To investigate the effect of mesenchymal stem cells (MSCs) combined with low-dose cyclosporin A (CsA) on corneal transplantation rejection and its mechanism.

A fully allogeneic rat cornea transplant model (Wistar rats to Lewis rats) was created.Thirty-six model rats were divided into MSCs group, CsA group and MSCs+ CsA group randomly by using the random number table method, with 12 rats for each group.In each group, six rats were used for the evalution of symptom observation and six for the assay of immune factor.Three days after corneal transplantation, slit lamp microscope was used to observe and record the vascularization, edema and opacity scores of corneal graft.After 18 days, spleen T helper cell(Th)1 and Th2 cytokines were measured by enzyme linked immunosorbent assay(ELISA). The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.This study protocol was approved by Ethic Committee of Tianjin Medical University Eye Hospital (No.TMUaMEC2017028).

The survival time of corneal grafts in MSCs+ CsA group was prolonged in comparison with the MSCs group and CsA group, with significant differences between them([21.3±3.9]days vs. (14.8±2.4)days; [21.3±3.9]days vs.[16.0±1.1]days) (P=0.003, 0.004). Eighteen days after corneal transplantation, corneal opacity scores were 3.17±0.17, 3.00±0.00 and 2.17±0.17, corneal neovascularization scores were 2.67 ± 0.21, 2.33 ± 0.21 and 1.83 ± 0.21, respectively in the MSCs group, CsA group and MSCs+ CsA group, showing significant differences among the three groups (F=15.500, P<0.01; F=4.524, P=0.029). The corneal opacity scores and corneal neovascularization scores in the MSCs+ CsA group were significantly lower than those in the MSCs group and CsA group(all at P<0.05). Interleukin(IL)-2, IL-4, IL-10, and interferon-γ (IFN-γ) concentrations were all significantly different among the MSCs group, CsA group and MSCs+ CsA group (F=15.000, 12.810, 10.720, 17.960, all at P<0.01). Compared with the MSCs group and CsA group, Th1 subsets cytokines IFN-γ and IL-2 concentrations in the MSCs+ CsA group were significantly lower, and Th2 subsets cytokines IL-4 and IL-10 concentrations were significantly increased in the MSCs+ CsA group in comparison with the MSCs group and CsA group (all at P<0.05).

The combination of MSCs with low-dose CsA can effectively ameliorate immunological rejection by the modulation of the balance of Th1/Th2.

Mesenchymal stem cells; Immunosuppressant; Corneal transplantation; Rejection