Abstract
Purpose :
Mechanical deformations of the eye can lead to neuronal damage and, inflammation in optic neuropathies such as primary open angle glaucoma (POAG). Current treatments are limited to lowering intraocular pressure, indicating that glaucoma is fundamentally a disease of pathological mechanotransduction but the identity and properties of retinal pressure sensors are not well understood. As a step in this direction, we investigated the distribution and expression of TRPV4, a stretch-activated calcium-permeable cation channel.
Methods :
Methods Intraocular pressure (IOP) in C57BL/6 and TRPV4fl/Thy1Cre mouse retinas was elevated through the injection of magnetic microbeads. RGCs were isolated by magnetic-activated cell sorting (MACS). The cells were stimulated with cyclic biaxial strains (0.5 Hz; 1 – 15%) in the presence/absence of drugs. Immunolabeling and qRT-PCR tracked changes in gene and protein expression and localization.
Results :
TRPV4 was prominently expressed in the RGCL, where it colocalized with RGC but not amacrine markers, and the IPL, where it colocalized with dendritic markers. Glaucomatous eyes exhibited altered levels of transcripts encoding pro-inflammatory and pro-apoptotic signals including calcium-dependent calpain, caspase, and ER stress mechanisms. Similarly, mechanical stress strongly affected the expression of stress- and apoptotic signals, some of which were calcium-dependent.
Conclusions :
Prominent TRPV4 expression in the inner retina is consistent with potential functions in RGC sensing of compressive and tensile inputs in healthy and chronically hypertensive eyes. The intracellular calcium concentration in cultured RGCs is sensitive to mechanical stress, coupled with pro-apoptotic caspase and ER stress pathways, and may be influenced by TRPV4 activity. Experimental stretch and glaucoma modulate the expression of genes that encode putative stretch-activated channels in vitro and in vivo. These data show that the biomechanical milieu represents a highly effective modulatory stimulus that acts on retinal and RGC biology at the level of membrane transduction, gene expression, posttranslational regulation, and intracellular signaling.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.