Peripheral blood of adults contains low levels of a subtype of progenitor cells that have the capacity to differentiate into mature endothelial cells and hence they are termed as EPCs (Endothelial Progenitor Cells). These cells have the potential to perform neo-vascularization and re-endothelialization of the injured tissue. Bone marrow of adults contains a reservoir of these progenitor cells which can migrate to the peripheral circulation on receiving the appropriate stimulus and thus perform the necessary functions apart from differentiating to mature endothelial cells. Most of the literature states that isolation and selection of EPCs can be performed from different sources by adherence culture and magnetic microbeads. EPCs are normally characterized by the presence of three-antigen combination of CD34, CD133 and VEGFR2. However, when migrating to the circulation i.e. during differentiation, these progenitors start to lose CD133 and begin to express endothelial specific markers like CD31, VE-cadherin and vWF. In context of therapeutic application of these cells, there are few clinical trials which have started to employ EPCs for treating various ischemic diseases though there has been inconsistency in the clinical outcome. Hence, further and deeper understanding in the field of EPCs can bring about a general consensus on their specific identity along with their mechanisms of homing and differentiation which are largely unclear at present. This review summarizes the role of EPCs in some of the major diseases, their isolation, characterization and functionality assays, mechanisms of homing and differentiation along with their circulating levels in vivo under certain conditions and factors.
Author(s): Prathibha Shetty, Kinjal Shah, and Chandra Viswanathan