Adult human retinal pigment epithelial cells capable of differentiating into neurons

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Abstract

We investigated the ability of adult human RPE cells to differentiate into neurons. Two cell lines were evaluated. The cells were cultured in medium with 8% serum, transferred to a neural stem cell maintenance culture, and induced to differentiate with retinoic acid. The cells were immunocytochemically examined at each step. The cells showed epithelial-like morphology with 8% serum and all were immunoreactive for β-III tubulin. After transfer to the stem cell maintenance culture, they changed morphologically and became immunoreactive for MAP5 and neurofilament200 after inducement with retinoic acid. The ratio of MAP5 positive cells was higher in the young adult RPE cell line. No GFAP or rod-opsin immunoreactive cells were observed. Adult human RPE cells even from old person are capable of differentiating into neurons, although the ratio of mature neurons was greater in the young than in the old cell line in this condition.

Section snippets

Human retinal pigment stem cells

Two human adult retinal pigment epithelial cell lines were used in this study, H80HrPE (80-year-old human differentiated pigmented epithelial cells)-6 and ARPE-19.

H80HrPE-6 was established by Eguchi et al. and harvested from the eye bank eye of an 80-year-old male, while ARPE-19 was harvested from a young eye.

Establishment of the human RPE cell clone

Eyecups were made from the eye, after which the neural retina was removed from the eye cups and placed in PBS. The eyecups were incubated in 0.05% EDTA, and only then the pigmented

Characteristics of human retinal pigment cell line

H80HrPE-6 cells and ARPE19 cells showed a flat and polygonal epithelial-like morphology without pigment in epithelial culture medium with fetal bovine serum (Fig. 1A). They had remained healthy after freezing and thawing. Cells of either line contained no visible pigment until after 5 months’ culture, when some cells of ARPE19 showed visible pigment in their cytoplasm.

The cells cultured for 2 weeks in the epithelial culture medium were examined immunocytochemically. Most of the cells showed

Discussion

The RPE cells of many vertebrate species can dedifferentiate and transdifferentiate in response to changes in their environment. It is well known that in amphibians RPE cells transdifferentiate not only into lens cells, but also into retinal neurons [10], [11], [16]. It was reported that growth factors and extracellular matrix components are found to be important in the control of the transdifferentiation process of vertebrate pigmented epithelial cells [15].

In embryonic rat, RPE cells were

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