A novel population of α-smooth muscle actin-positive cells activated in a rat model of stroke: an analysis of the spatio-temporal distribution in response to ischemia

In a rat model of stroke, the spatio-temporal distribution of alpha-smooth muscle actin-positive, (alpha SMA+) cells was investigated in the infarcted hemisphere (ipsilateral) and compared with the contralateral hemisphere. At day 3 postischemia, alpha SMA+ cells were concentrated in two main loci within the ipsilateral hemisphere (Area A) in the medial corpus callosum and (Area B) midway through the striatum adjacent to the lateral ventricle. By day 7 and further by day 14, fewer alpha SMA+ cells remained in Areas A and B but a steady increase in the pen-infarct was observed. alpha SMA+ cells also expressed glial acidic fibrillary protein [GFAP: alpha SMA+/GFAP+ (29%); alpha SMA+/GFAP- (71%) phenotypes] and feline leukemia virus C receptor 2 (FLVCR2), but not ED1(microglia) and established markers of pericytes normally located in vascular wall. alpha SMA+ cells were also located close to the subventricular zones (SVZ) adjacent to Areas A and B. In conclusion, alpha SMA+ cells have been identified in a spatial and temporal sequence from the SVZ, at intermediate loci and in the vicinity of the pen-infarct. It is hypothesized that novel populations of alpha SMA+ precursors of pericytes are born on the SVZ, migrate into the pen-infarct region and are incorporated into new vessels of the pen-infarct regions. Journal of Cerebral Blood Flow & Metabolism (2012) 32, 2055-2065; doi:10.1038/jcbfm.2012.107; published online 18 July 2012