Clock gene expression in human and mouse hepatic models shows similar periodicity but different dynamics of variation

Gianluigi Mazzoccoli, Rosa Rubino, Cristiana Tiberio, Francesco Giuliani, Manlio Vinciguerra, Jude Oben, Angelo De Cata, Roberto Tarquini, Salvatore De Cosmo, Shu Liu, Yanning Cai

Research output: Contribution to journalArticle

Abstract

The biological hard-wiring of 24-hour rhythmicity relies on the circadian clock circuitry, made of peripheral oscillators operated by molecular clockworks and synchronized through humoral and neural outputs by central oscillators located in the hypothalamic suprachiasmatic nuclei. Metabolically active tissues, such as the liver, are entrained also by local cues represented by metabolic flux related to feeding. The mechanics of the molecular clockwork have been explored by studies using cell lines and wild type or genetically engineered mouse models. There is a compelling need to reduce the use of animals in experimental settings. The aim of our study was to evaluate the periodicity and dynamics of functioning of the hepatic clock gene machinery in human and mouse hepatic models. We compared the results obtained in human hepatoma cells (HepG2 cells) and in mouse liver, and a significant 24-hour rhythmic component was found for five clock genes in the HepG2 cells (Bmal1, Cry1, Per1, Per2, NR1D1) and for six clock genes in the mouse liver (Bmal1, Clock, Cry1, Per1, Per2, NR1D1). The amplitude of oscillation rendered by the cosine curve and the dynamics of expression rendered by the rate of change (the derivative of gene expression level with respect to time) were greater in the mouse liver than in the HepG2 cells for Bmal1, Per1, Per2 and NR1D1, and the cosine curve phase was different for many of them. In conclusion, the periodicity of expression of the clock genes showed similar patterns when the two experimental models were compared, whereas the dynamics of transcription in human hepatoma cells cultured in vitro were less vigorous and phased in a different way when compared to mouse hepatic tissue. The results support the reliability of the human hepatic in vitro model as an alternative to animal models only to study the periodicity of function of the molecular clockwork, but not to evaluate the dynamics of clock gene expression.

Original languageEnglish
Pages (from-to)181-190
Number of pages10
JournalChronobiology International
Volume33
Issue number2
DOIs
Publication statusPublished - Feb 7 2016

Keywords

  • Chronobiology
  • clock genes
  • hepatocytes
  • liver

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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