AIM: To study the influences of dexamethasone on the immunogenicity of porcine cornea cryopreserved in liquid nitrogen and the involved mechanism.

METHODS: Fresh porcine corneas were drilled down by 13mm-diameter trephine. Then the samples were put into four kinds of cryoprotectants in turn for cooling equilibrium with “simplified four-step” method and then stored in liquid nitrogen. All samples were thawed in water at 40℃ before being used. The samples treated with dexamethasone were made and the preceding three cooling steps were same. But the samples were additionally incubated in 0.01, 0.03, 0.05mg/mL dexamethasone for 18h at 4℃ before the last cooling step. Totally 50 BALB/c mice were randomly divided into 5 groups including 10 mice in each group: the control group; routine cooling group which were treated through four cooling steps; dexamethasone group I, dexamethasone group II and dexamethasone group III which were treated with 0.01, 0.03, 0.05mg/mL dexamethasone successively. After treatment, corneal samples were transplanted into the hypodermis on the back of mice. After 14d, the samples were taken out, imbedded in paraffin, and stained by HE and CD25/FasL immunohistochemistry. All the samples were investigated under light microscope.

RESULTS: On the 14th day, all the samples were taken out. We found the samples which adhered to surrouding tissues swelled obviously and showed translucent and a bit yellow. Through HE staining, fresh corneal samples in the control group were infiltrated with large amount of lymphocytes throughout each layer; the amount of infiltrating cells in the routine cooling group was less than the control group in which most cells were distributed in endodermis and epitheliums. In the dexamethasone-treated groups, the amount of infiltrated cells were the least. Immunohistochemical results showed that compared with the the routine cooling group and dexamethasone-treated groups, the amount of CD25 and FasL in the control group was the most, the difference was significant. Compared with dexamethasone-treated groups, the amount of CD25 and FasL positive infiltrating cells in the routine cooling group were more. ALL the differences were significant. But there was no significant difference in the amount of CD25 and FasL positive infiltrating cells among each dexamethasone treated group.

CONCLUSION: Corneas in dexamethasone-treated groups showed the lowest immunogenicity. Corneal immunogenicity was irrelevant with the concentration of dexamethasone at the range of 0.01-0.05mg/mL.