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Qualitative identification of human retinal pigment epithelial (hRPE) cells attached to microcarriers : a potential new cell therapy for Parkinson’s disease Flores, Joseph

Abstract

Parkinson's disease (PD) is a neurodegenerative disorder that is characterized by the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta, leading to striatal DA depletion. Cell therapies such as human fetal cell transplants, which replace depleted DA by transplanting DA-producing cells, have been studied as a form of treatment. However, unconvincing clinical results and ethical and logistical hurdles have deemed such therapies unsuccessful. Human retinal pigment epithelial (hRPE) cells have been recently proposed as a tissue transplant alternative for PD. HRPE cells produce L-DOPA as part of the eumelanin pathway, they are easily grown in culture and can be stored for extended periods of time. Furthermore, when attached to gelatin microcarriers (hRPE-GM), immunosuppression is not needed. Recent studies in non-human primates, as well as open label studies in PD patients, have shown complete, / sustained reversal of parkinsonian symptoms without complications. However, there is no data on hRPE cell survival in the host. In this thesis, methods were developed to morphologically characterize hRPE-GM in vitro and to assess its short-term and long-term survival when implanted into the brain. Human RPE cells were grown to confluence in culture, harvested and passively attached to 45-63μm diameter gelatin microcarriers. In vitro HRPE-GM was immunohistochemically (IHC) characterized by using a human specific (NuMA Ab2) and epithelial specific (EMMPRIN) antibody. Next, fourteen male Sprague Dawley 6-OHDA lesioned rats receiving a unilateral striatal hRPEGM implant (without immunosuppression) were processed for IHC and ultrastructural electron microscopy (EM) analyses at various time points post-implant. A histological analysis revealed NuMA- and EMMPRIN-positive cells attached to the microcarriers in vitro and in vivo at various times post-implant. EM confirmed these results: morphologically characterized hRPE cells were seen at 48 hrs and 5 months post-implant. These results support the long-term survival of hRPEGM in the rat without immunosuppression.

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