Abstract 121: Acetylsalicylic Acid Accelerates Murine Stasis Venous Thrombus Resolution, Independent Of Sex

Background: The lack of a stasis venous thrombosis (VT) model in female mice has limited investigation on sex differences of anti-VT therapies, such as acetylsalicylic acid (ASA), which appears efficacious in preventing recurrent VT. Here we (i) develop a new extended stasis VT model; and (ii) examine the effects of ASA on stasis VT resolution in female and male mice using serial intravital microscopy. Method: To extend stasis thrombus persistence, femoral vein was ligated followed by second ligation of saphenous vein (Fig. A), after 7 days of either PBS/ASA (3mg/kg, n=5-6) pre-treatment. Following FITC-dextran injection (10 mg/kg), FITC light irradiation (475/35nm, 20x) for three minutes across three illumination fields generated stasis VT. Dylight649-GPIbβ agent was injected (100ug/kg, ex 630nm) to observe platelets. At T30’, fibrin targeting agent-FTP11-CyAm7 (150nmol/kg, ex 750 nm) was injected. Serial epifluorescence IVM images were acquired (90i, NIS Elements software, Nikon). Results: Double ligation (DL) thrombus was significantly larger than single ligation (SL) and remained so through 24h (Fig B-G) and 48h (data not shown). Corresponding sections of thrombus showed a persistent core consisting platelets and fibrin (Fig. H-J). In DL, females developed reproducible stasis VT burden and resolution profiles as in males (Fig. K). ASA pre-treatment resulted in reduced thrombus (T0’), and accelerated resolution in both sexes (Fig. L-P). ASA inhibited platelet recruitment to thrombi within T30’, consistent with its known anti-platelet effect. Also, ASA inhibited fibrinogenesis, suggestive of an impaired platelet-fibrin interface. Conclusion: Here we establish a new extended stasis VT model applicable to both female and male mice. This model is amenable to study vein wall fibrosis-critical aspect of post-thrombotic syndrome. Furthermore, ASA inhibits thrombus formation and accelerates thrombus resolution in a sex-independent manner.