Mobilization of endothelial progenitor cells into the circulation in burned patients

Background: Bone marrow-derived endothelial progenitor cells (EPCs) have been detected in the peripheral blood of patients following thermal injury. EPCs migrate to sites of active neovascularization in response to mediators released after trauma, contributing to wound healing. The aim was to characterize levels and kinetics of EPCs in burned patients, then relate these to key mobilizing factors, vascular endothelial growth factor (VEGF) and the chemokine (C-X-C motif) ligand 12 (CXCL 12), and compare them with those in healthy subjects. Methods: The study included 19 adult patients with superficial or full-thickness bums and 50 blood donor volunteer controls. EPCs, identified by cell surface markers CD45(dim/-), CD133(+), CD144(+) and VEGF receptor 2, were quantified by four-colour flow cytometry. Plasma VEGF and CXCL12 were measured using enzyme-linked immunosorbent assay. Results: Burned patients showed a rapid rise in EPC levels within 24 h, a ninefold increase compared with controls, returning to basal levels by 72 h. Body surface area burned correlated strongly with the degree of mobilization. EPC levels correlated significantly with rises in plasma VEGF and CXCL12. Conclusion: Thermal injury induced a rapid rise in EPCs that was proportional to the extent of the burn and significantly correlated with levels of angiogenic cytokines. Such cytokines may be used to stimulate EPCs as a future therapeutic target in burned patients.