Retinal ganglion cell regeneration for retinal repair
Müller glia-dependent regeneration of retinal ganglion cells
This research aims to test the hypothesis that retinal ganglion cell death stimulates “Müller glia” dedifferentiation into a population of proliferating retinal progenitors that can regenerate lost retinal ganglion cells. We propose to use zebrafish in these studies because of their robust regenerative powers. Our approach is to first generate a transgenic zebrafish model of retinal ganglion cell death, similar to that which occurs during glaucoma, and then investigate if Müller glia can regenerate these damaged cells.
My lab is interested in identifying strategies for repairing the diseased and injured retina. We are focusing on endogenous mechanisms of retinal repair and are investigating if Müller glia, which are resident to the retina, can be coaxed to regenerate damaged retinal ganglion cells. If we can stimulate Müller glia to regenerate retinal ganglion cells it may provide a means for restoring retinal ganglion cell function in diseases like glaucoma. We use zebrafish as a model system for these studies because they exhibit a very robust regenerative response to retinal injury which helps in identifying mechanisms underlying successful regeneration. Although we know that Müller glia can function as retinal stem cells following injury, no one has tested whether damage specifically targeted to retinal ganglion cells, as occurs in glaucoma, is sufficient to stimulate Müller glia-dependent retinal ganglion cell regeneration. We propose to develop a new zebrafish model to test this idea and then use this model to uncover the molecular mechanisms underlying Müller glia-dependent retinal ganglion cell regeneration. We anticipate that these mechanisms will suggest novel strategies for stimulating Müller glia to repair damaged retinal ganglion cells following injury or disease of the human retina.
Dr. Goldman’s team has generated transgenic zebrafish models that allow them to conditionally ablate (destroy) retinal ganglion cells in adult animals and may serve as models of glaucoma. The team has also discovered that they can use the growth factor protein, called HB-EGF, to stimulate Müller glia to change into a retinal stem cell that can regenerate all types of retina cells. These studies provide novel models and approaches for understanding the mechanisms by which diseased or damaged retinal neurons can be restored. These studies may suggest novel strategies for stimulating retinal repair in humans following injury or disease.
One aim in the team’s proposal was to generate transgenic fish harboring the bacterial nitroreductase gene under control of the retinal ganglion cell-specific promoter, Pou4f3. The expression of nitroreductase causes a toxin to be created that conditionally ablates the retinal ganglion cells in which the protein is present. Nitroreductase on its own has no effect on cells, however, when the cells are exposed to metronidazole, the nitroreductase is converted into a cytotoxic product. Dr. Goldman’s team has successfully generated these fish, which are anticipated to serve as a model for glaucoma-induced retinal ganglion cell death.
In addition, the team has generated another type of fish with a gene that has the tuba1a promoter driving expression of bacterial nitroreductase. Unlike the Pou4f3 fish that constitutively (continually) express nitroreductase in retinal ganglion cells, the tuba1a fish only express this protein after their optic nerve has been damaged. Both lines of fish are now being raised to adults to examine if adult Müller glia can regenerate ablated retinal ganglion cells. If successful, this team could provide a new treatment option for glaucoma.
Wan, J., Ramachandran, R. and Goldman, D. HB-EGF is necessary and sufficient for Muller glia dedifferentiation and retina regeneration. Dev Cell, 2012; 22:334-347.
First published on: April 1, 2010
Last modified on: March 19, 2013