Correlation of CD34+ cells with tissue angiogenesis after traumatic brain injury in a rat model.

Increasing evidence suggests that circulating endothelial progenitor cells, which are a subpopulation of hematopoietic progenitor CD34(+) cells, play a critical role in neovascularization and tissue repair. We have tested the hypothesis that traumatic brain injury (TBI) could mobilize CD34(+) cells to peripheral blood and brain tissue, a process critical for vascular repair, in a rat model of TBI. Male Wistar rats were subjected to controlled fluid percussion. Blood and brain tissue were collected before and after TBI to measure the levels of CD34(+) cells in peripheral blood and to detect their accumulation in the damaged cerebral tissue. Compared with surgery controls, CD34(+) cells significantly increased in the peripheral blood and accumulated in the brain tissue of TBI rats. Immunohistochemistry detected new vessels with incomplete CD34(+) endothelial-like cell lining and an increased number of microvessels in the injured and surrounding tissue. The results demonstrate a close correlation between an increase in circulating CD34(+) cells in response to traumatic injury and angiogenesis in TBI rat brain. They also suggest that transplantation of CD34(+) cells or augmentation of endogenous CD34(+) cells may be a novel therapeutic approach for patients with TBI.