Abstract 350: Activation of Platelet CLEC-2 in Hematoma Expansion After Intracerebral Hemorrhage: Finding an Effective Dose

Abstract

Intracerebral hemorrhage (ICH) is the least treatable and one of the most disabling stroke subtypes, with both the primary and secondary brain injuries mainly due to hematoma expansion (HE) within the first few hours, followed by an inflammatory and oxidative injury. Almost all ICH patients experience some degree of expansion, and ICH volume can be an independent determinant of mortality and functional outcome. Previous studies found that reduced platelet activity is associated with early ICH growth and worse functional outcomes. The platelet C-type lectin-like receptor 2 (CLEC-2) elicits robust platelet activation upon stimulation. Thus, we hypothesized that activation of CLEC-2 would result in activation and aggregation of platelets, reducing HE, and improving functional outcomes after ICH. We administered two CLEC-2 agonists (Fucoidan and the endogenous ligand Podoplanin) at varying doses after murine ICH and measured hemorrhage volume, brain water content, and behavior. We also collected blood from podoplanin-treated mice and conducted hematologic tests. We further tested Rhodocytin, a known CLEC-2 activator, for whole blood clotting times, platelet functions, and soluble fibrin in human blood samples. We found that treatment with Fucoidan did not reduce hemorrhage volume or brain water content and had no effect on neurological function, compared to vehicle. Further, Podoplanin treatment showed a tendency to reduce brain water content but did not affect hematoma volume or behavior. Our in vitro studies showed lower fibrinogen levels with podoplanin treatment, compared to sham and vehicle, but no effect on partial thromboplastin time, prothrombin time, or INR. At higher doses, Rhodocytin resulted in immediate clotting, while at lower doses, it significantly increased soluble fibrin, consistent with initiation of clotting seen in the higher doses. In conclusion, our findings indicate that activation of CLEC-2 at the doses tested does not reduce ICH volume or improve outcomes, but did affect hemostatic parameters. Thus, the agonists may produce favorable outcomes with a different dosing regimen. Further studies are needed to confirm the mechanism by which CLEC-2 is acting in ICH, effective doses, and the effect of altered bleeding parameters.