Abstract
Purpose: :
To compare the effect of the transcription factor Crx on the differentiation of human adult corneal and retinal stem cells .
Methods: :
Stem cells isolated from post-mortem cornea and retinal ciliary body were maintained in serum-free culture, and genetically modified by electroporation to express exogenous epitope-tagged murine Crx. Changes in the expression of stem cell markers (homeodomain transcription factor Pax6, POU transcription factor Oct3/4, proliferating cell nuclear antigen), neuronal markers (nestin, neuron-specific class III ß-tubulin and neurofilament), and photoreceptor-specific markers (rhodopsin, cyclic nucleotide-gated cation channel-3, blue-cone opsin, cyclic (c)GMP phosphodiesterase) expression were evaluated by immunocytochemistry. Photo-transduction cascade activity was assessed by measuring light-induced hydrolysis of cGMP levels using a cGMP enzyme-linked immunoassay.
Results: :
Expression of stem cell markers of proliferation and pluripotency was decreased by exogenous Crx expression in both human corneal and retinal stem cells. Concomitantly, expression of neuronal and photoreceptor-specific markers was increased. Both corneal and retinal stem cells differentiated into cells of photoreceptor phenotype, but only the genetically-modified retina-derived stem cells displayed light-induced cGMP hydrolysis characteristic of a fully-functioning visual phototransduction cascade.
Conclusions: :
The present study extends our previous findings that exogenous Crx expression can promote differentiation of human retina-derived stem cells into functional photoreceptor phenotypes (Jomary and Jones, 2008). Although Crx can induce human cornea-derived stem cells to express photoreceptor-specific proteins, it does not seem to be sufficient to direct their differentiation into functional photoreceptors. Others transcription factors are probably needed to achieve this goal. Nevertheless, this study lends support to the notion that genetic modification of adult human ocular stem cells can be used to direct their differentiation into a photoreceptor phenotype.
Keywords: retina • transcription factors • differentiation