Effects of MHC conformity on corneal epithelial cell sheet transplantation in non-human primates

Abstract

Purpose : Transplantation of HLA-homozygous corneal epithelial cell sheet (CEC sheet) derived from induced pluripotent stem cells (iPSCs) is a potential new treatment of limbal stem cell deficiency.
However, the effects of HLA concordance on the CEC sheet transplantation are not addressed yet.
Here, we investigated the difference in immune response to the MHC-homozygous CEC sheets and the effect of the donor cell engraftments in MHC-matched and unmatched non-human primates.
We also conducted mixed lymphocyte reaction (MLR) between human somatic or iPS-CECs and peripheral blood mononuclear cells (PBMCs), and investigated the immunogenicity and the difference in immune response due to HLA compatibility of CEC sheets.

Methods : A CEC sheet donated from a cynomolgus monkey with homozygous MHC haplotypes was transplanted to the limbal stem cell deficiency model of 7 cynomolgus monkeys having heterozygous MHC haplotypes (3 MHC-matched models) or non-identical MHC alleles (4 MHC-unmatched models).
Steroid and immunosuppressant were not administered after the transplantation.
The observation period was 3 months (2 MHC-matched and 3 MHC-unmatched monkeys) or 6 months
(1 MHC-matched and 1 MHC-unmatched monkey).
In addition, human somatic cells or iPSCs were co-cultured with PBMCs and the amount of IFN-γ in the culture supernatant was measured by ELISA.

Results : In the CEC sheet transplantation of cynomolgus monkey, acute rejection caused by CEC sheet transplantation did not occur (0/3) in MHC-matched monkeys, and occurred at 1/4 in MHC-unmatched monkeys.
In MHC-unmatched monkeys showed no acute rejection, increased conjunctival injection, corneal thickness, and the area of blood vessels in the central cornea were observed, whereas these findings remained flat 2-3 months after transplantation in MHC-matched monkeys.
Moreover, the K12 (specific marker of corneal epithelial cells) positive area at 6 M after transplantation was lower in MHC-unmatched monkey than in MHC-matched monkey.
In human MLR, there was no significant change in IFN-γ production between somatic CECs and iPS-CECs when they were mixed with PBMCs, and also no significant difference between HLA-matched and unmatched combination.

Conclusions : In iPS-CEC sheet transplantation, severe immune rejection was not induced even in MHC-unmatched transplantation, though the response was further suppressed by adapting MHC.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.