Abstract
Purpose :
In Zebrafish, Müller glia cells participate to the regeneration of cones when the retina is injured. Such phenomenon is believed to not occur in mammals in physiological conditions of retinal degeneration. Nonetheless, different studies have shown that Müller cells are activated in rodents after an injury and that environmental factors such as BDNF and the WNT pathway can promote some neuron regeneration, suggesting that Müller cells can undergo a transdifferentiation process. However, the formation of photoreceptors from Müller cells is limited indicating that a program of neurogenesis towards photoreceptor specification is blocked. In the present work, we studied whether Müller cells have the potential to replace photoreceptors in the mammal retina in a mouse model of inherited retinal dystrophy, the Rd1 mouse.
Methods :
Mice expressing the DsRed protein driven by the GLAST promoter to label glial cells were crossed with Rd1 mice. Mice expressing Cre recombinase under the activation of the GFAP promoter were crossed with Z/EG-GFP mice which express GFP only after the excision of the flox sequences. Then this double transgenic was crossed with Rd1 mice to obtain the GFAP::Cre;Z/EG-GFP;Rd1 line. Immunohistochemistry for glial, progenitor and photoreceptor markers was performed at different time points of the degeneration.
Results :
In WT retina, P27 staining is located in the INL and in the Müller cells, and Pax6 in several interneurons as well in RGCs. In the Rd1 retina, we observed rare Pax6-positive cells in the ONL at the vicinity of the INL during the degenerative process. Migration of some GLAST::dsRED cells towards the ONL is also observed. To better follow the Müller cell behavior, we analyzed retinas of GFAP::Cre;Z/EG-GFP mice. At PN10, GFP is exclusively localized in Müller cells of WT and Rd1 retina. At PN28, in the WT retina several Müller cells are GFP-positive (not all) and, at the outer extremity of these cells in the ONL, a few GFP-positive photoreceptors were detected (5+/-0.7 cells/100 um). In Pde6b+/- mice, many more Müller cells are positive for GFP and 5 times more GFP-photoreceptors were counted (17+/-2 cells/100 um). PN12 and PN13 Rd1 retinas are under analyses.
Conclusions :
These results suggest that under physiological stimulations a subset of Müller cells can reactivate a program of neurogenesis to generate photoreceptors during the perinatal period at least.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.