Factor XIII Val34Leu variant protects against coronary artery disease

The History of Factor XIII Deficiency

Despite the early discovery of factor XIII (FXIII) in 1944, the diagnosis of FXIII deficiency was not made until 1960, after all the other coagulation factor deficiencies, most likely due to the normality of routine coagulation testing in FXIII deficiency. Although the first case was detected by the clot solubility test and this test has long since been used to detect FXIII deficiency, the test is no longer recommended by experts. Over the past 60 years, knowledge about FXIII deficiency has expanded considerably, between 1992, when the first variant was identified, and 2022, 197 mutations have been reported. Almost all missense mutations have a similar effect on FXIII, leading to instability and faster degradation of mutant FXIII protein. Therapeutic options have evolved from historical fresh frozen plasma (FFP), old plasma, whole blood, and cryoprecipitate, to plasma-derived and recombinant FXIII concentrates, respectively available since 1993 and 2012. These concentrate products were respectively approved by the Food and Drug Administration in 2011 and 2013. This historical review covers various aspects of FXIII related disorders, including the discovery of the FXIII, associated disorders, molecular basis, diagnosis, and treatment of FXIII deficiency.

Association of factor V Leiden R506Q, FXIIIVal34Leu, and MTHFR C677T polymorphisms with acute myocardial infarction

Background

Acute myocardial infarction (AMI) is a leading cause of death and morbidity around the world. Although the association between thrombophilia and AMI is well-established, controversial data are present on the association between thrombophilic polymorphisms and AMI. The aim of this study was to investigate the association of three thrombophilic polymorphisms including factor V Leiden (FVL), MTHFRC677T (methylenetetrahydrofolate reductase), and Coagulation factor XIIIVal34Leu with AMI in East of Iran.

Result

There were no statistically significant differences between the patients and control groups in terms of the distributions of allelic and genotypic frequencies of FVL and FXIIIVal34Leu polymorphisms (P-value > 0.05). Subjects who carried CT genotype of MTHFR C677T polymorphism were at a 2.03-fold higher risk for AMI (P-value: 0.02, OR 1.76, 95% CI 1.07–2.75). Furthermore, patients with MTHFR 677CT (P-value < 0.001, β = - 0.90, 95% CI − 1.33, − 047) or 677CC (P-value < 0.001, β = - 1.04, 95% CI − 1.47, − 0.61) genotypes showed significantly Lower creatinine levels compared with patients having the MTHFR 677TT. No association was observed between the other remaining polymorphisms and AMI (P-value > 0.05).

Conclusion

Our findings showed that MTHFRC677T polymorphism could contribute to AMI susceptibility and increase creatinine levels in east Iran population. This was the first study to examine the association of these three polymorphisms with AMI in east Iran.

Decreased clot burden is associated with factor XIII Val34Leu polymorphism and better functional outcomes in acute ischemic stroke patients treated with intravenous thrombolysis

BACKGROUND

Intravenous thrombolysis using recombinant tissue plasminogen activator remains the mainstay treatment of acute ischemic stroke (AIS), although endovascular treatment is becoming standard of care in case of large vessel occlusions (LVO). To quantify the thrombus burden in LVO, a semiquantitative CT angiography (CTA) grading system, the clot burden score (CBS) can be used. Here we aimed to study the association between CBS and various hemostasis parameters, and to evaluate which parameters are major determinants of thrombolysis outcome.

METHODS

In this single-centered prospective observational case-control study, 200 anterior circulation AIS patients receiving intravenous thrombolysis treatment without thrombectomy were enrolled: 100 AIS patients with LVO (CBS 0-9) and 100 age- and sex-matched AIS patients without LVO (CBS 10). Fibrinogen, α2-plasmin inhibitor, plasminogen, factor XIII and D-dimer were assessed from blood samples taken before and 24 h after thrombolysis, and FXIII-A Val34Leu was genotyped. CBS was calculated using admission CTA. Short-term outcomes were defined based on the change in NIHSS by day 7, long-term outcomes were assessed according to the modified Rankin scale at 3 months post-event.

RESULTS

Poor outcomes were significantly more frequent in the CBS 0-9 group. Plasminogen activity on admission was significantly higher in the CBS 0-9 group. In a univariate analysis, significant protective effect of the Leu34 allele against developing larger clots (CBS 0-9) could be demonstrated (OR:0.519; 95%CI:0.298-0.922, p = 0.0227). Multivariate regression analysis revealed that CBS is an independent predictor of short- and long-term functional outcomes, while such effect of the studied hemostasis parameters could not be demonstrated.

CONCLUSIONS

CBS was found to be a significant independent predictor of thrombolysis outcomes. FXIII-A Leu34 carrier status was associated with smaller thrombus burden, which is consistent with the in vitro described whole blood clot mass reducing effects of the allele, but the polymorphism had no effect on thrombolysis outcomes.

The factor XIII-A Val34Leu polymorphism decreases whole blood clot mass at high fibrinogen concentrations

BACKGROUND

Factor XIII (FXIII) promotes fibrin crosslinking and red blood cell (RBC) retention in clots. The FXIII-A polymorphism, Val34Leu, is associated with protection against venous thrombosis. This effect is hypothesized to result from fibrinogen concentration-dependent changes in fibrin structure. Effects of the FXIII-A Val34Leu polymorphism in whole blood clots have not been investigated.

