Abstract
BACKGROUND: Mesenchymal stem cells (MSCs) have been reported to promote long-term cellular and organ transplant acceptance due to their immunotherapeutic characteristics. Previous work from our lab using a rat allograft model has shown that systemic infusion of MSCs inhibited corneal allograft rejection and prolonged graft survival. Here, we further investigated the effects of local MSCs administration in the same animal model. METHODS: Donor-derived MSCs were isolated and cultured while corneal grafts obtained from Wistar rats were transplanted into Lewis rat hosts. Hosts were then randomly separated into four groups and treated with previously cultured MSCs at different times and doses. Graft survival was clinically assessed using slit-lamp biomicroscopy and the median survival time (MST) was calculated. Grafts were examined histologically using hematoxylin-eosin (H-E) staining and immunohistochemically using antibodies against CD4. A comprehensive graft analysis of IL-2, IL-4, IL-10, and IFN-γ expression was also conducted using both real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). RESULTS: Postoperative MSCs injection prolonged graft survival time when compared with controls (MST 9.8 ± 1.2 days). Injection twice of MSCs (MST 12.6 ± 1.4 days) was more effective than a single injection (MST 10.8 ± 1.3 days). MSCs-treated groups also showed suppression of inflammatory cell as well as CD4 + T cell infiltration in the allograft region. IL-4 and IL-10 levels were significantly increased in grafts obtained from postoperative twice MSCs-treated rats when compared with controls. There were no significant differences in IL-2 or IFN-γ expression across groups. CONCLUSIONS: Subconjunctival injection of MSCs in rats was effective in prolonging corneal allograft survival. This effect was mediated by inhibition of inflammatory and immune responses, indicating an anti-inflammatory shift in the balance of T helper (Th)1 to T helper(Th) 2.