Impaired clot retraction in factor XIII A subunit–deficient mice

Abstract

Factor XIII (FXIII) is a plasma transglutaminase that cross-links fibrin monomers, ␣ 2 -plasmin inhibitor, and so forth. Congenital FXIII deficiency causes lifelong bleeding symptoms. To understand the molecular pathology of FXIII deficiency in vivo, its knockout mice have been functionally analyzed. Because prolonged bleeding times, a sign of defective/abnormal primary hemostasis, were commonly observed in 2 separate lines of FXIII A subunit (FXIII-A) knockout mice, a possible role or roles of FXIII in platelet-related function was investigated in the present study. Although platelet aggregation induced by adenosine diphosphate or collagen was normal, clot retraction (CR) was lost in the platelet-rich plasma (PRP) of FXIII-A knockout mice. IntroductionCoagulation factor XIII (FXIII) is a pro-enzyme of plasma transglutaminase (TGase) consisting of 2 enzymatic A subunits (FXIII-A) and 2 noncatalytic B subunits, and plays a critical role in the generation of a stable hemostatic plug. 1-3 FXIII catalyzes intermolecular cross-linking reactions between fibrin monomers, ␣ 2 -plasmin inhibitor, fibronectin, etc. These reactions increase the mechanical strength of the fibrin clot and its resistance to proteolytic degradation, and enhance the assembly of the extracellular matrix.Congenital FXIII deficiency is a rare autosomal recessive disorder, the cases of most of which are caused by defects in the FXIII-A gene. 3 A lifelong bleeding tendency, abnormal wound healing, and recurrent spontaneous miscarriage are common symptoms of FXIII deficiency. 1,4 FXIII-A exists extracellularly in plasma as well as intracellularly as a cytosolic protein in megakaryocytes/platelets and monocytes/macrophages, although the function(s) of intracellular FXIII-A remain(s) unknown. 5,6 In particular, platelets cause clot retraction (CR) by retracting extended filopodia along fibrin strands. 7 There have been conflicting reports about the effects of FXIII deficiency on CR; investigators reported that the absence of FXIII abolished, 7-9 did not affect, 10,11 or rather enhanced 12 CR in patients with congenital FXIII deficiency. However, platelet aggregation induced by various agents is uniformly normal in patients with congenital FXIII deficiency. 8,9,13,14 To understand the precise molecular pathology of FXIII deficiency in vivo, FXIII-A knockout (KO) mice have been analyzed. FXIII-A KO mice demonstrated a severe bleeding tendency. 15 We also reported that FXIII-A KO mice developed severe uterine bleeding, resulting in spontaneous miscarriage in females, and male-specific intrathoracic hemorrhage as well as excessive cardiac fibrosis. 16,17 Because bleeding times in FXIII-A KO mice were longer than in wild-type, 15,18 we hypothesized that FXIII-A KO mice might have a defective platelet-related function(s). Accordingly, we have explored the contribution of FXIII to the process of CR in the present study. Methods AnimalWild-type C57BL/6J mice were obtained from Japan SLC Inc. Genetargeted mice of FXIII-A were generated as previously reported, ...

Factor XIII improves platelet adhesion to fibrinogen by protein disulfide isomerase-mediated activity

“…By contrast, Jayo et al [9] and Kasahara et al [7] reported that monodansylcadaverine and cystamine, competitive donors for transglutaminase, inhibited FXIII-mediated adhesion. The reason for the discrepancy from our study is not clear.…”

“…The involvement of FXIII transglutaminase activity in platelet spreading was suggested by previous findings that monodansylcadaverine, in the absence of added FXIII, diminished filopodia formation of normal platelets on fibrinogen [9] and that clot retraction in mice was inhibited by the FXIII transglutaminase inhibitor, cystamine [7]. Given our earlier finding that FXIIIA has PDI activity which is independent of its transglutaminase activity [10], we examined the relative roles of the two activities in platelet adhesion to fibrinogen.…”

“…Besides its role in hemostasis, FXIII accelerates wound healing [2], probably by its pro-angiogenic effects [3] as well as by stimulation of monocytes and fibroblasts [4]. Several new lines of evidence point to the involvement of FXIII in platelet function as well [5][6][7][8]. FXIII subunit A (FXIIIA) was detected on thrombin-receptor-activated platelets [5], and platelets were found to adhere to FXIII-covered surface [6]; this interaction depended on the intact fibrinogen binding to integrin αIIbβ3 [5,6].…”

“…FXIII subunit A (FXIIIA) was detected on thrombin-receptor-activated platelets [5], and platelets were found to adhere to FXIII-covered surface [6]; this interaction depended on the intact fibrinogen binding to integrin αIIbβ3 [5,6]. Accordingly, no clot retraction was noted in FXIIIA knock-out mice [7], and patients with FXIII deficiency, a rare hereditary life-long bleeding disorder [8], showed reduced fibrinogen binding to thrombin-stimulated platelets and reduced platelet adhesion to fibrinogen-covered surface [9].…”

“…FXIII subunit A (FXIIIA) was detected on thrombin-receptor-activated platelets [5], and platelets were found to adhere to FXIII-covered surface [6]; this interaction depended on the intact fibrinogen binding to integrin αIIbβ3 [5,6]. Accordingly, no clot retraction was noted in FXIIIA knock-out mice [7], and patients with FXIII deficiency, a rare hereditary life-long bleeding disorder [8], showed reduced fibrinogen binding to thrombin-stimulated platelets and reduced platelet adhesion to fibrinogen-covered surface [9].We recently reported that FXIIIA has protein disulfide isomerase (PDI) activity, independent of its transglutaminase activity [10]. Cellsurface-localized, membrane-bound PDI is essential for sustaining the binding of fibrinogen, fibronectin, and collagen to platelet integrins αIIbβ3, α5β1, and α2β1, respectively [11,12], thereby regulating platelet adhesion [11,12] and aggregation [13].…”