CD34 positive cells as endothelial progenitor cells in biology and medicine.

CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34 cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34 cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34 cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34 cell therapy in various diseases. However, the clinical application of CD34 cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34 cells as well as the preclinical/clinical details of CD34 cell therapy for regenerative medicine.