AIM

Characterize effects of FXIII-A Val34Leu polymorphism and fibrinogen on whole blood clots.

METHODS

We isolated platelet-poor plasmas from human donors (FXIIIVal/Val , FXIIIVal/Leu , FXIIILeu/Leu ), reconstituted plasmas with platelets and RBCs, and triggered clotting. We assessed contributions of gender, age, clotting times, thrombin generation, FXIII activity, FXIII-A Val34Leu polymorphism, and fibrinogen to clot mass. We also reconstituted FXIII-depleted plasma with platelets, RBCs, and purified FXIIIVal/Val or FXIIILeu/Leu , varied fibrinogen, and characterized effects on clot mass.

RESULTS

Clot mass was associated with age, fibrinogen, prothrombin time, and thrombin generation. Clots reconstituted with plasmas from individuals with FXIII-AVal/Val and FXIII-AVal/Leu did not differ in mass from clots with FXIII-ALeu/Leu . However, clots containing a 34Val allele demonstrated a fibrinogen concentration-dependent increase in mass, whereas clots with homozygous 34Leu did not. In plasmas with high fibrinogen, mass was higher for clots with 34Val alleles compared with clots with homozygous 34Leu. In clots reconstituted with purified FXIII, increasing fibrinogen enhanced clot mass in the presence of 34Val, but decreased mass in the presence of 34Leu.

CONCLUSIONS

FXIII 34Leu mitigates the effect of elevated fibrinogen on whole blood clot mass. The Val34Leu polymorphism may protect against venous thrombosis by reducing clot mass.

Tocilizumab Effects on Coagulation Factor XIII in Patients with Rheumatoid Arthritis

Introduction

Rheumatoid arthritis (RA) is a chronic systemic auto-immune disease associated with a prothrombotic state. Tocilizumab, an interleukin-6 receptor inhibitor, is highly effective in controlling disease activity and thrombotic risk. Factor XIII (FXIII), involved in thrombotic complications, has been reported to be reduced in RA patients during maintenance treatment with tocilizumab, but no data are available before and after the drug administration. Thus, we investigated the effects of tocilizumab on FXIII, thrombin generation and inflammation in patients with RA naïve for the drug.

Methods

We studied 15 consecutive adult patients with RA at baseline and 4 weeks after the onset of parenteral administration of tocilizumab, measuring disease activity and plasma levels of C-reactive protein (CRP), FXIII, and prothrombin fragments F1+2 by immunoenzymatic methods. Fifteen healthy subjects, sex-and age-matched with patients, served as normal controls for laboratory measurements.

Results

At baseline, patients with established RA had a median DAS28 of 4.8 (3.2–8.3) and, compared to healthy controls, had higher plasma levels of CRP (p < 0.0001), FXIII (p = 0.017) and F1+2 (p < 0.0001). Four weeks after starting treatment with tocilizumab, based on the EULAR response criteria, eight patients were classifiable as responders and seven as non-responders. In responders, we observed a statistically significant reduction not only of the values of DAS28 and CRP (p = 0.012 for both), ut also of plasma levels of FXIII (p = 0.05) and F1+2 (p = 0.025). In non-responders, all the studied parameters were unchanged.

Conclusion

The decrease of FXIII and F1+2 levels after tocilizumab treatment observed only in those patients who responded to the drug indicates that the effect of tocilizumab on the prothrombotic state is linked to the control of inflammation and disease activity and not to a direct effect of the drug, thus contributing to the reduction of the cardiovascular risk.

Factor XIII expression within aortic valves and its plasma activity in patients with aortic stenosis: association with severity of disease

Aortic valve stenosis (AS) shares several similarities with atherosclerosis. Factor XIII (FXIII) has been detected within atherosclerotic plaques and may contribute to the development of atherosclerosis via multiple mechanisms. In the current study, we sought to investigate FXIII expression within human stenotic aortic valves and its association with severity of the disease. We prospectively enrolled 91 consecutive patients with AS scheduled for isolated valve replacement. Valvular FXIII subunit A (FXIII-A), fibrin and macrophages expression was evaluated by immunostaining. FXIII-A subunit transcripts and FXIII-A Val34Leu polymorphism was determined by real-time PCR. Plasma FXIII (pFXIII) activity was measured. We demonstrated that the valvular FXIII-A was predominantly expressed on the aortic side of leaflets, colocalized with alternatively activated macrophages (AAM). Areas stained for FXIII-A showed positive correlations with valvular fibrin presence, degree of calcification, pFXIII activity and the severity of AS, reflected by mean and maximum transvalvular gradients (all, p<0.001). The FXIII-A mRNA in the stenotic leaflets was significantly elevated compared to control leaflets. Interestingly, pFXIII activity was also positively correlated with mean (p<0.001) and maximum (p=0.001) transvalvular gradient. The FXIII-A Val34Leu polymorphism did not affect FXIII-A and fibrin expression in AS valves. In conclusion, the study is the first to show abundant expression of FXIII-A at the mRNA and protein levels within human stenotic aortic valves, which is associated with the severity of AS. Our findings might suggest that FXIII in the stenotic valves is presented in AAM and may be involved in the AS progression.

