title: Long-term survival of photoreceptors transplanted into the adult murine neural retina requires immune modulation.
abstract: Stem cell therapy presents an opportunity to replace photoreceptors that are lost as a result of inherited and age-related degenerative disease. We have previously shown that murine postmitotic rod photoreceptor precursor cells, identified by expression of the rod-specific transcription factor Nrl, are able to migrate into and integrate within the adult murine neural retina. However, their long-term survival has yet to be determined. Here, we found that integrated Nrl.gfp(+ve) photoreceptors were present up to 12 months post-transplantation, albeit in significantly reduced numbers. Surviving cells had rod-like morphology, including inner/outer segments and spherule synapses. In a minority of eyes, we observed an early, marked reduction in integrated photoreceptors within 1 month post-transplantation, which correlated with increased numbers of amoeboid macrophages, indicating acute loss of transplanted cells due to an inflammatory response. In the majority of transplants, similar numbers of integrated cells were observed between 1 and 2 months post-transplantation. By 4 months, however, we observed a significant decrease in integrated cell survival. Macrophages and T cells were present around the transplantation site, indicating a chronic immune response. Immune suppression of recipients significantly increased transplanted photoreceptor survival, indicating that the loss observed in unsuppressed recipients resulted from T cell-mediated host immune responses. Thus, if immune responses are modulated, correctly integrated transplanted photoreceptors can survive for extended periods of time in hosts with partially mismatched H-2 haplotypes. These findings suggest that autologous donor cells are optimal for therapeutic approaches to repair the neural retina, though with immune suppression nonautologous donors may be effective.
authors.affiliation: Department of Genetics, University College London Institute of Ophthalmology, London, United Kingdom.
authors.forename: Emma L
authors.initials: EL
authors.lastname: West
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Pearson
authors.forename: Susie E
authors.initials: SE
authors.lastname: Barker
authors.forename: Ulrich F O
authors.initials: UF
authors.lastname: Luhmann
authors.forename: Robert E
authors.initials: RE
authors.lastname: Maclaren
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Barber
authors.forename: Yanai
authors.initials: Y
authors.lastname: Duran
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Smith
authors.forename: Jane C
authors.initials: JC
authors.lastname: Sowden
authors.forename: Robin R
authors.initials: RR
authors.lastname: Ali
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D016572:Cyclosporine / Q000627:therapeutic use; D005434:Flow Cytometry; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D010786:Photoreceptor Cells / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D033581:Stem Cell Transplantation / Q000379:methods*; D013601:T-Lymphocytes / Q000276:immunology; D013997:Time Factors
chemical_list: D007166:Immunosuppressive Agents; D016572:Cyclosporine