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S.R. Sadda, G. Qiu, M.J. Seiler, B.B. Thomas, R.B. Aramant, E. de Juan, Jr; Characteristics of Retinal Progenitor Cells: Subretinal Transplantation versus in vitro Induction . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3222.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Retinal progenitor cells (RPCs) have been advocated as a potential treatment for retinal degenerative diseases. The purpose of this study was to compare the characteristics of RPCs, following transplantation in retinal degenerate rodents versus in vitro induction with retinoic acid. Methods: RPCs were isolated from embryonic day 17 (E17) human alkaline phosphatase (hPAP)–positive rat retina, and expanded in serum–free defined media supplemented with epidermal and basic fibroblast growth factor. For in vitro experiments, cells at Passage (P) 2 were induced for 8 days with all trans retinoic acid, and then characterized (for their differentiation phenotype) by immunocytochemistry and RT–PCR. For in vivo studies, P2 RPCs were transplanted into the subretinal space of one eye of S334–3 retinal degenerate rats in three different age groups (postnatal day 17, 28, and 48). Optokinetic visual behavioral testing was performed at post–op weeks 2, 3, 4 and 8. Characteristics of the transplanted RPCs were evaluated by immunohistochemistry. Results: Following in vitro induction, RPCs differentiated into various retinal specific neurons expressing rhodopsin, PKC, and calbindin. Co–expression of nestin with these end–stage retinal specific markers was also observed. RT–PCR analysis showed that differentiated cells expressed both early and late stage developmental genes (CRX, Pax6, opsin, GFAP). Following transplantation, 36% of animals showed preservation of optokinetic visual responses in the transplanted eye compared to the fellow control eye (p<0.01). Transplanted cells organized into sheets with extension of some graft cell processes into the host retina. Synapsin–1 positive neural processes were present at the graft–host interface. In all age groups, retinal–specific neuronal differentiation was observed, including recoverin or rhodopsin staining in 80% of grafted cells. Less than 5% of the grafted cells expressed GFAP. In contrast to in vitro studies, nestin co–expression was not observed. Conclusions: Grafted RPCs can demonstrate extensive rhodopsin expression and organize into a sheet of cells following subretinal transplantation in retinal degenerate rats. The lack of nestin co–expression, an apparent transient phenomenon during retinal cell maturation, in transplanted RPCs may reflect a further level of differentiation towards a mature neuron compared with in vitro induction.
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