Exploring the Effects of 1-Deoxysphingolipids on Human Macula: Insights from the Macula-on-a-Chip (MoaC) System

Abstract

Purpose : Due to the lack of effective models to study human macula, there are limited mechanistic insights and therapeutic options for complex macular diseases, such as Macular Telangiectasia type 2 (MacTel). We have developed a novel and tractable approach named Macula-on-a-Chip (MoaC) system. Here, we use and validate MoaC to mimic MacTel conditions ex vivo through elevation of 1-Deoxyspingolipids (1-deoxySL) levels, one of the main pathogenic factors of MacTel.

Methods : The MoaC system employs continuous perfusion of human retinal explants with culture medium. Macular and peripheral retinal explants from human donors were cultured for 3 days with 1-deoxySL and sphingolipids. We used TUNEL staining, LDH, NAD/NADH assays, PROTEOSTAT Aggresome Detection, bulk RNAseq and Western Blot to assess cell viability, metabolic status, protein aggregation and gene/protein expression changes. We also explored potential therapeutic interventions, including a preliminary evaluation of the rescue effect of Nicotinamide Mononucleotide (NMN).

Results : The MoaC system successfully maintained retinal structure and cellular metabolism with minimal cell death observed over 3 days' of culturing. 1-deoxySL treatment induced generalized retinal toxicity indicated by TUNEL positive cells, including Müller cells, which was significantly greater in the macula than in the peripheral retina (138% of peripheral control by LDH assay, p=0.003). RNAseq revealed the macula had different response to 1-deoxySL than the peripheral retina, with 260 versus 124 differentially expressed genes (DEGs), respectively, and only 4 shared DEGs. Notably, protein ubiquitination and NAD signaling were identified amongst the major differentially altered pathways in the macula after 1-deoxySL treatment, leading to increased protein aggregation and cell apoptosis, which were partially mitigated by NMN supplementation.

Conclusions : Our study is the first to treat the human macula with 1-deoxySL to model MacTel, revealing significant insights into the disease's pathogenesis and potential treatment avenues. The differential response of the macula to 1-deoxySL may explain its vulnerability to develop MacTel. While NMN shows promise in alleviating 1-deoxySL toxicity, further research is needed to strengthen its scientific foundation as a therapeutic option for MacTel.

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