In vitro characteristics and in vivo outcome of α1,3-galactosyltransferase gene-knockout miniature pig cornea in full-thickness corneal xenotransplantation using nonhuman primate

Abstract

Purpose : Recent studies showed α1,3-galactosyltransferase gene-knockout (GTKO) pig corneas were not associated with prolonged full-thickness corneal xenograft survival in nonhuman primates, while the mechanism was not known well. We investigated the biofunctional profiles of GTKO miniature pig cornea and its outcome in pig-to-rhesus full thickness corneal xenotransplantation.

Methods : Ten eyes of GTKO (n=3) and GTKO/CD39 knock-in (n=2) miniature pigs were used to evaluate the physical and functional characteristics. Five Chinese rhesus macaques underwent full thickness corneal xenotransplantation (mean donor age: 11.3 mo). Systemic tacrolimus, basiliximab, and IVIG were administered as programmed schedules. T cell subsets, anti-αGal, and non-αGal antibodies (Ab) in the blood, and C3a levels in aqueous humor (AH) were evaluated. The results were compared with those of the wild type miniature pig corneal grafted group (n = 4, all grafts survived > 24 weeks, using anti-CD154 Ab) as controls.

Results : Mean central corneal thickness was 763 μm, and the Na⁺/K⁺-ATPase was well expressed 7 days after preservation. Mean endothelial cell density was 4729/mm², and was well maintained >2800/mm² through 7 days. Mean doubling time was 30.4 hour which was comparable to that in SNU miniature pigs (30.7 hour, P=0.413). The median graft survival was 72 days. Regulatory T cells at rejection decreased from baseline (p=0.043) and were lower than those of controls at postoperative 24 weeks (p=0.014), however the other T cell subsets did not change. Anti-αGal Ab did not increase during the follow-up. At rejection, anti-non-αGal Ab increased from baseline (p=0.043). C3a in AH at postoperative 4 weeks and at rejection increased from baseline (all p=0.043). At postoperative 4 weeks, mean AH and plasma C3a concentrations were higher than those of controls (p=0.016 and 0.036, respectively).

Conclusions : The biofunctional characteristics of GTKO miniature pig cornea are feasible for corneal xenotransplantation. Rejection of GTKO pig-to-rhesus full-thickness corneal xenotransplantation is related with non-αGal Ab, complement and decrease of regulatory T cells. Addition of B cell suppressing regimen should be considered.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.