Abstract
Abstract: :
Purpose: Characterization of inflammatory responses induced by injection of cultured adult, retinal pigment epithelium (RPE) cells into the subretinal space (SRS) of syngeneic and allogeneic recipients. Methods: RPE cells obtained from the eyes of adult C57BL/6 mice were cultured for two weeks, mixed with 1x105 microbeads, and then implanted (1x105 RPE in 2 µl) into the subretinal space of both eyes of adult C57BL/6 and BABL/c mice. Mice were sacrificed at weekly intervals thereafter and eyes were removed. One eye was fixed with 4% paraformaldehyde, embedded with paraffin, 5µm sections prepared and stained with hematoxylin–eosin. The other eye was collagenase digested, rendered into a single cell suspension, stained with fluorochrome labeled anti–CD8, anti–Thy1.2, and anti–CD45 antibodies and then examined by flow cytometry. Results: Histology results showed no inflammation at any time from 1 to 4 weeks after transplanting RPE into syngeneic recipients. However, local retinal swelling, disruption of the photoreceptor layer, and infiltration of inflammatory cells was found in the SRS of allogeneic recipients beginning at 2 weeks and peaking by 3 weeks. By 4 weeks, the inflammatory response had subsided but the presence of microbeads verified that the RPE had been injected into the SRS. Flow cytometry showed that the eyes of normal C57BL/6 and BABL/c mice contained 50 to 200 CD8+ T cells, presumably contributed by the blood in the ocular vasculature. Two weeks after subretinal injection with RPE similar numbers of T cells were found in the eyes of syngeneic recipients, but approximately 100–fold more T cells (14,713 ± 8,011) were found in the eyes of BALB/c recipients of B6 RPE, which was significantly different from syngeneic recipients with three recipients per group. Conclusions: Cultured RPE cells survive in the SRS of syngeneic mice, whereas they induce a strong inflammatory response in allogeneic mice that peaked at three weeks. Inflammatory responses resolved quickly but the microbeads served as a good marker to verify that RPE had been injected into the SRS.
Keywords: retinal pigment epithelium • transplantation • inflammation