The Experimental Study On Rapamycin In Prevention Of Rat Corneal Allograft Rejection And Neovascularization

ObjectiveTo investigate the effects of rapamycin on prevention of corneal allograft rejection in murine corneal transplantation and on inhibition of corneal neovascularization induced by sutures.Methods1.The outbred strains SD and Wistar rats were used as donors and recipients, respectively. The grafts were evaluated clinically and histologically at various time points after operation. Mixed lymphocyte culture assay, using lymphocytes from recipients of penetrating keratoplasty as responder cells and irradiated splenocytes from SD or Brown Norway as stimulator cells, was used to identify allogenic stimulation.2. The Wistar rats were divided into four groups: group 1, autograft control; group 2, allograft control, were given placebo; group 3 and 4, allograft groups, were administered orally RAPA 3mg/kg d and CsA 10mg/kg d, respectively. The drugs were delivered for 12 days beginning at the day of transplantation. The grafts were compared clinically and histologically.3. A model of corneal angiogenesis was developed by the placement of sutures in the SD rat cornea. The rats were divided into three groups: group 1 were administered with the solution without drugs; group 2 and 3 were treated with RAPA0.1ml (1mg/ml) and Dexamethasone 0.1ml (2mg/ml), respectively, by parabulbar injection. The drugs were given once every three days for two weeks beginning at the day of suturing. Corneal neovascularization was quantified with image analysis software IPP4.5, and the data were analyzed statistically. Immunohistochemical study was carried out for VEGF expression.Resultsl.Allogenic keratoplasty between SD and Wistar rats led to corneal rejection in 100% of cases. Histological examination showed stromal edema and marked mononuclear cell and lymphocyte infiltration. In mixed lymphocyte culture assay, Wistar rats had been primed to allogenic stimulation at the time of cornea transplantation.2.Therapy with RAPA 3mg/kg d led to a statistically significant prolongation of transplant survival compared with the control group(P<0.05), and the similar efficacy was seen in the CsA group. In RAPA group, corneal neovascularization was markedly reduced. Fewer inflammatory cells were found in the corneal stroma of the two therapy groups.3. In RAPA and Dexamethasone groups, corneal neovascularization was significantly suppressed (P<0.05). The expression of VEGF was significantly reduced in the RAPA group(P<0.05).Conclusions1.In rat allogenic keratoplasty models, all corneal grafts are rejected in approximately 2 weeks, and the clinical evaluations are confirmed by histologic and cytological studies.2.Systemic RAPA therapy can prevent corneal graft rejection and corneal neovascularization.3.Topical RAPA treatment is an effective way of suppression corneal neovascularization and the expression of VEGF.