Von Willebrand Factor-Dependent Inflammatory Responses in Mouse Septic Model By Cecal Ligation and Puncture

Sepsis is a serious inflammatory response syndrome, in which systemic activation of both inflammatory and coagulation pathways are provoked by severe microbial infection. In addition to the known hemostatic functions, von Willebrand factor (VWF) is recently assumed to participate in a cross-talk between inflammation and thrombosis. Indeed, recent mouse model studies demonstrated that proper functional regulation of VWF-dependent inflammatory responses by ADAMTS13 considerably improved the disease progression of brain stroke or myocardial infarction. However, little is known about the detailed mechanisms or relevant role of VWF functions in inflammation. We therefore studied the physiologic relevance of VWF-dependent inflammatory responses in a mouse model of experimental sepsis by cecal ligation and puncture (CLP). The mouse CLP was performed according to the established standard protocol (Rittirsch D, et al., Nat Protoc, 2009). Briefly, mouse cecum was ligated distal to the ileocecal valve under laparotomy, punctured with 18 gauge needle and gently pressed until a small drop of stool appeared. The cecum was returned to the peritoneal cavity and 200 μL of saline was injected into the cavity to avoid dehydration before body wall and skin incision were closed with a 4-0 Sofsilk. We compared 17 wild-type (WT) and 17 VWF-gene deleted (knock-out; KO) mice (from The Jackson Laboratory, Bar Harbor, ME), all of which were 10-12 weeks of age, healthy and fertile. Excess blood loss was not observed in all (WT or KO) mice during the CLP operation. Kaplan-Meier analysis revealed the significantly (p < 0.05) lower survival rate of KO mice than that of WT (KO; 23.5% vs. WT; 58.8% at the Day 7 of CLP). The impaired survival rate of KO mice was restored by the bolus administration of human VWF (n=21, 2.5 U/mouse) to an extent comparable to that of WT. Peripheral blood analysis of KO mice at 24 hours after CLP showed the severe leukocytopenia with sharp decrease of neutrophils in blood, as compared to WT. In addition, formation of walled-off abscess was confirmed at the peri-cecal space in all the WT and KO mice alive even at the Day 7 of CLP, while such focal abscess formation was not found in mice died before the Day 3 of CLP. Thus, our results altogether indicate that VWF could play a role on the recruitment or accumulation of neutrophils for microbial killing at the local inflammatory focus. VWF-mediated platelet aggregate formation in peripheral capillary vessels then could shut down the local microcirculation, thereby blocking systemic microbial expansion as a crucial biological defense mechanism.