Abstract
Purpose: :
RPE is a monolayer of cells underlying and supporting the neural retina. It begins as a plastic tissue, capable, in some species, of generating lens and retina, but differentiates early in development and remains normally nonproliferative throughout life. Adult human RPE cells can be activated in vitro to a self-renewing cell, the retinal pigment epithelial stem cell (RPESC) that loses RPE markers, proliferates extensively and can re-differentiate into stable cobblestone RPE monolayers. The purpose of this work is to explore whether this plasticity might explain human pathologies in which mesenchymal fates are seen in the eye.
Methods: :
RPE tissue were obtained from postmortem donors and dissected and gently dissociated in single cells. RPE cells were transferred into non adherent plates and growth as spheres and then transferred into culture plates. After 2 weeks, the cells became confluent. For clonal analysis single RPE cell was growth and expanded. To determine their plasticity, both RPE culture types were examined for their potential to form mesenchymal derivate by inductive treatments for neural, osteogenic, chondrogenic, myogenic, adipogenic lineages. RPE cells were dissociated and cultured as aggregates for 1 day and inoculated onto the CAMs chick embryos and grown for 7 days. Masses were dissected, and cryostat sectioned using mesenchymal markers for immunohistochemical analysis.
Results: :
RPE cells proliferate actively and self-renew over many passages, and they express markers associated the stem cell state. We found that under appropriate culture conditions RPE cells are highly proliferative and clonal studies demonstrate that RPESCs are multipotent and in defined conditions can generate both neural and mesenchymal progeny. This multipotency observed in human RPE can be generalized across mammalian species showed the same capabilities.
Conclusions: :
RPE can be activated in vitro to a multipotent stem cell, the RPESC, which can be expanded to produce stable RPE or readily differentiated into mesenchymal lineages. This study establishes the RPESC as an accessible, human CNS-derived multipotent stem cell can be expanded considerably even from elderly donors and could be valuable to generate stable RPE cells suitable for autologous or allogeneic replacement therapy and for producing in vitro models of RPE disease.
Keywords: retinal pigment epithelium • retinal development • retinal development