PTPRC and Stroke: Given that most studies of EPC-therapy are conducted with ex vivo expanded EPCs for cardiac and post-stroke pre-clinical and clinical studies [1], [5], [12], our data showing that freshly isolated juvenile cd45- [cd34+/kdr+]EPCs act as juvenile protective factors for ischemic-hemorrhagic stroke are concordant with studies reporting hematopoietic stem cell roles rather than endothelial repair roles for ex vivo culture-expanded cd45+ EPCs or colony forming cells [17]–[19].