Abstract 648: Divergent Roles For Endothelial Cell Marcks In Endothelial Cell Regeneration And Signaling After Arterial Injury And Ischemia

Abstract

Cardiovascular interventions cause endothelial injury and trigger re-establishment of intact endothelium. After ischemia, endothelial signaling is essential for capillary angiogenesis as well as flow-mediated collateral artery enlargement to restore perfusion. We studied the role of the signaling protein MARCKS (myristoylated alanine-rich C kinase substrate) in the endothelial response to injury and ischemia-induced angiogenesis. Methods: Targeted deletion of MARCKS in endothelial cells was done with Cadherin 5-driven Cre/Lox recombination and confirmed with immunohistochemistry. All controls were Cre(-) littermates. Re-endothelialization after femoral artery wire injury was measured by arterial area quantitation after Evan’s Blue exclusion. After femoral artery ligation, limb blood flow was determined by serial laser Doppler scanning, and angiogenesis by counting CD31-positive cells in the gastrocnemius muscle on day 28. Results: Endothelial cell-specific deletion of MARCKS was confirmed in Cre (+) animals. Deletion of MARCKS did not affect endothelial regeneration on post operative day 6 after denuding femoral wire injury (68.2% versus 68.7% recovery, n=5-6, p>.05). Ischemia-induced capillary angiogenesis was not affected by deletion of MARCKS (Capillary Count, Cre(+): 602 versus Cre(-): 511, n=6, p>.05), however animals lacking endothelial MARCKS had worsened limb perfusion on days 1, 3, 7 and 21 after ischemia (ABI Range Cre(+) versus Cre(-): 0.04-0.22 versus 0.07-0.41, respectively, n=6-9, p<.05). Conclusions: These studies demonstrate distinct and divergent roles for MARCKS in the endothelial cell response to injury and ischemia. MARCKS is not essential for endothelial regeneration after denuding large vessel injury, or for capillary angiogenesis induced by ischemia. Surprisingly, endothelial MARCKS appears to be a novel endogenous promotor of ischemia-induced limb revascularization. This suggests that endothelial cell MARCKS promotes flow-mediated endothelial cell signaling essential for ischemia-induced arterial enlargement. MARCKS activity could be a possible therapeutic target to enhance collateral artery formation in limb ischemia.