Valosin-Containing Protein Inhibition: Neuroprotective Strategy Against Retinal Degeneration in Porcine and Human Models.

Abstract

Purpose : We previously identified that inhibition of valosin-containing protein (VCP) prevents photoreceptor (PR) degeneration in rodent models of retinitis pigmentosa by mitigating endoplasmic reticulum (ER) stress and enhancing energy homeostasis. Given the intricate connection between oxidative stress and ER stress in retinal degeneration, our investigation extended to assessing the impact of VCP inhibition in cone-rich porcine retinal explants co-cultured with human iPSC-RPE cells, with and without inducing oxidative stress, and further examined human retinal explants to evaluate neuroretinal protection of PRs and potential drug-induced toxicity.

Methods : Retinal explants obtained from the cone-rich visual streak of adult porcine eyes, in combination with human iPCS-RPE cells, and explants from two human donor eyes enucleated for uveal melanoma removal, were cultured in a medium-air interphase under serum-free conditions for up to 8 days. Inhibition of VCP was achieved using ML240. In the porcine retina, oxidative stress was induced using hydroquinone (HQ) alone or in combination with ML240. Rhodopsin, iba-1, cone opsin, and cone arrestin immunostaining, along with TUNEL assay were used to assess retinal morphology, cell death, and cone PR survival.

Results : In the porcine retina, treatment with HQ resulted in a reduction of nuclei rows in the outer retina, shortening of PR outer segments and decrease in the number of cone PRs. VCP inhibition by ML240 protected against HQ induced cone PR degeneration. Moreover, VCP inhibition in human retinal explants showed a trend toward more cone PRs and longer outer segments in the ML240 treated retinas. Equally important, ML240 treatment exhibited no signs of cytotoxicity after 8 days in vitro and we observed decreased microglia cell activation and -migration to the outer retina, indicating a reduction of inflammation compared to the vehicle control.

Conclusions : Pharmacological VCP inhibition demonstrates a protective effect on on cone photoreceptors, shielding them from degeneration induced by hydroquinone in a co-culture model of porcine retinal explants/iPSC-RPE cells as well as in human retinal organotypic cultures. The observed neuroprotection, combined with the absence of any detectable cytotoxic side effects provides compelling support for exploring VCP inhibition as a prospective therapeutic strategy for human retinal disorders.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.