The relevance of coagulation in cardiovascular disease: what do the biomarkers tell us?

Several haemostatic factors have been associated with incident arterial cardiovascular disease in prospective studies and meta-analyses. Plasma fibrinogen shows a strong and consistent association with risk; however, this may reflect its inflammatory marker status, and causality remains to be proven. The common haemostatic gene polymorphisms for factor II, factor V and the von Willebrand factor: Factor VIII (non-O blood group) show significant associations with coronary heart disease (CHD) risk, consistent with potential causality. Increased D-dimer and t-PA antigen levels are associated with CHD risk, suggesting roles for coagulation activation and endothelial disturbance. There is little evidence for associations with CVD with other haemostatic factors.

Association of genetic variants of hemostatic genes with myocardial infarction in Egyptian patients

Hemostatic genes polymorphisms are well known to be associated with venous thrombosis, but their association with arterial thrombosis especially myocardial infarction (MI) remains to be clarified. We investigated the role of three hemostatic gene polymorphisms, prothrombin G20210A, factor XIII (FXIII) Val34Leu (G/T), and fibrinogen-β-455G/A and their coexistence in Egyptian patients with MI. The possible correlation of these polymorphisms with plasma fibrinogen level was also evaluated. The study included 120 patients with MI and 60 healthy volunteers. Gene polymorphisms were tested using multiplex polymerase chain reaction and reverse-hybridization technique. Plasma fibrinogen level was determined by ELISA. Our study showed an increased risk of MI with fibrinogen β-455G/A heterozygosity as well as FXIII Val34Leu homo and heterozygosity. In addition, the FXIII T allele (Leu34) and fibrinogen β-455A allele were significantly associated with MI. Conversely, the prevalence of prothrombin mutation did not differ between patients with MI and controls. Combined carriers of FXIII Leu34 and fibrinogen-β455A alleles were at higher risk of MI, whereas combined FXIII Val34Leu and prothrombin 20210A polymorphisms did not show increased risk for MI compared with controls. Plasma fibrinogen levels were significantly higher in patients with MI than controls. In MI patients, plasma fibrinogen levels were significantly higher in those with FXIII GT/TT or fibrinogen β-455 GA, while were significantly lower in those with prothrombin 20210 GA compared with patients with wild type genotypes. In conclusion, our results suggest a possible thrombotic predisposition of FXIII Val34Leu, fibrinogen β-455G/A polymorphisms and their coexistence for MI. These polymorphisms may add complexity to disease pathology by increasing plasma fibrinogen level. Extended studies are needed to confirm our results; nevertheless, these data may be implicated in genetic counseling and screening of high-risk individuals.

Screening cleavage of Factor XIII V34X Activation Peptides by thrombin mutants: A strategy for controlling fibrin architecture

In blood coagulation, thrombin converts fibrinogen into fibrin monomers that polymerize into a clot network. Thrombin also activates Factor XIII by cleaving the R37-G38 peptide bond of the Activation Peptide (AP) segment. The resultant transglutaminase introduces covalent crosslinks into the fibrin clot. A strategy to modify clot architecture would be to design FXIII AP sequences that are easier or more difficult to be thrombin-cleaved thus controlling initiation of crosslinking. To aid in this design process, FXIII V34X (28-41) Activation Peptides were kinetically ranked for cleavage by wild-type thrombin and several anticoagulant mutants. Thrombin-catalyzed hydrolysis of aromatic FXIII F34, W34, and Y34 APs was compared with V34 and L34. Cardioprotective FXIII L34 remained the variant most readily cleaved by wild-type thrombin. The potent anticoagulant thrombins W215A and W215A/E217A (missing a key substrate platform for binding fibrinogen) were best able to hydrolyze FXIII F34 and W34 APs. Thrombin I174A and L99A could effectively accommodate FXIII W34 and Y34 APs yielding kinetic parameters comparable to FXIII AP L34 with wild-type thrombin. None of the aromatic FXIII V34X APs could be hydrolyzed by thrombin Y60aA. FXIII F34 and W34 are promising candidates for FXIII - anticoagulant thrombin systems that could permit FXIII-catalyzed crosslinking in the presence of reduced fibrin formation. By contrast, FXIII Y34 with thrombin (Y60aA or W215A/E217A) could help assure that both fibrin clot formation and protein crosslinking are hindered. Regulating the activation of FXIII is predicted to be a strategy for helping to control fibrin clot architecture and its neighboring environments.

Factor XIII A-Subunit V34L Variant Affects Thrombus Cross-Linking in a Murine Model of Thrombosis

OBJECTIVE

Factor XIII (FXIII) cross-links fibrin upon activation by thrombin. Activation involves cleavage at residue 37 by thrombin, releasing an activation peptide. A common polymorphism (valine to leucine variant at residue 34, V34L), located in the activation peptide, has been associated with increased activation rates and paradoxically a protective effect in cardiovascular disease. There is, currently, no data available on the effects of V34L from in vivo models of thrombosis. We examined the effect of FXIII V34L on clot formation and cross-linking in vivo.

