Initial experimental study on pig-rhesus corneal xenotransplantation

Abstract

To investigate pig-rhesus corneal xenografting rejection characterization and evaluate the effect of glucocorticoids on the grafts survival. Wuzhishan pigs (WZSP) donor corneas were grafted orthotopically into rhesus recipients. 12 rhesus monkeys were divided into two groups: group control and group steroid treatment. Recipients in group steroid treatment were injected with compounded betamethasone 0.5 ml (7 mg/ml) subconjunctivally at the end of the operation, 0.3 ml after operation at 10 days interval for 10 total times. The group control received saline buffer in the same way. All xenografts were evaluated by slit-lamp microscopy. One month after surgery, two recipients in each group were sacrificed for corneal histopathological staining. The concentration of cytokines (IFN, TNF, IL-4, IL-5, IL-10) in the aqueous humor and blood of the recipients, the level of immunoglobulin IgG, IgA, IgM and complement C3, C4 in the blood were detected before surgery and at different timepoint after keratoplasty. The percentage of CD4+, CD8+, CD16+ T lymphocyte was examined by cytometry. The mean survival time (MST) of xenografts was (15.5 +/- 2.3) days in group control and (182.8 +/- 66.1) days in group steroid treatment. In group control, corneal xenografts showed exudative membrane in the anterior chamber, diffuse edema, and new-forming vessels growing at the peripheral corneal bed. In group steroid, the grafts were transparent and showed slight edema. Histopathological examination showed that in group control, corneal xenografts were infiltrated with inflammatory cells. The corneal endothelia were destroyed and exudative membranes were attached onto the posterior of the grafts. In group steroid treatment, the corneal xenografts showed only minimal edema and inflammatory cells infiltrated. The xenografts endothelium were intact and no exudative membrane appeared. In group control, the concentration of cytokines was increased 3 weeks after surgery than the level before surgery, especially IFN. In group steroid treatment, the changes of the cytokines were mainly the increase of IL-10 and IL-4, the concentration of IFN and TNF was decreased. The immunological analysis showed that the concentration of immunoglobulin IgG, IgA, IgM and complement C3, C4 in group control was mainly increased at 2 - 3 weeks after surgery, in group steroid, the change of the concentration of IgG and C4 was different compared with group control. Endothelium rejection occurred in pig-rhesus corneal xenografts. The humor immune factors might involve grafts rejection reaction. The glucocorticoid was effective on delaying corneal xenotransplantation rejection.