CD133 expressing pericytes and relationship to SDF-1 and CXCR4 in spinal cord injury

Compression injury to the spinal cord (SC) results in vascular changes affecting the severity of the primary damage of the spinal cord. The recruitment of bone marrow (BM)-derived cells contribute to revascularization and tissue regeneration in a wide range of ischemic pathologies. Involvement of these cells in the vascular repair process has been investigated in an animal model of spinal cord injury (SCI). Temporal gene and protein expression of the BM-derived stem cell markers CD133 and CD34, of the mobilization factor SDF-1 and its receptor CXCR4 were determined following SC compression injury in rats. CD133 was expressed in uninjured tissue by cells surrounding arterioles identified as pericytes by co-expression of alpha-SMA. These cells mostly disappeared 2 days after injury but repopulated the tissue after 2 weeks. CD34 was expressed by endothelial cells and CD11b+ macrophages/microglia invading the injured tissue as observed 2 weeks following injury. SDF-1 was induced in reactive astrocytes and endothelial cells not until 2 weeks post-SCI. Comparison of the variation between CD34, CD133, CXCR4, and SDF-1 revealed a corresponding trend of CD133 with the SDF-1 expression. This study showed that resident microvascular CD133+ pericytes with presumptive stem cell potential are sensitive to SCI. Their decline following SCI and the delayed induction of SDF-1 may contribute to vessel destabilisation and inefficient revascularization. In addition, none of the analyzed markers could be assigned clearly to BM-derived cells. Together, our findings suggest that effective recruitment of pericytes may serve as a therapeutic option to improve microcirculation after SCI.