Neurosphere from adult stem cells, stained with the glial marker GFAP

Isolation, culture and differentiation of adult stem cells
Stem/progenitor cells that give rise to neurons and glia have been identified in several regions of the central nervous system, including the embryonic retina and the ciliary epithelium of the adult eye, raising the possibility of autologous transplantation. We have shown the presence of stem/progenitor cells in additional regions of the porcine eye including the pars plana and iris, regions that, in the human, are readily accessible during routine eye surgery. When cultured in the presence of growth factors, these cells proliferate to form neurospheres comprised of cells expressing retinal stem/progenitor markers.

Using an adherent monolayer culture system, these cells could be readily expanded to increase their number more than a million-fold, while maintaining a progenitor phenotype. Another source of potential progenitor cells is the sub-ventricular zone in the brain, although this source would not be usable for autologous transplants as it is not available for sampling during routine procedures.
Before transplantation into the eye, these cells need to be differentiated to a developmental stage that allows them to integrate into and connect with the neuroretina, similar to the immature photoreceptor cells mentioned before. A promising strategy for directing the differentiation of a population of progenitor cells is to utilise viral gene transfer to express key transcription factors. Studies using rat and primate iris tissue have been successful in generating cells with a photoreceptor like phenotype following transduction with Crx and Crx/Nrl, respectively. Further studies will be needed to establish if similar techniques may be used to guide the differentiation of iris, ciliary body and pars plana stem/progenitor cells that have undergone multiple passages and expansion in tissue culture. Ideally, by using gene transfer, the appropriate combination of factors could be delivered to generate functional photoreceptor precursor cells with the potential for integration into a recipient retina.

Introduction

Retinal repair by transplantation of photoreceptor precursors

This page last modified 18 December, 2012 by xxx