyte degeneration causes white matter dysfunction in the mouse central nervous system. Nat Med. 2018; 24(3):326-337. https://doi.org/10.1038/nm.4482Google Scholar
- Zou T, Ling C, Xiao Y. Exogenous tissue plasminogen activator enhances peripheral nerve regeneration and functional recovery after injury in mice. J Neuropathol Exp Neurol. 2006; 65(1):78-86. Google Scholar
- Ugarova TP, Lishko VK, Podolnikova NP. Sequence g377−395(P2), but not g190−202(P1), is the binding site for the αMI-domain of integrin αMβ2 in the γC-domain of fibrinogen. Biochemistry. 2003; 42(31):9365-9373. PubMedhttps://doi.org/10.1021/bi034057kGoogle Scholar
- Ryu JK, Rafalski VA, Meyer-Franke A. Fibrin-targeting immunotherapy protects against neuroinflammation and neurodegeneration. Nat Immunol. 2018; 19(11):1212-1223. Google Scholar
- van Oijen M, Witteman JC, Hofman A. Fibrinogen is associated with an increased risk of Alzheimer disease and vascular dementia. Stroke. 2005; 36(12):2637-2641. PubMedhttps://doi.org/10.1161/01.STR.0000189721.31432.26Google Scholar
- Pedersen A, Stanne TM, Redfors P. Fibrinogen concentrations predict long-term cognitive outcome in young ischemic stroke patients. Res Pract Thromb Haemost. 2018; 2(2):339-346. Google Scholar
- Bijak M, Olejnik A, Rokita B. Increased level of fibrinogen chains in the proteome of blood platelets in secondary progressive multiple sclerosis patients. J Cell Mol Med. 2019; 23(5):3476-3482. Google Scholar
- Negron O, Flick MJ. Does fibrinogen serve the host or the microbe in Staphylococcus infection?. Curr Opin Hematol. 2019; 26(5):343-348. Google Scholar
- Landers CT, Tung HY, Knight JM. Selective fibrinogen cleavage by diverse proteinases initiates innate allergic and antifungal immunity through CD11b. J Biol Chem. 2019; 294(22):8834-8847. PubMedhttps://doi.org/10.1074/jbc.RA118.006724Google Scholar
- Liesenborghs L, Meyers S, Lox M. Staphylococcus aureus endocarditis: distinct mechanisms of bacterial adhesion to damaged and inflamed heart valves. Eur Heart J. 2019; 40(39):3248-3259. Google Scholar
- Watve MG, Tickoo R, Jog MM. How many antibiotics are produced by the genus Streptomyces?. Arch Microbiol. 2001; 176(5):386-390. PubMedhttps://doi.org/10.1007/s002030100345Google Scholar
- Yike I. Fungal proteases and their pathophysiological effects. Mycopathologia. 2011; 171(5):299-323. PubMedhttps://doi.org/10.1007/s11046-010-9386-2Google Scholar
- Barrera V, Skorokhod OA, Baci D. Host fibrinogen stably bound to hemozoin rapidly activates monocytes via TLR-4 and CD11b/CD18-integrin: a new paradigm of hemozoin action. Blood. 2011; 117(21):5674-5682. PubMedhttps://doi.org/10.1182/blood-2010-10-312413Google Scholar
- Ling GS, Bennett J, Woollard KJ. Integrin CD11b positively regulates TLR4- induced signalling pathways in dendritic cells but not in macrophages. Nat Commun. 2014; 5:3039. PubMedhttps://doi.org/10.1038/ncomms4039Google Scholar
- Colvin RB, Mosesson MW, Dvorak HF. Delayed-type hypersensitivity skin reactions in congenital afibrinogenemia lack fibrin deposition and induration. J Clin Invest. 1979; 63(6):1302-1306. PubMedhttps://doi.org/10.1172/JCI109425Google Scholar
- Lumeng CN, Saltiel AR. Inflammatory links between obesity and metabolic disease. J Clin Invest. 2011; 121(6):2111-2117. PubMedhttps://doi.org/10.1172/JCI57132Google Scholar
