Differentiation of adult human retinal pigment epithelial cells into dopaminergic-like cells in vitro and in the recipient monkey brain

Abstract

Background Cell therapy is proposed to be a potential treatment for Parkinson’s disease (PD). Although fetal retinal pigment epithelial (RPE) cells have been tested in trials for treating PD patients, controversy has been raised over the issue of whether such cells can be reprogrammed into dopamine-producing cells for therapeutic efficacy. Here, we aim to investigate whether adult human RPE cells can be reprogrammed into dopamine-producing cells both in vitro and in the recipient monkey brain. Methods The RPE layer was isolated from frozen posterior eyeball tissue after penetrating keratoplasty surgery. The tumorigenicity of RPE cells was examined by G-banding and a tumor formation assay in nude mice. Immunogenicity was measured using a one-way mixed lymphocyte reaction (MLR) assay. Dopamine-production in chemically reprogrammed RPE cells was measured by HPLC. Finally, RPE cells were grafted into the brains of monkeys with MPTP-induced PD in order to investigate the potential of such cells treating PD patients in the future. Results RPE cell lines have been successively established from adult human eye tissues. Such cells can be chemically reprogrammed into dopamine-producing cells in vitro. Moreover, after being grafted into the brain caudate putamen of monkeys with MPTP-induced PD, RPE cells became tyrosine hydroxylase-positive cells, and recipient PD monkeys showed significant improvement of clinical conditions. Conclusions This preclinical study using a primate model indicates that human adult RPE cells could be a potential cell source for the treatment of PD in the future. Electronic supplementary material The online version of this article (10.1186/s10020-019-0076-3) contains supplementary material, which is available to authorized users.

Application of Small Molecules in the Central Nervous System Direct Neuronal Reprogramming

“…The patterns of small-molecule cocktails in neuronal reprogramming are decided on the types of starting cells and whether it is under pathological conditions ( Hu et al, 2015 ; Li et al, 2019 ; Qin et al, 2020 ). However, the synergistic mechanisms of the used drug cocktails, remain unclear ( Vasan et al, 2021 ).…”

“…Li’s team found that adult human retinal pigment epithelial cells can transdifferentiate into dopaminergic-like cells in vitro following induction by a combination of SB431542, CHIR99021, and LDN193189. After transplanting the inducted cells into the brain, recipient PD monkeys showed significant improvement in clinical conditions ( Li et al, 2019 ). Another study showed that a cocktail consisting of VPA, Repsox, kenpaullone (another inhibitor of GSK-3β), forskolin, purmorphamine, and Y-27632 can convert human fibroblasts into dopaminergic neuron-like cells in vitro ( Qin et al, 2020 ).…”

Pigment Epithelia of the Eye: Cell-Type Conversion in Regeneration and Disease

“…Over the past 20 years, extensive information has accumulated, indicating the RPE cell-type plasticity and a capability of conversion under in vitro conditions. RPE cells of adult rodents [ 189 ] and human cells in vitro [ 190 , 191 , 192 , 193 ], exposed to morphogens and growth factors in the medium, demonstrate a decrease in the level of differentiation, proliferation, and, in some cases, production of neurons ( Figure 3 B). In the study by Engelgardt et al [ 189 ], RPE cells of adult rats in vitro were found to express progenitor markers: the cytoskeleton protein Nestin and the RNA-binding protein Musashi1 (Msi).…”

Cell Sources for Retinal Regeneration: Implication for Data Translation in Biomedicine of the Eye

“…The data from in vitro experiments clearly indicate the plasticity of the mammalian RPE phenotype and the potential of de- and re-differentiation, and also of reprogramming into other retinal cell phenotypes. Rodent and human RPE cells exposed to morphogens and growth factors in the culture medium lose their original properties and proliferate [ 223 , 224 , 225 , 226 ]. Adult rat RPE cells in vitro express marker proteins of neural progenitors: Nes, Musashi1, doublecortin, and β-III tubulin [ 224 ].…”