Abstract 17199: Platelet ROCK2 is an Important Mediator of Thrombotic Stroke
Background: The activation of platelets is the final common pathway for most ischemic strokes. However, the signaling pathways that lead to platelet activation are not well understood. The Rho-associated coiled-coil forming kinases (ROCKs) are important mediators of the actin cytoskeleton. Because changes in the actin cytoskeleton underlie platelet activation and aggregation, we hypothesize that ROCKs in platelets may play an important role in thrombus-mediated ischemic stroke.
Methods and Results: Platelets from global ROCK2-deficient (ROCK2-/-) mice showed decreased thrombin-induced pseudopodia formation, collagen adhesion, and homo- and heterotypic aggregation compared with platelets from wild-type (WT) mice. To determine the role of platelet ROCK2 in thrombosis-mediated ischemic stroke, we generated a mouse strain with platelet-specific ROCK2 deficiency (ROCK2Plt-/-) using conditional ROCK2flox/flox mice and platelet-specific PF4-Cre mice. ROCK2Plt-/- mice were born at expected Mendelian ratios and did not show any obvious developmental or phenotypic abnormalities. One day before ischemic onset, arterial blood was withdrawn from donor mice (WT or ROCK2Plt-/- mice), into PE-50 tubing, stored at room temperature for 2 hrs, and then kept at 4 °C for 22 hrs. Middle cerebral artery (MCA) occlusion was induced by injection of the coagulated blood into recipient WT mice. Laser Doppler flowmetry was used to confirm successful MCA occlusion. Following clot injection, an embolus of varying size was found in the proximal MCA of all mice at 24 hrs. Compared to WT→WT mice, ROCK2Plt-/-→WT exhibited greater improvement in relative cerebral blood flow (rCBF) (19% vs. 92% reduction, p=0.0026). This correlated with decreased cerebral infarct size (67.6 ± 18.9 mm3 vs. 126.3 ± 17.0 mm3, p<0.05, n=6-9) and improved neurological deficit score (2.3 ± 0.4 vs. 3.5 ± 0.5, p=0.037, n=6-9).
Conclusion: These finding indicate that ROCK2 in platelets is critical for thrombus formation and in mediating MCA occlusion in the clot-embolic model of stroke. These results suggest that inhibition of platelet ROCK2 may have therapeutic benefits in ischemic stroke.
- © 2011 by American Heart Association, Inc.