Yunxia Xue1, Peng Liu2, Hanqing Wang2, Chengju Xiao2, Cuipei Lin2, Jun Liu3, Dong Dong1, Ting Fu1, Yabing Yang2, Zhaorui Wang4, Hongwei Pan1, Jiansu Chen3, Yangqiu Li5, Dongqing Cai2, Zhijie Li6. 1. International Ocular Surface Research Center and Institute of Ophthalmology, Jinan University, Guangzhou, China. 2. Key Laboratory for Regenerative Medicine, Ministry of Education, Jinan University, Guangzhou, China. 3. International Ocular Surface Research Center and Institute of Ophthalmology, Jinan University, Guangzhou, China 2Key Laboratory for Regenerative Medicine, Ministry of Education, Jinan University, Guangzhou, China. 4. The Third People's Hospital, Puyang, Henan, China. 5. Institute of Hematology, Jinan University, Guangzhou, China. 6. International Ocular Surface Research Center and Institute of Ophthalmology, Jinan University, Guangzhou, China 2Key Laboratory for Regenerative Medicine, Ministry of Education, Jinan University, Guangzhou, China 5Section of Leukocyte Biology, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas, United States.
Abstract
Purpose: In mammalian corneal epithelium, mitosis shows a distinct circadian pattern. However, how this circadian pattern is maintained, and how it or its disruption influence renewal and regeneration remain unclear. Methods: C57BL/6 mice were maintained under 12-hour light/12-hour dark (LD), 12-hour light/12-hour light (LL), 12-hour dark/12-hour dark (DD), or reversed LD (DL, 12-hour dark/12-hour light; jet-lag defined as a shift of 12 hours) conditions. Mitotic cells in corneal epithelium were enumerated and analyzed via immunofluorescence at different zeitgeber times (ZTs). Expression of core clock genes (Clock, Bmal1, Period2, Cry1, and Rev-erbα) was qualified via quantitative RT-PCR. The rate and quality of healing at different ZT times and after administration of two small-molecule modifiers of the circadian clock, KL001 and SR8278, was evaluated. Results: In this study, photic cues were found to influence the 24-hour rhythm of corneal clock gene expression and epithelial cell mitosis in mice. Disruption of the circadian clock by exposure to constant light, constant dark, or jet-lag conditions modified the normal 24-hour patterns of corneal epithelial mitosis and corneal clock gene expression. The time of day of wound occurrence affected the rate and quality of corneal healing, with both of these parameters peaking during the more mitotically active hours of the morning. The two small-molecule modifiers of the circadian clock, KL001 and SR8278, had negative and positive effects on corneal wound healing, respectively. Conclusions: Circadian rhythms significantly influence corneal epithelium renewal and repair in mice. Our findings reveal possible opportunities for biological rhythm-based interventional strategies to control corneal healing and restore corneal homeostasis.
Purpose: In mammalian corneal epithelium, mitosis shows a distinct circadian pattern. However, how this circadian pattern is maintained, and how it or its disruption influence renewal and regeneration remain unclear. Methods: C57BL/6 mice were maintained under 12-hour light/12-hour dark (LD), 12-hour light/12-hour light (LL), 12-hour dark/12-hour dark (DD), or reversed LD (DL, 12-hour dark/12-hour light; jet-lag defined as a shift of 12 hours) conditions. Mitotic cells in corneal epithelium were enumerated and analyzed via immunofluorescence at different zeitgeber times (ZTs). Expression of core clock genes (Clock, Bmal1, Period2, Cry1, and Rev-erbα) was qualified via quantitative RT-PCR. The rate and quality of healing at different ZT times and after administration of two small-molecule modifiers of the circadian clock, KL001 and SR8278, was evaluated. Results: In this study, photic cues were found to influence the 24-hour rhythm of corneal clock gene expression and epithelial cell mitosis in mice. Disruption of the circadian clock by exposure to constant light, constant dark, or jet-lag conditions modified the normal 24-hour patterns of corneal epithelial mitosis and corneal clock gene expression. The time of day of wound occurrence affected the rate and quality of corneal healing, with both of these parameters peaking during the more mitotically active hours of the morning. The two small-molecule modifiers of the circadian clock, KL001 and SR8278, had negative and positive effects on corneal wound healing, respectively. Conclusions: Circadian rhythms significantly influence corneal epithelium renewal and repair in mice. Our findings reveal possible opportunities for biological rhythm-based interventional strategies to control corneal healing and restore corneal homeostasis.
Authors: Ericka J D Silveira; Carlos H V Nascimento Filho; Veronica Q Yujra; Liana P Webber; Rogerio M Castilho; Cristiane H Squarize Journal: Int J Mol Sci Date: 2020-01-30 Impact factor: 5.923