Community Research and Development Information Service - CORDIS


STEMRD Report Summary

Project ID: 323147
Funded under: FP7-IDEAS-ERC
Country: United Kingdom

Mid-Term Report Summary - STEMRD (Generation of stem cell derived photoreceptors for the treatment and modelling of retinal degeneration)

Retinal degenerations leading to loss of photoreceptors are a major cause of untreatable blindness in the European Union. Currently no treatments restore lost photoreceptor cells and visual function, thus there is a need for new therapeutic approaches. As new photoreceptors need only make short, single synaptic connections to the inner retinal circuitry to contribute to visual function, retinal repair by photoreceptor transplantation represents one of the most feasible types of CNS repair. We have previously demonstrated that photoreceptor transplantation improves vision in a mouse model of visual dysfunction (Pearson RA et al., Nature 2012). These studies provide the first proof-of-concept for effective transplantation of neurons and provide the basis for ES cell-derived photoreceptor transplantation. The objective of this project was to determine if ES/iPS cell-derived photoreceptors could be utilised as a therapeutic source of cells to repair the degenerate retina and to model photoreceptor disorders.

So far, we have built on our achievements in the field of donor photoreceptor cell transplantation and using rod and cone photoreceptor-specific promoters driving GFP expression, we have labelled and selected pure populations of mouse ES cell-derived photoreceptors for transplantation into the adult retina. Following transplantation, we observed GFP positive photoreceptors within the host retina with cells from day 26 to 29 of culture, a stage equivalent to ~P6-8 of retinal development, showing increased efficiency. Interestingly, this was observed for both rod and cone photoreceptors, despite the cell birth of the latter cell type occurring much earlier than the former. We have further optimised the yield of ES cell-derived photoreceptors collected, by establishing ES cell lines with relevant photoreceptor-specific fluorescent reporters and have modulated the recipient retinal environment to identify optimal conditions for ES cell-derived photoreceptor survival. Although still highly variable, the number of reporter positive cells within the host retina is significantly increased compared with initial findings. Further work to investigate the functional restoration of light responses attributable to ES cell-derived transplanted cells is currently in progress using a combination of electrophysiological and behaviour tests, to determine if ES cells have the potential to provide an efficient source of functional photoreceptor precursors capable of restoring vision.

Mouse ES cell-derived photoreceptors can be generated in less than 30 days, however for human photoreceptors the differentiation process takes at least 100 days, in line with natural development. Despite this lengthy culture period we have established a robust method to generate both cone and rod human photoreceptors from both ES and iPS cells. Following transplantation, we have observed the survival of these cells in close apposition with host retinal neurons in mouse models of retinal degeneration. Further functional analysis of human ES cell-derived photoreceptors will determine if they are able to form synaptic connections and mediate light-evoked responses in the murine eye. These findings will determine the ability of human ES/iPS cell-derived photoreceptor precursors to repair the degenerate adult retina.

Finally, we have examined human ES/iPS cell-derived photoreceptor development for over 200 days, and have found that photoreceptors exhibit structural morphology, including inner segments, connecting cilia and disorganised outer segments by 190 days in culture. We have further developed our culture methods to promote timely and consistent long term retinal differentiation. This will enable the examination of photoreceptor disease phenotypes in patient iPS cell lines, which we are currently correcting by CRISPR/cas9 technology, in order to provide isogenic controls with which to evaluate this disease modelling platform.

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United Kingdom
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