Noninvasive method for assessing the human circadian clock using hair follicle cells

Abstract

A thorough understanding of the circadian clock requires qualitative evaluation of circadian clock gene expression. Thus far, no simple and effective method for detecting human clock gene expression has become available. This limitation has greatly hampered our understanding of human circadian rhythm. Here we report a convenient, reliable, and less invasive method for detecting human clock gene expression using biopsy samples of hair follicle cells from the head or chin. We show that the circadian phase of clock gene expression in hair follicle cells accurately reflects that of individual behavioral rhythms, demonstrating that this strategy is appropriate for evaluating the human peripheral circadian clock. Furthermore, using this method, we indicate that rotating shift workers suffer from a serious time lag between circadian gene expression rhythms and lifestyle. Qualitative evaluation of clock gene expression in hair follicle cells, therefore, may be an effective approach for studying the human circadian clock in the clinical setting.circadian rhythm | clock gene | shift work | jet lag | chronotherapy C ircadian behavioral and physiological rhythms are driven by autonomous oscillation of clock gene expression (1-3). Thus, a clear understanding of the circadian core clock requires a thorough examination of the rhythmic expression of clock genes. As evidenced by the correlation between circadian dysfunction and the incidence of pathological diseases such as sleep disorders, metabolic syndromes, and cancer (4-7), newer strategies for monitoring clock gene expression in humans are necessary for preventing circadian rhythm-related diseases. Furthermore, medical evaluation of circadian rhythm disorders, basic research on shift work and jet lag, and chronopharmacological applications also require effective strategies for studying human clock gene expression. However, currently there is no established simple and accurate method for detecting human circadian clock gene expression. This is underscored by the fact that despite the identification of major mammalian clock genes from 1997 to 1999 (8-14), there are only about 10 studies reporting the basic research and clinical application of human clock gene expression in vivo (15,16). The lack of an established method for evaluating circadian clock gene expression has markedly impeded the progress for studying human circadian rhythms. Circadian clock gene expression is detectable not only in the central circadian pacemaker, the suprachiasmatic nucleus, but also in almost all peripheral tissues. The circadian clock is a cell-autonomous system, and numerous cell-autonomous peripheral clocks are synchronized and governed by the suprachiasmatic nucleus (17,18). These findings suggest that it is possible to characterize the human circadian clock by determining clock gene mRNA expression in peripheral tissues. In previous reports, white blood cells or oral mucosa samples were used for the detection of human clock gene expression, although these methods have several potential is...

Effects of insufficient sleep on circadian rhythmicity and expression amplitude of the human blood transcriptome

“…All three PER genes were rhythmic, confirming previous clock-gene expression data from human blood cells and hair follicles (26,27), and were confined to a small cluster with a peak close to the melatonin offset. Thus, the peripheral blood circadian clock, assessed in the absence of a sleep-wake cycle, appears to operate in concordance with what is known for other tissues.…”

Adult attention-deficit hyperactivity disorder is associated with alterations in circadian rhythms at the behavioural, endocrine and molecular levels

“…Second, alteration in circadian processes in peripheral pacemakers as noted here may not necessarily reflect changes in central processes (the key regulators of behaviour) and thus we make no claims that the oral mucosa is a proxy for the SCN. Having said this, it is worth noting that the characteristics of molecular rhythms in skin fibroblasts 25 and in hair follicles 23 do correlate with behavioural measures of the subjects from whom the samples were derived, as they do in our present study (correlations between clock gene chronometrics and actigraphic period).…”

“…19,23,24 In the present study, we developed a novel, noninvasive technique of sampling of oral mucosa for monitoring of clock gene expression. The advantage of the protocol used in this study is that it allows for selfsampling, and so does not require laboratory-based sampling and thus, when applied with actigraphy allows for a more naturalistic monitoring of circadian processes.…”

Control of skin cancer by the circadian rhythm

“…On the basis of this well-established fact, we predict that humans will have a higher rate of repair in the morning and would be less prone to the carcinogenic effect of UVR in the morning hours and it might be advisable for humans, to the extent possible, to restrict their occupational, therapeutic, recreational, and cosmetic UVR exposure to the morning hours. We note that this is a deductive conclusion based on our findings in mice reported in this paper and the evidence that humans have a robust circadian clock in their skin, which is antiphase to the mouse clock (34,35) and with the peak xpa transcript around 7:00 AM (35). However, we also note that the phase of the circadian rhythm in humans exhibits interindividual variability (different chronotypes) and that recommendations for best times for UVR exposure may have to be tailored to the various chronotypes.…”