Abstract
Abstract: :
Purpose: To evaluate the fate of the amniotic epithelium heterotopically transplanted as an allograft on the ocular surface, and to determine whether allogeneic amniotic epithelium sensitizes recipients. Methods: Amniotic epithelium (AE) was prepared, as an intact sheet from placentas of 18 day-pregnant enhanced green fluorescence protein (EGFP) transgenic mice (C57BL/6 background) and wild type C57BL/6 mice. Segments of amniotic epithelium (approximately 2 x 1mm) were transplanted on the cornea or the conjunctiva of normal BALB/c eyes by 2 interrupted sutures (11-0 nylon). Recipient eyes were removed at 1, 4, 7, 10, 14, 21 and 28 days, and tissue sections were prepared. Fluorescence microscopy was used to detect GFP positive donor cells in the tissue sections. Expression of GFP was confirmed immunohistochemically using anti-GFP antibody. Recipients were evaluated for acquisition of donor-specific delayed hypersensitivity (DTH) at 2, 4 and 8 weeks. Results: Allogeneic AE grafts induced cell infiltration and neovascularization in the cornea and in the conjunctiva at the suture area. GFP positive cells were disappeared in EGFP donor-derived AE grafts on the conjunctiva within 7 days. Whereas, in AE grafts on the cornea at 10 days, GFP positive cells were found in the corneal stroma at the sutured areas, but not on the corneal surface. These GFP positive cells were not detected at 14 days. AE allografts on the cornea induced donor-specific DTH at 2 weeks, but they failed to induce at 4 and 8 weeks. On the other hands, AE allografts on the conjunctiva induced DTH at both 2 and 4 weeks, and failed to induce at 8 weeks. Conclusion: Freshly isolated allogeneic AE is immunogenic and sensitizes recipients, when placed on the ocular surface. Survival of amniotic epithelial cells in the conjunctiva is shorter than that in the cornea, and sensitization by AE grafts on the conjunctiva is stronger than that on the cornea.
Keywords: transplantation • immune tolerance/privilege • antigen presentation/processing