Establishment of a murine model of chronic corneal allograft dysfunction

Background: To establish a murine model of chronic corneal allograft dysfunction (CCAD) that permits molecular evaluation of chronic allograft dysfunction after corneal transplantation. Methods: C57BL/6 (allogeneic), CB6F1 (semiallogeneic) and BALB/c (syngeneic) corneal grafts were transplanted orthotopically to BALB/c recipients and to the BALB/c mice as a control group. The follow-up time was more than 100 days. Graft survival time was monitored. Corneal endothelium was examined by alizarin red and PI/Hoechst stain. CD4 ⁺ and CD8⁺ T lymphocytes were examined by immunohistochemistry. Ultra-structure changes of the grafts were examined by electron microscopy. Results: Median graft survival times were 17 days, 85.5 days, and >100 days in allogeneic, semiallogeneic, and syngeneic groups respectively. Acute rejection episodes were observed only in the allogeneic group. A large amount of CD4⁺ and CD8⁺ T lymphocyte infiltration was present in allografts only in the allogeneic group, and few CD4⁺ and CD8⁺ T lymphocytes were observed in grafts in other groups. Large amounts of apoptotic and necrotic cells could be seen in the allogeneic group. Endothelial cell density decreased, and few apoptotic cells could be detected in semiallogeneic and syngeneic groups. No apoptotic or necrotic endothelial cells were found in the control group. Ultra-structural characteristic changes mainly included fibrosis formation, endothelium atrophy, and degeneration in failed grafts among transplant groups, as determined by electron microscopy. Conclusions: The changes in semiallogeneic and syngeneic groups after transplantation were similar to those observed during clinical study. Although differences between mouse strains and clinical situations remain to be explored, this murine model provides the basis for understanding the pathogenesis of CCAD.