The neuroprotective effect of Müller glial cell-derived neurotrophic factors in the retina

Neuroprotection is one of the most promising strategies for the development of therapies against neurodegenerative diseases. In order to minimally disturb the delicate balance of the retina by therapeutic intervention, it is essential to identify intrinsic neuroprotective molecules and clearly elucidate their mechanisms of action in retinal tissue. Glial-Cell-Line-Derived Neurotrophic Factor (GDNF) is a powerful neuroprotective factor which enhances the survival of photoreceptors indirectly via Retinal Muller Glial cells (RMG) (Hauck et al., 2006). The indirect neuronal survival effect induced by GDNF goes through the stimulation of RMG, promoting the secretion of other neuroprotective factors which directly enhance photoreceptor (PR) survival. Unfortunately, these factors and their molecular mechanisms to prevent PR death have not been identified yet. The aim of this PhD study was to identify and validate potential neuroprotective factors secreted by RMG under GDNF stimulation and therefore validate their functional neuroprotective effect for PR survival in different animal models of retinal degenerations. In order to identify RMG derived potential neuroprotective factors, three strategies were performed. Two different transcriptomic assays were developed using GDNF-induced FACS sorted RMG and whole retinas from hGFAPeGFP transgenic mice which express GFP specifically in RMG cells. A third strategy, accomplished the identification of differentially regulated molecules following a membrane array procedure. From these approaches, the molecules presenting a denoted anti-apoptotic and/or neuroprotective activity were selected to test their functional neuroprotective effect in primary PR cultures. The tested factors which positively maintained PR survival in primary cultured PR were then applied to Pde6brd1 mouse retinal explants for short (6 days) and long terms (12 days) in culture. In addition, the supernatant from porcine RMG was injected intravitreally in Pde6brd10 mouse model of retinal degeneration in order to analyze the effect of the RMG secretome components in the maintenance of PR function in vivo.