APPROACH AND RESULTS

We generated a panel of full-length recombinant human FXIII-A2 variants with amino acid substitutions in the activation peptide to investigate the effect of these variants on activation rate, and we used wild-type, V34L, and alanine to glycine variant at residue 33 variants to study the effects of varying FXIII activation rate on thrombus formation in a murine model of FeCl3 injury. FXIII activation assay showed that residues 29, 30, 33, and 34 play a critical role in thrombin interaction. Full-length recombinant human FXIII-A2 V34L has significant effects on clot formation, structure, and lysis in vitro, using turbidity assay. This variant influenced fibrin cross-linking but not size of the thrombus in vivo.

CONCLUSIONS

Mutations in the activation peptide of full-length recombinant FXIII regulate activation rates by thrombin, and V34L influences in vivo thrombus formation by increased cross-linking of the clot.

Factor XIII-A subunit Val34Leu polymorphism in fatal atherothrombotic ischemic stroke

Factor XIII (FXIII) is a regulator of fibrinolysis and clot firmness. Val34Leu polymorphism of its potentially active A subunit (FXIII-A) leads to faster activation of FXIII, influences clot structure and provides a moderate protection against coronary artery disease. The effect of FXIII-A Val34Leu polymorphism on the risk of atherothrombotic ischemic stroke (AIS) has been investigated in a few studies with contradictory results. In all previous studies, only patients surviving AIS were enrolled and sex-specific effects were not explored. In this retrospective multicenter cohort, we investigated the effect of FXIII-A Val34Leu polymorphism on the risk of fatal AIS in women and men. DNA isolation and genetic determinations in the case of 316 patients who died of AIS were carried out on paraffin-embedded tissue specimens. Genetic analyses for population controls, patients with history of AIS and sex-matched controls were performed on extracted genomic DNA from peripheral blood leukocytes. The prevalence of homozygous wild-type, and heterozygous genotypes, Leu34 carriers and Leu34 allele was not different significantly between the patients with fatal AIS and their respective controls. Logistic regression analysis with age as co-variant demonstrated that in women, homozygous presentation of Leu34 allele represented a more than three-fold increased risk of AIS with fatal outcome. The results demonstrate that FXIII-A Val34Leu polymorphism does not influence the occurrence of AIS, but has an effect on the severity of its outcome. This effect is sex-specific and in homozygous women, the prothrombotic/antifibrinolytic effects of FXIII-A Val34Leu polymorphism seem to prevail.

Factor XIII Val34Leu polymorphism and recurrent myocardial infarction in patients with coronary artery disease

Factor XIII (FXIII) is necessary for cross linking of fibrin strands and generation of stable fibrin clot. FXIII Val34Leu is a common genetic single nucleotide polymorphism that has been associated with accelerated fibrin stabilization and reduced rate of fibrinolysis. The contribution of Val34Leu to long term risk of recurrent myocardial infarction (MI) in patients with coronary stenting has not been conclusively established. The objective of the study was to examine the effects of Val34Leu on fibrin generation, platelet aggregation, and long term clinical outcomes in patients with coronary artery disease treated with dual antiplatelet therapy. Patients with angiographically documented coronary artery disease who were treated with aspirin and clopidogrel were enrolled (n = 211). Light transmittance aggregometry and plasma fibrin clot formation using thrombelastography (TEG) were determined. Genotyping of Val34Leu was performed using Taqman assay. Clinical events during follow up were recorded. Homozygous carriers of 34 Leu variant had significantly shorter fibrin clot formation time as compared to wild type individuals (TEG K: 1.27 ± 0.3 vs. 1.68 ± 1.1 min, p = 0.011). The Val34Leu variant was associated with gene dose dependent increased risk of MI (log rank, p = 0.002) or occurrence of composite of MI and CV death (log rank, p = 0.005) with highest event rates observed in homozygous carriers of 34 Leu. In summary, FXIII Val34Leu polymorphism was associated with increased rate of fibrin stabilization in homozygous carriers of the variant and may increase risk of recurrent MI and death in patients with angiographically established coronary artery disease treated with dual antiplatelet therapy.

Factor XIII-A dynamics in acute myocardial infarction: a novel prognostic biomarker?

After acute myocardial infarction (MI) the damaged heart has to be repaired. Factor XIII (FXIII) is considered a key molecule in promoting heart healing. FXIII deficiency was associated to cardiac rupture and anomalous remodelling in MI. During MI, FXIII contributes firstly to the intracoronary thrombus formation and shortly after to heal the myocardial lesion. To quantify the real contribution of FXIII in this process, and to explore its possible prognostic role, we monitored the FXIII-A subunit levels in 350 acute MI patients during the first six days (d0-d5) plus a control at 30-60 days (d30). A one-year follow-up was performed for all the patients. A transient drop in the FXIII-A mean level was noted in the whole cohort of patients (FXIII-Ad0 99.48 ± 30.5 vs FXIII-Ad5 76.51 ± 27.02; p< 0.0001). Interestingly, those who developed post-MI heart failure showed the highest drop (FXIII-Ad5 52.1 ± 25.2) and they already presented with low levels at recruitment. Similarly, those who died showed the same FXIII-A dynamic (FXIII-Ad5 54.0 ± 22.5). Conversely, patients who remained free of major adverse cardiac events, had lower consuming (FXIII-Ad0 103.6 ± 29.1 vs FXIII-Ad5 84.4 ± 24.5; p< 0.0001). Interestingly, the FXIII-A drop was independent from the amount of injury assessed by TnT and CKMB levels. The survival analysis ascribed an increased probability of early death or heart failure inversely related to FXIII-A quartiles (FXIII-A25th< 59.5 %; hazard ratio 4.25; 2.2-5.1; p< 0.0001). Different FXIII-A dynamics and levels could be utilised as early prognostic indicators during acute MI, revealing the individual potential to heal and suggesting tailored treatments to avoid heart failure or its extreme consequence.

