Circadian Rhythms in Murine Ocular Tissues including Sclera are affected by Neurobasal A Medium Preincubation, Mouse Strain, but not Sex
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Purpose
Our understanding of ocular clocks has been profoundly advanced by the development of real-time recording of bioluminescence of PER2::LUC knock-in mouse explants. However, the effect of sex, mouse strain and culturing conditions on ocular clocks remains unknown. Here, we studied the role these variables play on PER2::LUC bioluminescence rhythms of ocular tissues: retinas, corneas and posterior eye cups (PEC). We also tested the hypothesis that the sclera contains a circadian oscillator by using scraped PEC as a proxy.
Methods
Retinas, corneas, intact and scraped PECs were obtained from male and female PER2::LUC knock-in mice maintained on either a pigmented C57BL/6J or albino RjOrl:SWISS background. PER2::LUC bioluminescence rhythms in ocular tissues were measured using a Lumicycle®.
Results
We compared PER2::LUC bioluminescence rhythms between ocular tissues and found that all ocular tissues oscillated, including the scraped PEC, which was previously not known to oscillate. The rhythms in scraped PECs had lower amplitudes, longer periods and distinct acrophases compared to other ocular tissues. Ocular tissues of RjOrl:SWISS mice oscillated with higher amplitudes compared to the ones of C57BL/6J, with corneal rhythms being most affected by mouse strain. A 24h preincubation with Neurobasal A medium enhanced rhythms of ocular tissues, whereas sex differences were not detected for these rhythms.
Conclusions
We discovered a novel oscillator in the sclera. PER2::LUC bioluminescence rhythms in murine ocular tissues are enhanced by Neurobasal A medium preincubation, mouse strain but not sex.
