Abstract
Purpose: :
Human amnion mesenchyme cell (hAMC)-derived side population cells (hAMC-SPCs) have the phenotype for neural progenitor when cultured under a particular condition and obtain the ability to differentiate to neuronal cells in vitro. We have reported that acute rejection is induced by cellular immunity after subretinal transplant of hAMCs. We analyzed the antigenicity of hAMC-SPCs when cultured in vitro and when transplanted into xenogeneic subretinal space.
Methods: :
Placenta was obtained at elective cesarean sections from volunteers, with informed consent. Cultured hAMC-SPCs were analyzed for expression of human major histocompatibility complex (MHC) class I and MHC class II antigens at 3, 7, 10, 14, 17, 21, 28 days after exposure to interferon gamma (IFN-g) at 33ng/ml using flow cytometry. As a different set of experiments, after staining with PKH26, cultured hAMC-SPCs were transplanted transsclerally to the subretinal space of normal eyes of 6-12 week-old C57BL/6 mice as normal recipients and rd6 mice injected intraperitoneally with cyclosporine A as immunodeficient retinal degeneration model (rd) recipients. Eyes were enucleated at 1, 2 and 4 weeks after transplantation, and were assessed immunohistochemically to evaluate survival of PKH26 positive cells and expression of MHC antigens on transplanted cells under confocal microscopy.
Results: :
In vitro culture, 80% of hAMC-SPCs displayed a low level of MHC class I before exposure to IFN-g. None of these cells expressed MHC class II. Expression of MHC class I was upregulated at 3 days exposure to IFN-g. Expression of MHC class II was also upregulated after exposure to IFN-g, however these expressions were reversible after removal of IFN-g. In vivo, PKH26 positive cells were identified in the subretinal space of both normal and immunodeficient rd recipients at 4 weeks after subretinal transplantation. PKH26 positive cells did not express either MHC class I or class II in mouse eyes. Neither CD4 nor CD8 positive cells were present in the eyes of either recipient.
Conclusions: :
hAMC-SPCs express no MHC antigens in the recipients' eyes after subretinal transplantation, and escape from T-cell infiltration. However, these cells have the potential to express MHC antigens in vitro. Therefore, hAMC-SPCs may have a risk of rejection after transplantation into an inflamed eye.
Keywords: transplantation • regeneration • immunomodulation/immunoregulation