Association of Hemostatic Gene Polymorphisms With Early-Onset Ischemic Heart Disease in Egyptian Patients

The association between hereditary thrombophilia and venous thrombosis is well established but controversial data exist with respect to arterial thrombosis. We performed a pilot study on 31 patients with acute myocardial infarction (AMI), 21 patients with unstable angina (UA), and 20 healthy volunteers to investigate the role of various hemostatic gene polymorphisms in young Egyptian patients, who survived their first ischemic heart disease (IHD). Thrombophilic gene polymorphisms were tested using multiplex polymerase chain reaction and reverse-hybridization technique. We showed an increased risk of AMI with factor V (FV) Leiden and prothrombin G20210A heterozygosity. The increased risks of UA was associated with GA and A allele of fibrinogen β-455G→A polymorphism. Conversely, factor XIII (FXIII) Val34Leu GT and T allele were protective in the UA group. Nevertheless, the prevalence of FV H1299R, plasminogen activator inhibitor 1 4G/5G, glycoprotein IIIa C1565T, 5,10-methylenetetrahydrofolate reductase C677T, and A1298C mutations did not differ between patients with IHD and controls. The data have clinical implications regarding screening and thromboprophylaxis in high-risk individuals younger than 40 years.

Factor XIII B subunit polymorphisms and the risk of coronary artery disease

The aim of the case-control study was to explore the effect of coagulation factor XIII (FXIII) B subunit (FXIII-B) polymorphisms on the risk of coronary artery disease, and on FXIII levels. In the study, 687 patients admitted for coronary angiography to investigate suspected coronary artery disease and 994 individuals representing the Hungarian population were enrolled. The patients were classified according to the presence of significant coronary atherosclerosis (CAS) and history of myocardial infarction (MI). The F13B gene was genotyped for p.His95Arg and for intron K nt29756 C>G polymorphisms; the latter results in the replacement of 10 C-terminal amino acids by 25 novel amino acids. The p.His95Arg polymorphism did not influence the risk of CAS or MI. The FXIII-B intron K nt29756 G allele provided significant protection against CAS and MI in patients with a fibrinogen level in the upper tertile. However, this effect prevailed only in the presence of the FXIII-A Leu34 allele, and a synergism between the two polymorphisms was revealed. Carriers of the intron K nt29756 G allele had significantly lower FXIII levels, and FXIII levels in the lower tertile provided significant protection against MI. It is suggested that the protective effect of the combined polymorphisms is related to decreased FXIII levels.

Effect of Factor XIII-A Val34Leu Polymorphism on Myocardial Infarction Risk

The association between factor XIII-A (FXIII-A) Val34Leu polymorphism and myocardial infarction (MI) risk remained controversial. We performed a meta-analysis. Online databases were searched. Twenty-eight studies were included. The FXIII-A Val34Leu polymorphism was significantly associated with MI risk (odds ratio (OR) = 0.83, 95% confidence interval [CI] 0.76-0.91; P < .0001). This result remained statistically significant when the adjusted ORs were combined (OR = 0.77, 95% CI 0.65-0.92; P = .004). When stratifying for race, this polymorphism showed decreased MI risk in Caucasians. In the subgroup analysis by age group, significant associations were observed in early-onset patients and in late-onset patients. In the subgroup analysis by gender, there was a significant association in women but not in men. In the subgroup analysis stratified by smoking status, MI risk was decreased in both smokers and nonsmokers. This study suggested that FXIIIA Val34Leu polymorphism was a protective factor for MI in caucasians.

Factor XIII, clot structure, thrombosis

Blood coagulation factor XIII (FXIII) is a tetrameric protein consisting of two catalytic A (FXIII-A) and two carrier/inhibitory B (FXIII-B) subunits. It is a zymogen, which becomes transformed into an active transglutaminase (FXIIIa) in the final phase of coagulation cascade by thrombin and Ca(2+). FXIII is essential for hemostasis, its deficiency results in severe bleeding diathesis. FXIIIa mechanically stabilizes fibrin by cross-linking its α-, and γ-chains. It also protects newly formed fibrin from fibrinolysis, primarily by cross-linking α(2)-plasmin inhibitor to fibrin. Beside the above prothrombotic effects, it is involved in limiting thrombus growth by down-regulating platelet adhesion to fibrin. Elevated FXIII level seems to be a gender-specific risk factor of both coronary artery disease and peripheral arterial disease, it represents an increased risk only in females. The association of FXIII level with the risk of ischemic stroke and venous thromboembolism was investigated only in a few studies from which no clear conclusion could be drawn. Among the FXIII subunit polymorphisms, concerning their effect on the risk of thrombotic diseases, only FXIII-A p.Val34Leu was investigated extensively. Meta-analyses of reported data suggest that this polymorphism provides a moderate protection against coronary artery disease and venous thromboembolism, but not against ischemic stroke. Gene-gene and gene-environmental interactions might modify its effect. Further studies are required to explore the effect of other FXIII subunit polymorphism on the risk of thrombotic diseases.

