Assessment of circadian rhythms in humans: Comparison of real-time fibroblast reporter imaging with plasma melatonin

Sibah Hasan, Nayantara Santhi, Alpar S Lazar, Ana Slak, June Lo, Malcolm von Schantz, Simon N Archer, Jonathan D Johnston, Derk-Jan Dijk

Research output: Contribution to journalArticlepeer-review

53 Citations (Scopus)


We compared the period of the rhythm of plasma melatonin, driven by the hypothalamic circadian pacemaker, to in vitro periodicity in cultured peripheral fibroblasts to assess the effects on these rhythms of a polymorphism of PER3 (rs57875989), which is associated with sleep timing. In vitro circadian period was determined using luminometry of cultured fibroblasts, in which the expression of firefly luciferase was driven by the promoter of the circadian gene Arntl (Bmal1). The period of the melatonin rhythm was assessed in a 9-d forced desynchrony protocol, minimizing confounding effects of sleep-wake and light-dark cycles on circadian rhythmicity. In vitro periods (32 participants, 24.61±0.33 h, mean±SD) were longer than in vivo periods (31 participants, 24.16±0.17 h; P<0.0001) but did not differ between PER3 genotypes (P>0.4). Analyses of replicate in vitro assessments demonstrated that circadian period was reproducible within individuals (intraclass correlation=0.62), but in vivo and in vitro period assessments did not correlate (P>0.9). In accordance with circadian entrainment theory, in vivo period correlated with the timing of melatonin (P<0.05) at baseline and with diurnal preference (P<0.05). Individual circadian rhythms can be reliably assessed in fibroblasts but may not correlate with physiological rhythms driven by the central circadian pacemaker.

Original languageEnglish
Pages (from-to)2414-2423
Number of pages10
JournalThe FASEB Journal
Issue number6
Early online date27 Feb 2012
Publication statusPublished - Jun 2012


  • ARNTL Transcription Factors
  • Adult
  • Cells, Cultured
  • Circadian Rhythm
  • Female
  • Fibroblasts
  • Humans
  • Male
  • Melatonin
  • Minisatellite Repeats
  • Period Circadian Proteins
  • Reproducibility of Results

Cite this