Abstract
Purpose :
The loss of photoreceptor cells is a hallmark of retinal degeneration. Primary cultures of embryonic chick retinal cells (ECRCs) enriched for photoreceptors are a well-known model for studying the biochemistry of photoreceptors. Circadian rhythms in ECRCs can be reset by light exposure[JB1] . Whether this sensitivity to light extends to induction of cell death is unknown. The purpose of this project was to test the hypotheses that, similar to in vivo models of LIRD, light exposure can induce cell death in ECRCs and this death can be prevented by treatment with neuroprotective compounds.
Methods :
Undifferentiated retinocytes from 7-day chicken embryos were grown under conditions promoting development of cone cell characteristics[JB1] . After 3 days, cells were exposed to varying intensities of light (2,500-10,000 lux) for varying amounts of time (2-24 h). In other experiments, cells were pre-treated for 2 h with xanthohumol (Xn; 0.1-10 µM) or tauroursodeoxycholic acid (TUDCA; 500 µM), both of which protect against LIRD in mice. To determine if light exposure was specifically toxic to ECRCs, some iterations of the experiments included separate cultures of fibroblasts that were harvested from the same embryos.
Results :
Exposure to 2,500 lux for 24 h caused a 70% decrease in viability (p < 0.05), determined as a function of fluorescence emission by live cells. Exposure to 10,000 lux significantly reduced cell viability at all time points, and viability decreased with increasing exposure duration. Fibroblasts did not exhibit toxicity following light exposure. Pretreatment of ECRCs with TUDCA or Xn protected against light-induced cell death (p < 0.05).
Conclusions :
Cultures of ECRCs, but not fibroblasts, undergo light-induced cell death in a dose-dependent manner, similar to in vivo models of LIRD. Also similar to in vivo LIRD models, the death of ECRCs is prevented by treatment with TUDCA or Xn. Thus, we have described a new, easily-reproduced model that allows for direct observation of the events leading to light-induced photoreceptor death. This LIRD model may serve as a fast, inexpensive and practical alternative to whole animal models, or may be used as a guide for later in vivo studies. This model may also aid in the screening of compounds that are hypothesized to prevent or attenuate photoreceptor loss.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.