Abstract
Purpose: :
In normal conditions, RPE remain non-proliferative throughout adult life. In lower vertebrates during retinal injury, RPE cells can re-enter the mitotic phase and produce progeny capable of regenerating all cells of the retina and in some cases also the lens. Retinal stem cells have been identified in the CE and IPR of adult rodents and human. However, until now, there has been no evidence for a stem-like cell from the adult RPE. The purpose of this work is study whether the adult human RPE retains dormant properties of early neuroepithelial cells that can be activated if removed from its normal environment.
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 neural progeny as well as mesoderm and endoderm by inductive treatments for neural, osteogenic, chondrogenic, myogenic, adipogenic and hepatic lineages
Results: :
RPE cells exhibit two characteristic morphologies: both epithelial pigmented cobblestone or fusiform with low pigmentation. These cells proliferate actively and self-renew over many passages, and they express markers associated the stem cell state, including Sox2, c-Myc and KLF4. We found that under appropriate culture conditions RPE cells are highly proliferative and are able to differentiate into an unexpectedly wide repertoire of progeny, including bone, cartilage, muscle and adipocytes, but not endoderm. We performed clonal experiments in which single primary RPE cells were clonally expanded then split into five differentiation conditions; such clonal analyses showed that RPE clones can differentiate into multiple lineages. This multipotency observed in human RPE can be generalized across mammalian species, as RPE derived from cow eyes showed the same capabilities.
Conclusions: :
This study establishes the human RPE to be a unique source of multipotent stem cells. Moreover, these cells can be obtained from patients, offering the possibility of autologous transplantation therapy. Patient-matched stem cells lines derived from RPE biopsies could be a unique source of multipotent stem cells for the study of cell fate choice and could be used to generate specific cell types for cell replacement therapy.
Keywords: retinal pigment epithelium • differentiation • plasticity