Factor XIII: a coagulation factor with multiple plasmatic and cellular functions

Factor XIII (FXIII) is unique among clotting factors for a number of reasons: 1) it is a protransglutaminase, which becomes activated in the last stage of coagulation; 2) it works on an insoluble substrate; 3) its potentially active subunit is also present in the cytoplasm of platelets, monocytes, monocyte-derived macrophages, dendritic cells, chondrocytes, osteoblasts, and osteocytes; and 4) in addition to its contribution to hemostasis, it has multiple extra- and intracellular functions. This review gives a general overview on the structure and activation of FXIII as well as on the biochemical function and downregulation of activated FXIII with emphasis on new developments in the last decade. New aspects of the traditional functions of FXIII, stabilization of fibrin clot, and protection of fibrin against fibrinolysis are summarized. The role of FXIII in maintaining pregnancy, its contribution to the wound healing process, and its proangiogenic function are reviewed in details. Special attention is given to new, less explored, but promising fields of FXIII research that include inhibition of vascular permeability, cardioprotection, and its role in cartilage and bone development. FXIII is also considered as an intracellular enzyme; a separate section is devoted to its intracellular activation, intracellular action, and involvement in platelet, monocyte/macrophage, and dendritic cell functions.

Fibrin clot structure and function: a role in the pathophysiology of arterial and venous thromboembolic diseases

The formation of fibrin clots that are relatively resistant to lysis represents the final step in blood coagulation. We discuss the genetic and environmental regulators of fibrin structure in relation to thrombotic disease. In addition, we discuss the implications of fibrin structure for treatment of thrombosis. Fibrin clots composed of compact, highly branched networks with thin fibers are resistant to lysis. Altered fibrin structure has consistently been reported in patients with several diseases complicated by thromboembolic events, including patients with acute or prior myocardial infarction, ischemic stroke, and venous thromboembolism. Relatives of patients with myocardial infarction or venous thromboembolism display similar fibrin abnormalities. Low-dose aspirin, statins, lowering of homocysteine, better diabetes control, smoking cessation, and suppression of inflammatory response increase clot permeability and susceptibility to lysis. Growing evidence indicates that abnormal fibrin properties represent a novel risk factor for arterial and venous thrombotic events, particularly of unknown etiology in young and middle-aged patients.

FXIII-A Leu34 genetic variant in premature coronary artery disease: a genotype--phenotype case control study

The FXIII-A Leu34 genetic variant increases and accelerates fibrin stabilisation; however, its association with premature coronary artery disease (CAD) and thrombotic events remains controversial. FXIII Val34Leu genotype was determined in 242 young individuals (<45 years old) who survived a myocardial infarction (MI) and 242 healthy controls matched for age and gender. We evaluated its effect on long-term clinical outcome defined as a composite of cardiovascular death, recurrent MI and urgent revascularisation. In addition, fibrin clot stiffness (elastic modulus or EM) and response to rt-PA-mediated fibrinolysis (fibrinolysis rate) were measured ex vivo using the Hemodyne analyser and confocal microscopy as surrogate endpoint. FXIII-A Leu34 genetic variant was not associated with premature CAD (adj. odds ratio 0.83 [0.49-1.4]) nor did it influence clinical outcome in patients, during a median follow-up of 6.3 (± 2.4) years. Patients produced stiffer fibrin clots (median [IQR] EM = 20.3 [14.9-28.1] vs. 12.8 [9.6-17.1] kdynes/cm²; p<0.0001) and displayed reduced response to fibrinolysis with lower fibrinolysis rate (6.7 [3.4-11.0] vs. 9.0 [5.0-16.7] sec-¹ x 10(-4); p<0.0001) than healthy controls. Carriage of factor XIII-A Leu34 led to a stepwise decrease in fibrinolysis rate with a significant gene-dose-effect in patients (7.7 [4.1-12.2] vs. 4.8 [3.0-8.5] vs. 4.3 [2.4-8.1] sec-¹ x 10(-4), for wild-type, heterozygous and homozygous, p for trend = 0.003) and a non-significant trend in controls (p = 0.01). In conclusion, FXIII-A Leu34 is a polymorphism which provides a strong resistance to fibrinolysis with a gene-dose effect, but does not relate to premature CAD or to recurrent coronary events in this study.

