ANALYSIS OF GLIA CHARACTERISTICS IN THE RD10 RETINITIS PIGMENTOSA MOUSE IN COMPARISON TO THE MÜLLER GLIA DICER-CKO MOUSE, TWO MODELS OF RETINAL DEGENERATION

Abstract

"Purpose The retinal degeneration (RD) 10 mouse is a well-studied animal model that develops Retinitis Pigmentosa (RP) due to a mutation in rod photoreceptors. Müller glia (MG) are the predominant glia in the retina, have essential roles in the healthy retina, but become reactive in response to retinal damage and contribute to secondary neuronal loss. An in-depth characterization of MG in the RD mouse has not reported yet. Furthermore, molecular alterations in MG, i.e., the depletion of the enzyme Dicer1, results in photoreceptor loss resembling the phenotype of RP. Therefore, similarities in the molecular profile of MG in both models could suggest a putative common regulatory mechanism of glial alteration. The aim of this study was to characterize and compare MG in the central and peripheral retina in the RD10 mouse and the MG-specific Dicer1 conditional knock-out mouse. Methods To visualize MG in both degeneration models a MG-specific reporter mouse (Rlbp1-CreER:tdTomatostop flox/flox) was crossed with the RD10 or the Dicerflox/flox mouse (Dicer knock-out, referred to as cKO). Histological analysis was performed by means of immunofluorescence staining and confocal microscopy imaging. Retinal cross sections of 1-, 3-, and 6-months old mice were evaluated with regard to overall retinal histology, MG number and their glial protein expression pattern in both the center and periphery. Results The RD10 mouse displayed retinal thinning as early as one month of age with proliferating MG at the early phase and degenerating MG at later phases. These MG were glial fibrillary acidic protein (GFAP) positive and vimentin positive at all time points analyzed. The Dicer-cKO mouse displayed proliferating MG at early stages but not obvious degeneration was found at this time. At later stages, MG number declined in central retinal areas which were also significantly degenerated. GFAP and vimentin upregulation was not found in Dicer-cKO MG. Conclusion The MG reporter mouse is a very useful tool to study MG number and behavior in models of retinal degeneration including the RD10 mouse and the Dicer-cKO mouse. Moreover, it appears that the deletion of Dicer1 prevents MG from becoming reactive and initiating gliosis. This suggests that molecular manipulation of MG could be utilized to attenuate gliosis and subsequent degenerative events in retinal diseases."