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M.J. Seiler, S. Chadalavada, B.B. Thomas, Z. Chen, S. Arai, M.J. Mahoney, S.R. Sadda, R.B. Aramant; No Apparent Rescue of Cones and Synaptic Proteins in Degenerated Retinas by Retinal Sheet Transplants . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1406.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate distribution of cones and expression of postsynaptic density protein PSD95 in degenerated S334ter retinas after subretinal transplantation of retinal sheets.
Sheets of E19 rat retina expressing human alkaline phosphatase (hPAP), coated with BDNF microspheres, were transplanted to the subretinal space of 4–6 week old S334ter–3 rats with fast retinal degeneration that had been exposed to blue light for 5 d. Visual responses were recorded from the superior colliculus (SC) of transplanted rats at the age of 3 months. Controls were rats without surgery, receiving transplants without BDNF, or BDNF microspheres only. Transplants and host retinas were analyzed by immunohistochemistry with markers for donor tissue (hPAP), photoreceptors and cone bipolar cells (recoverin), red–green (RG) opsin, and PSD95.
With low light (1cd/m2) stimulation, responses were recorded from the SC in a restricted area corresponding to the retinal location of the transplant (with or without BDNF microsphere coating). Transplants exhibited varying degrees of organization, from disorganized areas to lamination similar to normal retina. RG opsin immunoreactivity, normally found only in cone outer segments, stained cone cell bodies and processes in degenerated retinas. Transplant cones showed almost normal cone–opsin immunoreactivity in well laminated areas with photoreceptor outer segments, but in disorganized areas also cone cell bodies and processes stained. Occasionally, host cones sprouted processes into the transplant. Density of host cones over the transplant did not appear higher than outside the transplant area although cone densities were variable. In normal retina, strong PSD95 immunoreactivity was found in the outer plexiform layer, colocalizing with dendritic terminals of rod bipolar cells. In degenerate retina, immunoreactivity for PSD 95 was patchy and discontinuous. Immunoreactivity for PSD–95 was at normal levels in the transplant outer plexiform layer, however much less and only patchy in the host retina overlying and outside the transplant. No significant difference was seen between BDNF treated and untreated transplants.
Retinal sheet transplants can develop normal cones and strongly express PSD–95. However, in degenerated retina, the presence of a transplant does not appear to rescue or restore PSD–95 in bipolar synapses with photoreceptors.
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