Arterial thrombus formation in cardiovascular disease

The pathogenesis of arterial thrombosis is complex and dynamic. Unlike venous thrombi, arterial thrombi typically form under conditions of high blood flow and are mainly composed of platelet aggregates, giving them the appearance of 'white clots'. Strong evidence suggests that arterial thrombi originate as a consequence of an injured atherosclerotic plaque, and that their formation involves the release of prothrombotic material (such as tissue factor), platelet aggregation, and platelet adhesion to the vascular wall. The initially labile platelet plaque is then stabilized by insoluble fibrin produced upon activation of the coagulation cascade. Inherited genetic factors (gene polymorphisms) and acquired predisposing conditions (such as the concentration and activity of clotting factors) can influence both the composition and the size of an arterial thrombus. Further research is needed to elucidate the functions of blood coagulation proteins and cellular elements that are critical to the pathogenesis of arterial thrombosis. This Review explains mechanisms of pathological arterial thrombus formation and discusses genetic and acquired risk factors of atherothrombosis.

An update of the mutation profile of Factor 13 A and B genes

Mutational reports over the past two decades have accumulated an immense amount of literature for inherited Factor XIII deficiency. However, the genotype and phenotype correlations for inherited Factor XIII deficiency are complicated. While many studies clearly prove a cause and effect relationship for the reported mutations, others are lacking in this regard. The F13B gene remains an elusive component as far as inherited Factor XIII deficiencies are concerned. Also, an in-depth analysis into the heterozygous state of this deficiency is also lacking. In this review we have tried to analyze and present an exhaustive amount of mutational data from the past three decades. The source of our mutational data is our website dedicated to Factor XIII deficiencies (www.F13-database.de) as well as literature search done on the Pubmed (www.ncbi.nlm.nih.gov/pubmed).

Sequence variations in the FII, FV, F13A1, FGB and PAI-1 genes are associated with differences in myocardial perfusion

AIMS

Coronary artery disease (CAD) is a significant cause of morbidity and mortality in modern societies. The association between genetic markers and CAD is still poorly understood. In this study, we evaluated the effect of five genetic variants: Factor V Leiden (FV:c.1691G>A) (rs6025), Factor II prothrombin (FII:c.20210G>A; rs1799963), plasminogen activator inhibitor 1 (PAI-1) -675(4G/5G; SERPINE1:g.4329_4330insG; rs34857375), β-fibrinogen -455G>A (FGB:c.4577G>A; rs1800790) and Factor XIII (F13A1:c.103G>T; rs5985) on myocardial perfusion.

MATERIALS & METHODS

We examined 523 patients using exercise-rest myocardial perfusion single photon emission computed tomography, where the summed stress score (SSS), summed rest score and summed difference score (SDS) indexes, were calculated. In order to examine the independent prognostic ability of genotype on SSS and SDS, multiple linear regression models were used.

RESULTS

It was found that Factor V Leiden, Factor XIII, β-fibrinogen and PAI-1 genotypes were independent prognostic predictors of SSS and SDS with Factor XIII exhibiting the strongest association. Moreover, Factor II prothrombin proved an independent prognostic predictor of SSS.

CONCLUSION

Our study provides the first evidence of an association between these polymorphisms and myocardial perfusion, suggesting that the process of coronary artery disease and also patients' prognosis, may be modified by the FV:c.1691G>A, FII:c.20210G>A, PAI-1 -675 (4G/5G), β-fibrinogen FGB:c.4577G>A and F13A1:c.103G>T genotypes.

Sensitive and selective detection of free FXIII activation peptide: a potential marker of acute thrombotic events

Coagulation factor XIII (FXIII) stabilizes fibrin fibers and is therefore a major player in the maintenance of hemostasis. FXIII is activated by thrombin resulting in cleavage and release of the FXIII activation peptide (AP-FXIII). The objective of this study was to characterize the released AP-FXIII and determine specific features that may be used for its specific detection. We analyzed the structure of bound AP-FXIII within the FXIII A-subunit and interactions of AP-FXIII by hydrogen bonds with both FXIII A-subunit monomers. We optimized our previously developed AP-FXIII ELISA by using 2 monoclonal antibodies. We determined high binding affinities between the antibodies and free AP-FXIII and demonstrated specific binding by epitope mapping analyses with surface plasmon resonance and enzyme-linked immunosorbent assay. Because the structure of free AP-FXIII had been characterized so far by molecular modeling only, we performed structural analysis by nuclear magnetic resonance. Recombinant AP-FXIII was largely flexible both in plasma and water, differing significantly from the rigid structure in the bound state. We suggest that the recognized epitope is either occluded in the noncleaved form or possesses a structure that does not allow binding to the antibodies. On the basis of our findings, we propose AP-FXIII as a possible new marker for acute thrombotic events.

