The Effects Of IL-1ra On Apoptosis And Expression Of Its Regulatory Proteins (Fas/FasL) Of Corneal Allograft During Acute Immunological Rejection In Rat

Background:Corneal transplantation is the most successful form of organ transplantation, apoptosis of infiltrating cells on the corneal allograft resulting from Fas-FasL interaction plays an important role in the high success rate of corneal transplantation. On the other hand, apoptosis which mediated by Fas/FasL is related with the immunologic rejection.Interleukin-1 is a potent proinflammatory cytokine that plays a critical role in initiating and maintaining immunogenic inflammation. We performed this experment to determine the relationship between IL-1ra and apoptosis mediated by Fas/FasL during the acute immunolocical rejection in experimental penetrating keratoplasty in rat. Objective:1. To investigate apoptosis and expression of apoptosis regulatory proteins Fas/FasL on normal corneas and corneal allografts in rats, and to analysis their roles in the corneal allograft rejection.2. To study the immunosuppressive effect of IL-lra and its effect on apoptosis and the expressions of regulatory proteins Fas/FasL on the corneal allografts during the acute immunological rejection in experimental penetrating keratoplasty in rat.Methods:Corneal transplantation was performed orthotopically from Wistar rats to SD rats, recipients were randomly assigned to three groups: group I was treated by N.S; group II was treated by CsA;. group III was treated by IL-lra; Treatments were began on the first postoperative day. Mean survival times were determined. The eyes of six rats were enucleated at random during the acute immunological rejection. Cellular morphologic changes of corneal buttons were evaluated by light and electron microscope examination.Apoptosis was determined by TdT-dUTP terminal nick-end labeling(TUNEL) assay. The immunohistochemistry combined computer-assisted image analysis was adopted to examine the expression and distribution of Fas/FasL proteins in comeal grafts during allograft rejection. At the same time, six corneas of normal Wistar rats were examined with above methods. Results:Mean survival time of transplants increased significantly in IL-1ra treated group compared with other groups. The coexistence of apoptosis and necrosis in rejected corneal buttons was observed when examined with electron microscopy. Fas protein was expressed in normal corneal epithelia, keratocyte, and endothelium. FasL protein, however, was detected in corneal epithelia and endothelium, but not in keratocyte. Apoptosis was present slightly in the epithelia in normal cornea. Apoptosis and expression of Fas/FasL proteins increased significantly during allograft rejection in the epithelium, endothelium and stroma of corneal allografts around the wound; The levels of apoptosis and expression of Fas/FasL proteins of IL-1ra treated group were markedly decreased when compared with other groups. Conclusions:1. Apoptosis and expression of Fas/FasL proteins exist in normal cornea.2. Apoptosis and expression of Fas/FasL proteins may involve in the acute immunological rejection in penetrating keratoplasty.3. Apoptosis mediated by cytotoxic T-lymphocyte (CTL) plays an important role in the immunological rejection of keratoplasy.4. Topical treatment with IL-lra has more significantly positive effect in promoting corneal allograft survival through Fas/FasL pathway than CsA treatment.