CXCR4, a Key Modulator of Vascular Progenitor Cells

Abstract

A growing body of evidence suggests that circulating progenitors participate in vascular healing and remodeling under physiological and pathological conditions (Figure).1–3 It is believed that the majority of vascular progenitor cells originate from the bone marrow. Stem cells within the bone marrow usually exist in a quiescent state. Specific signals stimulate the stem cells to differentiate and move to systemic circulation (Mobilization). Progenitors are recruited and stay at the site of vascular repair or neovascularization (Homing), where they differentiate into endothelial-like cells or smooth muscle–like cells (Differentiation) and proliferate (Proliferation). The molecular processes leading to their mobilization from the bone marrow and homing to the sites of vascular remodeling or neovascularization are not fully understood.4,5 In the current issue of Arteriosclerosis, Thrombosis, and Vascular Biology , two articles6,7 provide new insights into the essential role of CXCR4, the receptor for stromal cell–derived factor-1 (SDF-1) for the mobilization and the recruitment of bone marrow (BM)-derived cells. CXCR4 is notably expressed on hematopoietic stem cells and has previously been shown to play a key role in their homing and mobilization.8 Activation of this G protein–coupled 7-transmembrane receptor induces adhesion molecules on the hematopoietic progenitor/stem cell surface thereby enhancing their homing capacities9 and regulating their proliferation.10 Contribution of bone marrow–derived cells to neointima formation and angiogenesis. On severe vascular injury, bone marrow–derived cells are …