Bone marrow-derived progenitor cells promote corneal wound healing following alkali injury

Purpose To determine whether bone marrow-derived progenitor cells can be stimulated by inflammatory mediators and play a role in corneal wound healing following alkali injury. Methods Sixty rabbits were divided into two groups (Group I and Group II). Group I served as a bone marrow-suppression model, and received 200 mg/kg cyclophosphamide. Corneal alkali injury was created in one eye of each rabbit in each group; the other eye served as control. Three days after corneal burn, inflammatory cells in peripheral blood were counted. At the end of 4 weeks follow-up, corneas of all rabbits were subjected to histochemical examination to assess infiltrated CD34 and C-kit positive cells. Clinical outcome was determined at the end of 4 weeks. Results Cyclophosphamide suppressed bone marrow function in Group I by reducing cellularity by more than 30% and neutrophil distribution by 3.18 +/- 1.83%. The number of bone marrow hematopoietic and mesenchymal progenitor cells were all suppressed by cyclophophamide, as demonstrated by statistically significant differences between Group I and Group II of CD34+ cells (t=-21.62, P < 0.01) and C-Kit cells (t=21.62, P < 0.01). Fewer inflammatory cells were released into circulation in Group I (14.42 +/- 5.70%) than in Group II (44.36 +/- 8.64%). Clinical observation revealed that Group II rabbits had much greater reepithelization (t=6.999, P < 0.01) and clearer corneas (X-2=4.417, P < 0.01) than Group I. Conclusion Corneal alkali injury is a stimulus that induces a rapid bone marrow reaction to release not only inflammatory cells but also progenitor cells into circulation. Migrated bone marrow-derived progenitor cells can home to local sites to promote wound healing.