Abstract
Purpose :
Despite being crucial to neuronal survival, the role of Müller cells (MC) in geographic atrophy (GA) has only recently been considered. We have shown MC extending into the subretinal space in GA and in the rat subretinal sodium iodate (SI) model. However, the consequences of these events remain unclear. We investigated whether MC retain their normal functional profile or form a fibrotic scar in both human GA eyes and the SI model.
Methods :
Sprague Dawley rats were given subretinal injection of SI (5mg/ml) and were sacrificed at 3, 8 and 12 weeks (wks). Cryosections from these rats and human GA donor eyes were stained with antibodies against MC homeostatic proteins; Glutamine synthetase (GS), Aquaporin4 (AQP4), Cellular retinaldehyde–binding protein (CRALBP), S100 calcium binding protein B (S100B), Inwardly Rectifying Potassium Channel (Kir4.1) and activation marker, glial fibrillary acidic protein (GFAP). Additional staining utilized fibrosis markers: α-smooth muscle actin, fibronectin, collagen 4, and 1. Images were captured on a Zeiss 710 confocal microscope.
Results :
MC at the border had increased GFAP expression with a corresponding reduction in GS in both human GA donor eyes and SI-injected rats. While GS expression in the atrophic area was diminished, it was prominently expressed in the subretinal glial membrane. In control, MC expressed AQP4 at the endfeet and around retinal blood vessels. However, in both SI-injected and human GA eyes, AQP4 was expressed throughout the entire length of the MC at the atrophic border and within the membrane. We observed GFAP+ and AQP4+ MC process breaching the Bruch’s membrane at 12 wks post-SI injection. Kir4.1 expression significantly reduced in the atrophic area but was notably higher in the subretinal space. AQP4 and Kir 4.1 surrounding GS-isolectin+ blood vessels was reduced at 12 wks. MC radial processes in both SI-injected and GA eyes showed increased S100B expression compared to non-atrophic area and control. CRALBP expression remained unaltered. Glial cells in the subretinal membrane of both GA eyes and the SI model did not express fibrotic markers.
Conclusions :
Our findings highlight the persistence of homeostatic proteins in MC within the subretinal space, rather than the formation of a fibrotic scar, in both GA and a rat model. The altered expression of these proteins suggests disruption of polarity or mislocalization in MC associated with atrophy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.