Evaluation of circadian phenotypes is crucial for understanding the pathophysiology of diseases associated with disturbed biological rhythms such as circadian rhythm sleep disorders (CRSDs). We measured clock gene expression in fibroblasts from individual subjects and observed circadian rhythms in the cells (in vitro rhythms). Period length of the in vitrorhythm (in vitroperiod) was compared with the intrinsic circadian period, τ, measured under a forced desynchrony protocol (in vivoperiod) and circadian/sleep parameters evaluated by questionnaires, sleep log, and actigraphy. Although no significant correlation was observed between the in vitroand in vivoperiods, the in vitroperiod was correlated with chronotype, habitual sleep time, and preferred sleep time. Our data demonstrate that thein vitroperiod is significantly correlated with circadian/sleep preference. The findings suggest that fibroblasts from individual patients can be utilized for in vitroscreening of therapeutic agents to provide personalized therapeutic regimens for CRSD patients.
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