Effects of bone mesenchymal stem cells (BMSCs) on the rat pial microvascular remodeling after transient middle cerebral artery occlusion and different reperfusion times

Transplantation of bone mesenchymal stem cells (BMSCs) represent a potential therapy for ischemic stroke, we sought to evaluate the long-term effects of these cells treatment on rat pial microcirculation after middle cerebral artery occlusion (MCAO). Male rats were subjected to 2-hours MCAO followed by an infusion of 1 x 106 BMSCs or phosphate-buffered saline into internal carotid artery. Pial microcirculation was observed through a closed cranial window at different reperfusion time (7, 14 and 28 days) by fluorescence microscopy. Geometric characteristics of pial arteriolar networks, permeability increase, leukocyte adhesion, perfused capillary density were analyzed. The expression of the most important proteins in the process of angiogenesis was evaluated by western blot analysis. Finally, we performed green fluorescent protein (GFP)-BMSCs to transplanted to follow their distribution on infarcted area. The post-ischemic penumbra induced by MCAO is a site of intense microvascular reorganization, characterized by new vessel connections resulting in several anastomotic arterioles. The intracarotid administration of bone mesenchymal stem cells up to 28 days post middle cerebral artery occlusion induced an accelerated pial vascular remodeling. These arcades were likely vessels sprouting from preexistent arterioles localized in the penumbra area, able to place on the ischemic core, accompanied by increased expression of vascular endothelial growth factor and endothelial nitric oxide synthase. GFP-BMSCs showed the distribution and organization in infarcted area up to 28 days of reperfusion. Pial vascular remodeling after MCAO mainly involves arteriolar networks; the graft of bone mesenchymal stem cells accelerates this processes through angiogenic mechanisms.