Abstract
Abstract: :
Purpose:To examine the mode of action and efficacy of sub–retinal transplantation to the P23H rat, a model for autosomal dominant retinitis pigmentosa, at a stage before total loss of rod photoreceptors. Methods:P23H transgenic rats (40day old) received sub–retinal grafts of early postnatal retinae, which had been gently dissociated. Graft survival and integration with host retinae were examined by histology and function was assessed– using ERG. The graft location was first examined on cresyl violet sections, then specific markers( recoverin, PKCα, rhodopsin, calbindin, vimentin, mGlu6, bassoon ) were used to compare the changes of the major retinal neurons in the region of the graft and more distant. Results:The grafts survived and covered large areas of host retina. Most of the grafted cells were photoreceptors (as indicated by recoverin antibody staining) and showed inner and outer segments.A significant area of host retina close to graft had up to 5 layers of well preserved photoreceptors, and they formed organized inner and outer segments (indicated by rhodopsin and recoverin antibody staining) while distant from the graft there was only one row photoreceptors remaining.. At the time of transplantation, rod bipolars had already lost most of their dendrites, but in regions of preserved retina the dendrites had regenerated. Distant from the graft, such dendrites were not seen. Horizontal cell processes were well organized compared to regions distant from the graft where processes were poorly developed. The synaptic interface between bipolar cells and photoreceptors as indicated by mGluR6 and bassoon staining showed a near continuous lamina of staining, which contrasted with the periphery of the retina where staining was discontinuous and randomly disposed ERG recordings indicated preservation of b–wave amplitude in 6 out of 15 eyes examined at 63 days of age. Conclusions:Retinal grafts can rescue and repair retinal circuitry both anatomically and functionally in degenerated retina. The rescue of host photoreceptors and connectivity seen close to graft might be due to the trophic factors released by the retinal graft. The integration between host and donor tissue is under investigation.
Keywords: retinal degenerations: cell biology • transplantation • immunohistochemistry