Mobilization, endothelial differentiation and functional capacity of endothelial progenitor cells after ischemic stroke

Endothelial progenitor cells (EPCs) have introduced new possibilities for cell-based vasculogenesis treatment after stroke. In this study we quantified circulating levels of EPCs in stroke patients and in healthy controls, and evaluated the potential of EPCs to induce vasculogenesis in vitro. Blood was drawn from tPA-treated stroke patients and control subjects, and the circulating EPCs levels in each group were quantified by flow cytometry and cell culture assays. Immunophenotyping was performed using multiple markers (UEA-lectin, CD133, vWF and KDR) and tubulogenic function was assessed with the Matrigel® assay. The produced angiogenic factors were quantified by multiple ELISA and RT-PCR. Fluorescence-activated cell sorting (FACS) revealed higher levels of circulating CD133+/CD34+/KDR+/CD45+ cells in the acute strokes as compared to the control subjects (p = 0.02). On the other hand, more EPCs grew in cell culture from subacute strokes (p = 0.016) than from controls. The endothelial and progenitor lineages of the EPCs were confirmed by immunophenotyping. Interestingly, the appearance of outgrowth EPCs (OECs) correlated positively to stroke severity (p = 0.013). Finally, greater capacity to induce vasculogenesis in vitro was found in EPCs from subacute strokes (p = 0.03), which we attribute to a higher expression and secretion of angiogenic factors. Our results suggest an early EPC mobilization but an enhanced angiogenic function in the subacute phase of stroke. Nonetheless, development of cell-based therapy for stroke will require further studies to identify those EPCs with the greatest therapeutic potential.