Cyclic Expression of Circadian Genes in Oral Epithelial Cells

Objectives: Circadian clocks are intimately involved in controlling multiple physiologic and metabolic features on a daily basis in humans and other mammalian species. Virtually all cells in the body display peripheral clock activities that coordinate cellular processes, including cells and tissues of the immune system. Chronic inflammatory diseases, including periodontitis, may be associated with disruptions in circadian rhythm entrainment and pathway functions. The purpose of this study was to determine the circadian gene patterns in an oral epithelial cell line to establish a foundation of seminal knowledge of circadian rhythm processes.
Methods: A human oral epithelial cell line, OKF4, was grown in sub-confluent (eg. wound healing) or confluent (eg. intact barrier) monolayer cultures. qPCR with TaqMan primers (Thermo Fisher) and QuantStudio 3 were used to determine gene expression profiles at the creation of the cell cultures and with cell cycling at 8 hours, and 22hrs for CLOCK, CRY1, BMAL1, PER1, PER2, ARTNL2, NPAS2, and FOS genes.
Results: Cyclical patterns were shown in culture for BMAL1, PER1, PER2, CRY1, NPAS2 & ARTNL (sub-confluent only), FOS (confluent only). The CLOCK gene showed no cyclic pattern of expression in either confluent or sub-confluent cells. In sub-confluent cells, the FOS gene demonstrated a decreased expression over time in culture.
Conclusions: OKF4 cells were shown to express numerous circadian rhythm genes in a cyclic pattern in both confluent and sub-confluent cultures. The affected genes represented both positive and negative regulators of this pathway’s functions. The result should help develop a better mechanistic understanding of how the oral microbiome could contribute to altering healthy homeostasis of gingival tissues by altering circadian rhythm pathways that could contribute to disease outcomes. Supported by the Colgate-Palmolive Co.