Mild stress culture conditions promote neurite outgrowth of retinal explants from postnatal mice

• Published in: Brain research 2020-11, Vol.1747, p.147050-147050, Article 147050
• Main Authors: Chen, Grace H., Chiao, Chuan-Chin
• Format: Article
• Language: English
• Subjects: Axon regeneration; Heat shock proteins; Heat stress; Neural activity; Osmotic stress; Retinal ganglion cells
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2020.147050

•Short-term osmotic stress and heat stress can enhance RGC neurite outgrowth from P9-P11 mouse explants.•The effect of mild stress (osmotic and heat) on RGC neurite outgrowth is largely a result of increased neural activity.•Expression of heat shock proteins 27 and 70 is correlated with the mild heat stress in promoting RGC neurite outgrowth.•These results provide significant insights into the development of therapeutic strategy for axon regeneration of RGCs. The axons of retinal ganglion cells (RGCs) in adult mammals fail to regenerate after injury. It has been suggested that some extrinsic factors, such as neural activity, may promote the regeneration process. The present study tested the hypothesis that environmental stress such as slightly elevated osmolarity and temperature can enhance neural activity and thus promote axon regeneration of RGCs in postnatal mice. Retinal explants from P9-11 mice were cultured for 5 days to study the capacity of RGC neurite outgrowth. The neural activity of retinal explants in these two stress conditions was examined using the multi-electrode array. We found that RGC neurite outgrowth from P9-P11 mouse explants was significantly enhanced when the concentration of the culture medium was increased by 1.25 fold, but not when increased by 1.5 fold. Similarly, retinal explants from P9-P11 mice grew longer neurites when the overall temperature was increased from 35 °C to 38 °C, 40 °C or 42 °C for one hour each day, but not when they were kept at 40 °C or 42 °C constantly for five days. We further showed that there was increased neural activity during these two mild stress conditions. It was found that short-term 42 °C heat stress increased the expression of heat shock proteins 27 and 70 in postnatal retinas and they were RGC neural activity dependent. The present study thus provides insights into the cellular mechanism of retinal axon regeneration under the mild stress conditions.