Cox-2 inhibition potentiates mouse bone marrow stem cell engraftment and differentiation-mediated wound repair

Background. Engraftment of transplanted stem cells is often limited by cytokine and noncytokine proinflammatory mediators at the injury site. We examined the role of Cyclooxygenase-2 (Cox-2)-induced cytokine-mediated inflammation on engraftment of transplanted bone marrow stem cells (BMSCs) at the wound site. Methods. BMSCs isolated from male C57/BL6J mice were transplanted onto excisional splinting wounds in syngenic females in presence or absence of celecoxib, Cox-2 specific inhibitor (50 mg/kg, body weight [b wt]), to evaluate engraftment and wound closure. Inflammatory cell infiltration and temporal expression of inflammatory cytokines at the wound bed were determined using immunohistochemical and quantitative real time polymerase chain reaction (qPCR) analysis, respectively. Mechanistic studies were performed on a murine macrophage cell line (F774.2) to evaluate the effect of interleukin (IL)-17A. Results. Celecoxib administration led to a significantly high percent of wound closure, cellular proliferation, collagen deposition, BMSCs engraftment and re-epithelialization at the wound site. Interestingly, recruitment of CD4(+)T cells and F4/80(+) macrophages as well as BMSC transplantation induced up regulation of Cox-2 and IL-17A gene expression levels were reverted by celecoxib administration. Exogenous supplementation of recombinant interleukin (rIL)-17 to F7774.2 cells significantly increased proliferation and gene expression of cytokines-IL-1 beta, IL-6, IL-8, IL-18 and tumor necrosis factor (TNE)-alpha via nuclear translocation of nuclear factor kappa B (NE kappa B)p65/50 subunit. Conditioned media of rIL-17 treated F7774.2 cells when supplemented to BMSCs depicted a dose-dependent increase in the number of apoptotic cells and proapoptotic protein expression that was perturbed by celecoxib or IL-17 neutralizing antibody. Finally, celecoxib led to a dose-dependent increase in BMSC differentiation into keratinocyte-like cells in vitro. Conclusion. Celecoxib protects transplanted BMSCs from Cox-2/IL-17-induced inflammation and increases their engraftment, differentiation into keratinocytes and re-epithelialization thereby potentiating wound tissue repair.