PB0846 - Influence of gut commensals on murine deep vein thrombosis and platelet function

Background: The commensal microbiota, a persistent environmental challenge, influences vascular inflammation and atherosclerosis development. While the gut microbiota's role in arterial thrombosis is recognized in mouse models and human studies, its influence on venous thrombosis, particularly deep vein thrombosis (DVT), remains largely unexplored. DVT, initiated by endothelial activation, is dominated by myeloid cell adhesion to the activated endothelium, while platelets act as mediators for further neutrophil recruitment. The vascular endothelium can be activated by gut barrier defects, which result in an increase of bacterial products in the circulation, triggering inflammatory cell adhesion.

Aims: Here, we used gnotobiotics combined with a standardized thrombosis mouse model, the inferior vena cava (IVC) stenosis, to study the microbiota’s effect on venous thrombosis in vivo. Furthermore, we investigated the micriobiota’s impact in blood and platelet functional assays ex vivo.

Methods: We applied the IVC model, inducing a 48-hour blood flow restriction, to determine thrombus weights in germ-free (GF) and conventionally raised (CONV-R) mice. The microbiota's impact on blood coagulation was assessed by thromboelastometry. The influence of gut commensals on platelet function was studied ex vivo using aggregometry, flow cytometry, and calibrated automated thrombography to monitor thrombin generation.

Results: Of note, the absence of microbiota in the germ-free mouse model did not affect thrombus formation in the stenosed IVC under the applied conditions. Thrombus size was unchanged in GF mice as compared to CONV-R counterparts. This was verified ex vivo by unaltered blood clotting However, GF mice showed decreased thrombin induced aggregation capacities and reduced P-selectin exposure following activation with the GPVI agonist convulxin. Interestingly, tissue factor-induced thrombin generation was also slightly reduced in platelets of GF mice.

Conclusion(s): The microbiota does not influence venous thrombosis in a 48h murine IVC stenosis model. Although microbiota is an effector of platelet function, thrombus weight was found unaltered during in vivo IVC.