ABSTRACT
Objective:To investigate the effect of circadian rhythm changes on the expression of retinoic acid-related orphan receptors (RORs) and the RORs agonist SR1078 on corneal epithelial wound repair.Methods:A total of 228 SPF C57BL/6 female mice aged 6-8 weeks old were selected, and 180 mice were divided into the normal circadian rhythm group, full-day group, full-night group, 12-hour reversed circadian rhythm group and 3-week reversed circadian rhythm group, with 36 mice in each group.The remaining 48 mice were randomly divided into phosphate buffered saline (PBS) control group and SR1078 group by random number table method, with 24 mice in each group.According to grouping, the mice were placed in a light box where the light (light intensity of 300 lx) and dark time could be controlled.The light time of the normal circadian rhythm group, the PBS control group and the SR1078 group in the light box was from 7: 00 to 19: 00, and the dark time was from 19: 00 to 7: 00 the next day.According to the Zeitgeber Time method, the starting time of light at 7: 00 was recorded as ZT0, and the time of closing light at 19: 00 was recorded as ZT12.Real-time fluorescence quantitative polymerase chain reaction was used to detect the relative expression levels of RORα and RORγ mRNA at ZT1, ZT5, ZT9, ZT13, ZT17, ZT21 in the five groups.In the PBS control group and SR1078 group, a golf-like knife was used to establish the mouse corneal epithelial injury model, and the model eyes were administered with drugs once every 6 hours according to the grouping.The corneal epithelial defect area was measured with Adobe Photoshop CC2019 software, and the corneal epithelial defect rate was calculated and compared between the two groups.The correlation between the relative expression levels of RORα and RORγ mRNA in mice corneal epithelium of the five groups and corneal epithelial defect rate in the PBS control group and SR1078 group was analyzed.The corneal epithelium repair was observed by whole cornea spreading and immunofluorescence staining, and the number of corneal epithelial dividing cells in the PBS control group and the SR1078 group was calculated and compared.The use and care of animals complied with the ARVO statement.This study protocol was approved by the Laboratory Animal Ethics Committee of Jinan University (No.JN-A-2002-01).Results:Compared with the normal circadian rhythm group, the relative expression levels of RORα/RORγ mRNA in the full-day group, full-night group, 12-hour reversed cirdian rhythym group and 3-week reversed cirdian rhythym group showed an overall decreasing trend.There was a statistically significant difference in the corneal epithelial defect rate between the PBS control group and the SR1078 group at different time points after modeling ( Fgroup=74.01, P<0.001; Ftime=5 171.48, P<0.001). Twelve hours after modeling, the corneal epithelial defect rate in the SR1078 group was significantly lower than that in the PBS control group, and the difference was statistically significant ( P<0.05). The relative expression levels of RORα and RORγ mRNA in corneal tissue was moderately positively correlated with the corneal epithelial defect rate in mice ( r=0.614, 0.537; both at P<0.01); The regression equation of the straight line between the relative expression level of RORα mRNA and the change in corneal epithelial defect rate was Y=33.153X-43.052 ( F=20.58, P<0.001), and the linear regression equation between the relative expression level of RORγ mRNA and the change of corneal epithelial defect rate was Y=2.764X-1.364 ( F=13.11, P<0.001). There was a significant overall difference in the number of corneal epithelial dividing cells at various time points following modeling between the PBS control group and the SR1078 group ( Fgroup=160.55, P<0.001; Ftime=83.57, P<0.001). The number of dividing cells in the SR1078 group was significantly less than that in the PBS control group at 24, 30, and 36 hours following modeling, and the differences were statistically significant (all at P<0.05). Conclusions:Circadian rhythm changes reduce the expression of RORα and RORγ mRNA in the mouse cornea.SR1078 can promote the expression of RORα and RORγ mRNA in corneal epithelium to decrease the number of mouse corneal epithelial dividing cells, and inhibit the repair after corneal trauma.
ABSTRACT
Objective To observe the effect of reversed circadian rhythms on wound healing of mouse corneal epithelium.Methods Ninety male C57BL/6 mice were divided into LD group (12 hours light/12 hours dark) and DL group (12 hours dark/12 hours light) by random number table,and then were placed in circadian rhythm box for 12 days.The circular area was scarped and marked as 2 mm diameter area in the center of the mouse's cornea with a golf-like knife.The dynamics of epithelial healing in the wound area were observed under microscope by fluorescein staining and hematoxylin-eosin staining.Besides,being marked antibodies of anti-Ly6G-FITC,anti-γδT-PE and DAPl,dynamic changes of the dividing cells,neutrophils and γδT cells were also investigated for every 6 hours until 42 hours.All mice were treated in accordance with the Association for Research in Vision and Ophthalmology's Statement for the Use of Animals in Ophthalmology and Vision Research and the guidelines of the Animal Experimental Committee at Jinan University (JN-A-2002-01).Results In LD group,percentage of corneal epithelial defective area were (100.000 ± 0.000) ％,(37.677 ± 5.243) ％,(14.959 ± 1.739) ％ and (0.000 ± 0.000) ％ after wounding 0 hour,6,12,18 and 24 hours.In DL group,percentage of the corneal epithelial defective area were (100.000±0.000) ％,(10.967 ± 1.065 ％) ％,(1.985 ±0.106) ％ and (0.000±0.000) ％ after wounding 0 hour,6,12,18 and 24 hours.The healing rate in DL group was higher than that in LD group,with a significant difference between them (P＜0.05).As with the uninjured corneal,thickness of corneal epithelium was (33.983 ± 1.074)μm in DL group and (33.993±0.904)μm LD group,with no statistically significant difference between them (P＞0.05).After 24 hours,thickness of corneal epithelium in DL group was (19.473 ±0.856) μm,and was more than that in LD group [(17.485±0.718)μm],with a significant difference between them (P＜0.05).Paraffin section of wounded corneal epithelium after 24 hours by hematoxylin and eosin staining showed that corneal epithelium cells arranged loosely and disorderly and were in irregular shape in both groups.The epithelium were mainly basal cells in LD group,while epithelium included basal cell and a few pinacocytes in DL group.After corneal epithelium wounded,the number of cell division,neutrophils and corneal limbus γδT cells in two groups were statistically significant difference,respectively(P＜0.05).Conclusions Reversed circadian rhythms can significantly regulate the wound healing of corneal epithelium.