Tauroursodeoxycholic acid (TUDCA) protects against human sub-retinal fluid toxicity in photoreceptor-enriched chick cell cultures

Abstract

Purpose: Sub-retinal fluid (SRF) that accumulates in some cases of retinal detachment is believed to be toxic to photoreceptor cells. Albumin in the SRF may play a role. In developing a model to explore this toxicity, we tested whether incubation with albumin alone or SRF from patients is toxic to photoreceptor-enriched cell cultures. As tauroursodeoxycholic acid (TUDCA) is protective in several models of photoreceptor damage and degeneration, including retinal detachment, we tested whether co-incubation with TUDCA protects against possible effects of albumin or SRF.

Methods: Human SRF was obtained from 20 patients who had surgery for rhegmatogeneous retinal detachment after informed consent approval. SRF was collected undiluted from external puncture or directly from vitrectomy via large tears. Protein concentration was measured by BCA assay. Chick photoreceptor cells were prepared from embryonic day 6 neural retinas and cultured. After 6 days in culture, bovine albumin or SRF was added to cultures. In some experiments, cells were treated with 500μM TUDCA 24h prior to addition of albumin or SRF. Cell viability was assayed 24h later using Cell Titer-Blue reagent (Promega).

Results: Incubating cells with 2.52, 12.6 and 25.5g/L albumin reduced cell viability to 58.1% ±1.5 SEM, 14.1%±0.36 and 5.2% ± 0.12 of no-albumin control, respectively (n=6-12 p<0.001). TUDCA treatment produced significantly higher cell viability (94.5% ± 5.86, 41.6% ± 3.1, and 10.5% ± 0.45 of no-albumin control) versus no-TUDCA control (p<0.001). Incubating cells with 25 or 35μL of SRF reduced cell viability to 71.6% ± 7.2 (n=2-12, p<0.001) and 26.3% ± 2.03(n= 5-12, p<0.001) of non-SRF control. Toxicity did not correlate with SRF protein concentration (r2=0.214, concentration ranged from 1.4 to 29.8g/l). TUDCA treatment produced significantly higher cell viability compared to no-TUDCA control (40.8% ±4.93 versus 26.3% ±2.03 of no-SRF control; n= 5-12, p=0.0265).

Conclusions: Bovine albumin and human sub-retinal fluid were dose-dependently toxic to photoreceptor-enriched cell cultures. TUDCA pretreatment partially reduced both toxicities. As TUDCA is well-tolerated and is approved for human use in some European countries, these findings may be of clinical interest. The first two authors contributed equally to this report.

Keywords: 615 neuroprotection • 697 retinal detachment • 694 retinal culture