Abstract
Purpose :
Stargardt retinal degeneration is a monogenic maculopathy with no approved drug treatments. This disease is caused by different mutations in the ABCA4 gene. Some of the key clinical pathologies of this disease include sub or intra-cellular lipid rich deposits in the retinal pigment epithelial cells (RPE) leading to RPE and photoreceptor atrophy. Cellular phenotypes observed in patients are disruption of lysosomal activity, defective photoreceptor outer segment (POS) processing, autophagy and fatty acid oxidation in RPE cells. Metformin is a senolytic drug which has been shown to improve metabolic defects and restore lysosomal pH. We tested the in vitro efficacy of metformin in induced pluripotent stem cell (iPSC) derived ABCA4 knockouts.
Methods :
ABCA4 gene knockouts were generated using CRISPR-Cas9 technology which were differentiated to Stargardt iRPE by our lab differentiation protocol. The iRPE cells were cultured on semi-permeable membranes for five weeks to obtain a functionally mature and polarized monolayer tissue. Stargardt iRPE were subjected to physiological stressors like POS with and without Metformin (3mM). RPE morphology and functionality was assessed by microscopy and measuring transepithelial resistance (TER). The lipid deposits were stained using Bodipy dye and imaged by Confocal microscopy. RNA cell lysates were collected from mature transwells and transcriptome analysis was done using bulk RNA seq of Stargardt iRPE.
Results :
Metformin treatment for 7 days to physiologically stressed Stargardt iRPE was able to rescue sub-cellular and intra-cellular lipid accumulation measured by transepithelial resistance and lipid staining. The RNAseq analysis identified genes of the fatty acid oxidation and the lysosomal pathways to be upregulated in the Metformin treated iRPE samples.
Conclusions :
The above results demonstrate that Metformin can be used as an effective treatment for treating Stargardt retinal degeneration. The proposed mechanism of action of the drug is by targeting RPE lysosomal and fatty acid oxidation pathways.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.