Endothelial Progenitor Cells: Properties, Function, and Response to Toxicological Stimuli

The repair and regeneration of adult tissues is accomplished through the existence and function of stem or progenitor cell populations. With regards to vascular repair, this is accomplished through the use of heterogeneous populations of proangiogenic cells, often called the endothelial progenitor cells (EPCs). In response to hypoxic or inflammatory signals, EPCs are mobilized from storage niches such as the bone marrow, home to site of vascular damage and participate in repair through terminal differentiation or paracrine effects. While the existence of these endothelial reparative cells has been recognized for almost 20 years, an accurate phenotypic description of these cells still remains controversial and complex analytical strategies are required for their identification and functional analysis. Multiple animal and human studies have demonstrated the physiological importance of EPCs, and evidence suggests a paucity of these cells or their dysfunction is correlated with poor vascular health and an increased risk of developing or exacerbating cardiovascular disease. Moreover, the levels and functionality of these cells are particularly sensitive to toxicological exposures and external influences, defining a mechanistic connection between such stimuli and resulting pathology.