Circulating progenitor cells and the expression of Cxcl12, Cxcr4 and angiopoietin-like 4 during wound healing in the murine ear.

Migration of cells from both local and systemic sources is essential for the inflammatory and regenerative processes that occur during normal wound healing. CXCL12 is considered a critical regulator of CXCR4-positive cell migration during tissue regeneration. In this study, we investigated the expression of Cxcl12 and Cxcr4 during healing of a murine full thickness ear wound. We also investigated the expression of angiopoietin-like 4, which has been shown to participate in wound angiogenesis and reepithelialization. At time points up to 48hrs, complete blood counts were performed using automated hematology analysis, and the numbers of circulating stem and progenitor cells quantified using flow cytometry. Expression of both Cxcr4 and Angptl4 was significantly elevated within 3 days of wounding, and both were strongly expressed in cells of the epidermis. ANGPTL4 protein expression remained elevated in the epithelium through day 14. Cxcl12 expression was increased significantly at day 3, and remained elevated through day 21. Faint Cxcl12 staining was detectable in the epithelium at day 1, and thereafter staining was faint and more generalized. There were significantly fewer circulating total white blood cells and lymphocytes 1hr following ear punching. Similarly, there was a significant early (1hr) reduction in the number of circulating endothelial progenitor cells. Further studies are warranted to investigate whether ANGPTL4 and CXCL12/CXCR4 interact or synergize to facilitate cell recruitment and migration, and to potentiate reepithelialization and wound healing.