Increased coherence of circadian rhythms in mature fibroblast cultures.

Circadian transcriptional rhythms in confluent NIH 3T3 and PER2::LUCIFERASE fibroblast cultures become more coherent as they mature. This enhanced coherence correlated with increased culture density, while inhibition of the cell cycle increased coherence in immature cultures. Mature cultures may therefore express more coherent rhythms for longer because of their reduced rate of cell division. The authors conclude that mature fibroblast cultures will be of great utility for high-throughput pharmacological and mutational circadian screening.