A detection method for latent circadian rhythm sleep-wake disorder.

BACKGROUND: Individuals with typical circadian rhythm sleep-wake disorders (CRSWDs) have a habitual sleep timing that is desynchronized from social time schedules. However, it is possible to willfully force synchronisation against circadian-driven sleepiness, which causes other sleep problems. This pathology is distinguishable from typical CRSWDs and is referred to here as latent CRSWD (LCRSWD). Conventional diagnostic methods for typical CRSWDs are insufficient for detecting LCRSWD because sufferers have an apparently normal habitual sleep timing. METHODS: We first evaluated the reliability of circadian phase estimation based on clock gene expression using hair follicles collected at three time points without sleep interruption. Next, to identify detection criteria for LCRSWD, we compared circadian and sleep parameters according to estimated circadian phases, at the group and individual level, between subjects with low and high Pittsburgh Sleep Quality Index (PSQI) scores. To validate the reliability of identified detection criteria, we investigated whether the same subjects could be reproducibly identified at a later date and whether circadian amelioration resulted in sleep improvement. FINDINGS: We successfully validated the reliability of circadian phase estimation at three time points and identified potential detection criteria for individuals with LCRSWD attributed to delayed circadian-driven sleepiness. In particular, a criterion based on the interval between the times of the estimated circadian phase of clock gene expression and getting out of bed on work or school days was promising. We also successfully confirmed the reproducibility of candidate screening and sleep improvement by circadian amelioration, supporting the reliability of the detection criteria. INTERPRETATION: Although several limitations remain, our present study demonstrates a promising prototype of a detection method for LCRSWD attributed to delayed circadian-driven sleepiness. More extensive trials are needed to further validate this method. FUNDING: This study was supported mainly by JSPS, Japan.

Ex vivo Culture Assay Using Human Hair Follicles to Study Circadian Characteristics.

Ex vivo culture assays of biopsy specimens are advantageous for the experimental evaluation of human circadian characteristics. We developed a simple and non-invasive experimental evaluation method for monitoring the expression of circadian clock genes in an ex vivo culture assay using human hair follicles. This method imposes little burden on subjects. This assay is useful for validating correlations between circadian characteristics in hair follicles and intrinsic characteristics observed in physiological and behavioral studies. While they should be further validated, this ex vivo method constitutes a useful tool for estimating in vivo circadian characteristics.

A Method for Culturing Mouse Whisker Follicles to Study Circadian Rhythms ex vivo.

Ex vivo tissue-culture experiments are often performed in the field of circadian biology. The major aim of these experiments is to evaluate circadian characteristics such as period length at the tissue-autonomous level by monitoring clock gene expression in real time. This culture method is also used to examine the tissue specificity of circadian entrainment factors. However, an ex vivo culture method for monitoring clock gene expression in hair follicles has yet to be established. In the present study, we developed an experimental method to analogize and evaluate circadian characteristics by performing ex vivo culture of mouse whisker follicles and monitoring clock gene expression in real time.