ABSTRACT
BackgroundAn ideal animal model is very important for the investigation of the immune mechanism of high-risk rejection corneal transplantation.ObjectiveThis study was to compare three methods of creating a high-risk corneal transplantation model in rabbits to study high-risk rejection corneal transplantation.MethodsForty-five New Zealand white rabbits were utilized and assigned randomly to three groups of different modeling methods,with 15 rabbits for each group.The high-risk corneal transplantation models were created by suturing with 5-0 silk thread in 4 quadrants,inducing alkali burn with 1 mol/L NaOH or corneal xenotransplantation.In the suturing group and alkali burning group,the rabbits received a unilateral 7.25 mm diameter corneal allograft after corneal neovascularization was induced,and in the xenotransplantation group,corneas from cats were used as donors.Rabbits were followed-up for 4 weeks in all groups.Corneal neovascular area was calculated and compared among the three groups.The amount of rejection,inflammatory index ( IF),neovascularization and histology of grafts were clinically scored to calculate the reject index (RI).ResultsThere were 14,15 and 15 rabbits that survived the high-risk penetrating corneal transplantation,respectively,in the suturing group,alkali burning group and xenotransplantation group.Two weeks after operation,the IF scores were 0.543 ± 0.103,0.811 ± 0.054 and 0.191 ±0.087,and the RI were 2.111±0.928,7.0±0.816 and 3.182±0.751 in the suturing group,alkali burning group and xenotransplantationgroup,respectively,showingstatisticallysignificantdifferencesamongthethreegroups (x2 =25.736,22.432,P =0.000).The IF value was lower in the xenotransplantation group compared with the suturing group and alkali burning group (Z =3.841,3.993,P =0.000),and that of the suturing group was lower than the alkali burning group (Z =3.568,P =0.000).The RI value of the xenotransplantation group was significantly raised in comparison with the suturing group and declined in comparison with the alkali burning group (Z =2.373,P =0.018;Z =3.936,P =0.000),and that of the suturing group was lower than the alkali burning group (Z =3.729,P =0.000 ).The survival times of the grafts were ( 17.9±2.0 ) days,( 13.4 ±2.4) days and ( 15.5 ±2.0 ) days in these three groups with a significant difference among them ( F =9.474,P =0.001 ).The neovascularization area in the xenotransplantation group was smaller than the suturing group and alkali burning group (P＜ 0.05 ).Histological examination revealed a large number of inflammatory cells infiltration in the grafts 2 and 4 weeks after transplantation in the suturing group and alkali burning group,but less inflammatory cells were seen in the xenotransplantaion group.Immunofluorescence staining showed abundant CD4+ T positive cells in the grafts in the three groups.Conclusions The cat-rabbit corneal xenotransplantation can induce stable and moderate immune rejection.This animal model has milder inflammatory response and less corneal neovascularization than the suture and alkali burn models.This method therefore is an ideal model for high-risk corneal transplantation.