Abstract
Cells expressing NG2 chondroitin sulfate proteoglycan (NG2) in the brain have been considered to be oligodendrocyte progenitor cells. We found, however, most cells expressing NG2 also expressed Iba1, a microglia/macrophage marker, in the core of ischemic brain lesions of rats that were subjected to transient middle cerebral artery occlusion (MCAO). The cells expressing both Iba1 and NG2 (Brain Iba1+/NG2+ Cells; BINCs) displayed macrophage-like morphology and had phagocytic activity. BINCs were highly proliferative and expressed another OPC marker platelet-derived growth factor α receptor (PDGFαR). BINCs isolated from the core of MCAO lesions proliferated in response to PDGF-AA, a ligand for PDGFαR. To label dividing cells in the ischemic core of the MCAO lesion at 2 days post-reperfusion (2 dpr), 5-bromo-2-deoxyuridine (BrdU) was administered to the ischemic rats. Then, about 80% of BrdU-labeled cells were BINCs. Based on this result, BINCs were killed by administrating 5-fluorouracil (5FU) to rats at 2 dpr. The administration of 5FU increased apparently infarct volume that accompanied marked decrease of BINCs in number, and nearly 60% of rats died by 14 dpr. These results suggest that BINCs played favorable roles in ischemic lesions to reduce the infarct volumes. Isolated BINCs can transdifferentiate into cells with neuroectodermal phenotypes and this multipotentiality might be involved in the regeneration of the ischemic brain. [J Physiol Sci. 2007;57 Suppl:S118]
