The Study Of Angiogenesis In Cerebral Protection Induced By Limb Remote Ischemic Preconditioning In DMCAO Model In Rats

Objectives Remote ischemic preconditioning(RPC) has been confirmed as a feasible and attractive procedure for cerebroprotection in both experimental and clinical studys. However, its molecular mechaniams remain not fully understood. Angiogenesis, the growth of blood vessels from the existing vasculature, is an important natural process in the body used for healing and reproduction. The aim of this study was to test whether RPC has an effect on angiogenesis and the expression pattern of angiogenic molecules, through which RPC exert its protective function.Methods Cerebral ischemia was generated by a permanent occlusion of the left distal middle cerebral artery (dMCAO) combined with a 30min occlusion of the bilateral common carotid arteries (CCA) in male rats. Limb preconditioning was generated by 15min occlusion followed with the same period of reperfusion of the left hind femoral artery, and repeated for three cycles. Microvessel density (using anti-CD31antibody) of ischemic penumbra was counted, expression of VEGF/VEGFR-2 system, Ang/Tie-2 system and HIF-1alpha was measured semi-quantitatively by means of immunohistochemistry and western blotting.Results Microvessel density in ischemic penumbra was significantly increased in RPC group than in ischemic control group from 1 day to 2 weeks after dMCAO, both groups peaking at 7 days. Level of VEGFR-2 and Tie-2 was upregulated more remarkably in RPC group than in ischemic control group (compared with baseline level). Chronological expression of VEGFR-2 in both groups was similar with that of microvessel density. For Tie-2, upregulation was detected from 2 days to 14 days after ischemia onset, ischemic control group peaked at 7 days and preconditioning group at 7 days and sustained to 14 days. For secretory factors, expression of VEGF and Ang-2 was more abundant in RPC group than in control group at 2 days and 7 days in ischemic penumbra after operation. Just the opposite, level of Ang-1 was lower in RPC group.Conclusions RPC enhanced process of angiogenesis and changed the expression pattern of angiogenic molecules after cerebral ischemia in rats. This may be the key molecular mechanism of neuroprotection exerted by RPC.