Coagulation factor XIII-A Val34Leu polymorphism and the risk of coronary artery disease and myocardial infarction in a Chinese Han population

There are controversial data regarding the impact of coagulation factor XIII A subunit (FXIII-A) Val34Leu polymorphism in the pathogeneric of coronary artery disease (CAD) and myocardial infarction (MI). Assuming this genetic factor is associated with the thrombotic process, we explored the role of FXIII-A Val34Leu in CAD and MI in a Chinese Han population. We recruited 195 consecutive patients with CAD confirmed by coronary angiography as well as a group of 203 controls. Factor XIII A Val34Leu polymorphism was determined through polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis. We did not find the Leu/Leu genotype in patients with CAD or controls. No significant difference in Val34Leu gene polymorphism distribution was found between patients with CAD and the controls (P = .923). Subgroup analysis according to the history of MI showed the heterozygote Val/Leu genotype was associated with a significantly decreased risk of MI (P = .005; adjusted odds ratio [OR] = 1.75; 95% confidence interval [CI] = 1.28-2.25). Furthermore, our study displayed that the frequency of the Leu34 allele in a Chinese Han population was lower than that in Caucasian populations (2.5 vs 20.4%-28.3%). Our preliminary data indicate that the FXIII-A Leu34 allele may contribute to a protective effect against the development of MI. There is a low prevalence of the Leu34 allele in Han Chinese compared to Caucasians.

Lack of association between FXIII-Val34Leu, FVII-323 del/ins, and transforming growth factor beta1 (915G/T) gene polymorphisms and bronchopulmonary dysplasia: a single-center study

Bronchopulmonary dysplasia (BPD) is a multifactorial disease of preterm infants that is characterized by airway injury, inflammation, and parenchymal remodeling. Extravascular fibrin deposits in septae and alveoli due to the altered fibrin turnover are the pathological hallmarks of BPD that strongly indicates the importance of the imbalance in the competing activities of coagulation and fibrinolysis. Activation of the coagulation cascade leads to intraalveolar fibrin deposition in many inflammatory pulmonary disorders. Increased fibrin formation or decreased fibrinolysis may cause extravascular fibrin deposition. We evaluated the association between FXIII-Val34Leu, FVII-323 del/ins, and transforming growth factor beta1 (TGF-beta(1)) (915G/T) gene polymorphisms in patients with BPD. The study group consisted of 98 preterm infants with BPD. Ninety-four of the 192 preterm neonates were without BPD and sampled for the control group. Restriction fragment size analyses were performed by examining digested PCR products for FXIII-Val34Leu, FVII-323 del/ins, and TGF-beta(1) (915G/C) genotypes. No significant associations were found between FXIII-Val34Leu, FVII-323 del/ins, TGF-beta(1) (915G/C) gene polymorphisms and BPD phenotype in our population. Further studies with other genes are required for the identification of molecular predisposing factors for BPD that may help in the development of new treatments and hence might allow for targeting of this treatment to a "high-risk" subgroup, reducing unnecessary exposure to potentially harmful therapies.

Factor XIII deficiency

Inherited factor XIII (FXIII) deficiency is a rare bleeding disorder that can present with umbilical bleeding during the neonatal period, delayed soft tissue bruising, mucosal bleeding and life-threatening intracranial haemorrhage. FXIII deficiency has also been associated with poor wound healing and recurrent miscarriages. FXIII plays an integral role in haemostasis by catalysing the cross-linking of fibrin, platelet membrane and matrix proteins throughout thrombus formation, thus stabilizing the blood clot. The molecular basis of FXIII deficiency is characterized by a high degree of heterogeneity, which contributes to the different clinical manifestations of the disease. There have been more than 60 FXIII mutations identified in the current literature. In addition, single nucleotide polymorphisms have been described, some of which have been shown to affect FXIII activity, contributing further to the heterogeneity in patient presentation and severity of clinical symptoms. Although there is a lifelong risk of bleeding, the prognosis is excellent when current prophylactic treatment is available using cryoprecipitate or plasma-derived FXIII concentrate.

Decreased factor XIII levels in factor XIII A subunit Leu34 homozygous patients with coronary artery disease

INTRODUCTION

The effect of factor XIII A subunit (FXIII-A) Val34Leu polymorphism on the risk of coronary artery disease (CAD) has been extensively studied. In this study we investigated how FXIII-A Val34Leu genotypes influence plasma factor XIII levels in patients with coronary sclerosis (CS) and myocardial infarction (MI) and how fibrinogen level modulates this effect.

PATIENTS AND METHODS

955 consecutive patients admitted for coronary angiography were categorized according to the presence or absence of significant CS and the history of MI. The frequency of FXIII-A Val34Leu polymorphism, fibrinogen, FXIII activity and antigen levels were determined.

RESULTS AND CONCLUSIONS

CS or MI decreased FXIII levels in patients homozygous for FXIII-A Leu34 allele, but not in heterozygous or wild type patients. In the subgroup of patients with CS, but without the history of MI no significant effect was detected, which suggests that MI has a more prominent role. The specific activity of plasma FXIII was independent of FXIII-A Val34Leu genotype. FXIII and fibrinogen levels significantly correlated in CS+ and MI+ patients. In MI+ patients of Leu/Val or Leu/Leu genotypes and with fibrinogen levels in the lowest quartile, FXIII levels were lower than in the same patient groups, but with higher fibrinogen level. The low-scale continuous activation of blood coagulation in CAD patients could lead to parallel FXIII and fibrinogen consumption. As the same amount of thrombin activates more Leu34 FXIII than Val34 FXIII, increased FXIII consumption might be responsible for the decreased FXIII levels in Leu34 homozygous CAD patients.