Different behavior of Müller cells according to their location in the retina: possible relation with the differential susceptibility of retinal ganglion cells in glaucoma.

Abstract

Purpose : Glaucoma is a neurodegenerative disease and the leading cause of irreversible blindness in the world. Increased intraocular pressure (IOP) is considered a major risk factor. When visual problems are first detected in patients with glaucoma, half of the retinal ganglion cells (RGCs) have already died, principally in the peripheral retina. Müller glia (MG), which are the main macroglial cells in the retina, play prominent physiological and pathological roles. The change of MG to a reactive phenotype initiates signaling cascades that may serve a neuroprotective role, but may also promote damaging effects on RGCs. Our main hypothesis is that MG exert an important role in RGCs death in glaucoma, being the MG in the periphery the most sensitive to intraocular pressure, promoting the death of RGCs.

Methods : Survival of RGCs was analyzed by immunocytochemistry in porcine primary co-cultures of RGCs and MG from central and peripheral retina under control and elevated hydrostatic pressure (EHP) conditions. The conditioned media (CM) from MG primary cultures from central and peripheral retina were collected and analyzed by mass spectrometry to identify and quantify proteins in all experimental conditions.

Results : We demonstrated that in control condition MG secret neuroprotective factors, increasing the survival of RGCs (249.33 ± 47.90 RGCs/cm²) compared to RGCs growing alone (70.66 ± 1.76 RGCs/cm²) and in EHP MG contribute to RGC death (26.74 ± 2.28 RGCs/cm²). However, MG from central retina are less sensitive to EHP (65.50 ± 11.61%) since RGCs survival further decrease in co-culture with MG from peripheral retina (41.16 ± 5.28%). Moreover, stretch-activated nonselective TRPV4 cation channels present in MG are differently activated by the pressure depending of their location within the retina. Proteomic analysis from CM of MG revealed differential protein expression levels, being more pronounced in the CM from MG from peripheral retina under EHP. The proteins identified are mainly associated to apoptosis, oxidative stress, inflammation and angiogenesis.

Conclusions : The different sensitivity of the RGCs to IOP in glaucoma could be related with the different activation of neighboring MG.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.