title: Plasma fibronectin depletion enhances platelet aggregation and thrombus formation in mice lacking fibrinogen and von Willebrand factor.
abstract: We previously showed that platelet aggregation and thrombus formation occurred in mice lacking both fibrinogen (Fg) and von Willebrand factor (VWF) and that plasma fibronectin (pFn) promoted thrombus growth and stability in injured arterioles in wild-type mice. To examine whether pFn is required for Fg/VWF-independent thrombosis, we generated Fg/VWF/conditional pFn triple-deficient (TKO; Cre(+), Fn(flox/flox), Fg/VWF(-/-)) mice and littermate control (Cre(-), Fn(flox/flox), Fg/VWF(-/-)) mice. Surprisingly, TKO platelet aggregation was not abolished, but instead was enhanced in both heparinized platelet-rich plasma and gel-filtered platelets. This enhancement was diminished when TKO platelets were aggregated in pFn-positive control platelet-poor plasma (PPP), whereas aggregation was enhanced when control platelets were aggregated in pFn-depleted TKO PPP. The TKO platelet aggregation can be completely inhibited by our newly developed mouse anti-mouse beta(3) integrin antibodies but was not affected by anti-mouse GPIbalpha antibodies. Enhanced platelet aggregation was also observed when heparinized TKO blood was perfused in collagen-coated perfusion chambers. Using intravital microscopy, we further showed that thrombogenesis in TKO mice was enhanced in both FeCl(3)-injured mesenteric arterioles and laser-injured cremaster arterioles. Our data indicate that pFn is not essential for Fg/VWF-independent thrombosis and that soluble pFn is probably an important inhibitory factor for platelet aggregation.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Adili
authors.initials: A
authors.lastname: Reheman
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Guangheng
authors.initials: G
authors.lastname: Zhu
authors.forename: Wuxun
authors.initials: W
authors.lastname: Jin
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Spring
authors.forename: Xufang
authors.initials: X
authors.lastname: Bai
authors.forename: Peter L
authors.initials: PL
authors.lastname: Gross
authors.forename: John
authors.initials: J
authors.lastname: Freedman
authors.forename: Heyu
authors.initials: H
authors.lastname: Ni
mesh_terms: D000818:Animals; D005340:Fibrinogen / Q000235:genetics* / Q000378:metabolism; D005353:Fibronectins / Q000097:blood* / Q000235:genetics*; D066298:In Vitro Techniques; D019426:Integrases / Q000235:genetics; D008638:Mesenteric Arteries / Q000293:injuries; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000098:blood supply; D010973:Platelet Adhesiveness / Q000502:physiology; D010974:Platelet Aggregation / Q000502:physiology*; D010976:Platelet Count; D012995:Solubility; D013927:Thrombosis / Q000378:metabolism* / Q000503:physiopathology; D014841:von Willebrand Factor / Q000235:genetics* / Q000378:metabolism
chemical_list: D005353:Fibronectins; D014841:von Willebrand Factor; D005340:Fibrinogen; C045073:Cre recombinase; D019426:Integrases