- Morange PE, Alessi MC. Thrombosis in central obesity and metabolic syndrome: mechanisms and epidemiology. Thromb Haemost. 2013; 110(4):669-680. PubMedhttps://doi.org/10.1160/TH13-01-0075Google Scholar
- Stalls CM, Triplette MA, Viera AJ. The association between body mass index and coronary artery disease severity: a comparison of black and white patients. Am Heart J. 2014; 167(4):514-520. Google Scholar
- Avellone G, di Garbo V, Cordova R. Effects of heparin treatment on hemostatic abnormalities in obese non-insulin-dependent diabetic patients. Metabolism. 1997; 46(8):930-934. PubMedhttps://doi.org/10.1016/S0026-0495(97)90082-2Google Scholar
- Handley DA, Hughes TE. Pharmacological approaches and strategies for therapeutic modulation of fibrinogen. Thromb Res. 1997; 87(1):1-36. PubMedhttps://doi.org/10.1016/S0049-3848(97)00091-1Google Scholar
- De Feo P, Volpi E, Lucidi P. Physiological increments in plasma insulin concentrations have selective and different effects on synthesis of hepatic proteins in normal humans. Diabetes. 1993; 42(7):995-1002. PubMedhttps://doi.org/10.2337/diab.42.7.995Google Scholar
- De Feo P, Gaisano MG, Haymond MW. Differential effects of insulin deficiency on albumin and fibrinogen synthesis in humans. J Clin Invest. 1991; 88(3):833-840. PubMedhttps://doi.org/10.1172/JCI115384Google Scholar
- Undas A, Ariens RA. Fibrin clot structure and function: a role in the pathophysiology of arterial and venous thromboembolic diseases. Arterioscler Thromb Vasc Biol. 2011; 31(12):e88-e99. PubMedhttps://doi.org/10.1161/ATVBAHA.111.230631Google Scholar
- Kopec AK, Abrahams SR, Thornton S. Thrombin promotes diet-induced obesity through fibrin-driven inflammation. J Clin Invest. 2017; 127(8):3152-3166. Google Scholar
- Flick MJ, Du X, Witte DP. Leukocyte engagement of fibrin(ogen) via the integrin receptor alphaMbeta2/Mac-1 is critical for host inflammatory response in vivo. J Clin Invest. 2004; 113(11):1596-1606. PubMedhttps://doi.org/10.1172/JCI200420741Google Scholar
- Glenner GG. Amyloid deposits and amyloidosis. The beta-fibrilloses (first of two parts). N Engl J Med. 1980; 302(23):1283-1292. PubMedhttps://doi.org/10.1056/NEJM198006053022305Google Scholar
- Hol PR, Snel FW, Niewold TA. Amyloid-enhancing factor (AEF) in the pathogenesis of AA-amyloidosis in the hamster. Virchows Arch B Cell Pathol Incl Mol Pathol. 1986; 52(3):273-281. PubMedGoogle Scholar
- Page MJ, Thomson GJA, Nunes JM. Serum amyloid A binds to fibrin(ogen), promoting fibrin amyloid formation. Sci Rep. 2019; 9(1):3102. https://doi.org/10.1038/s41598-019-39056-xGoogle Scholar
- Uemichi T, Liepnieks JJ, Yamada T. A frame shift mutation in the fibrinogen A alpha chain gene in a kindred with renal amyloidosis. Blood. 1996; 87(10):4197-4203. PubMedGoogle Scholar
- Stangou AJ, Banner NR, Hendry BM. Hereditary fibrinogen A alpha-chain amyloidosis: phenotypic characterization of a systemic disease and the role of liver transplantation. Blood. 2010; 115(15):2998-3007. PubMedhttps://doi.org/10.1182/blood-2009-06-223792Google Scholar
- Picken MM. Fibrinogen amyloidosis: the clot thickens!. Blood. 2010; 115(15):2985-2986. PubMedhttps://doi.org/10.1182/blood-2009-12-236810Google Scholar