Human molecular circadian rhythms and ageing

Abstract

Purpose: Validation of an approach to study human circadian rhythms in vitro and investigation of the effect of ageing on period length in this model. Methods: In vitro circadian rhythms were obtained by infecting skin fibroblasts from different donors (10 sighted, 8 blind, 18 young, 18 older) with a lentivirus mBmal-1::luc. Measurements were conducted under standard experimental conditions (bovine serum) or in human serum-containing medium. In vivo circadian period length was additionally analysed in sighted and blind subjects. Results: A good correlation was observed between in vitro and in vivo period length of both sighted and blind people. Between young and older sex-matched subjects no change of the circadian period length of fibroblasts was found under standard experimental conditions. Of note, when human fibroblasts were measured in human serum-containing medium a reduction in period length was found only for cells treated with „older“ serum. Heat-inactivation of sera from older donors almost undid the reduction in the period length suggesting that protein/s is/are responsible for the circadian disturbances observed in the elderly. Conclusions: Fibroblasts are a good model to study circadian rhythms in vitro. The interplay between the molecular components of the skin fibroblasts oscillators does not change during ageing in general. However, the age-related changes in circadian rhythms in vivo and/or in vitro are possibly related to still unknown circulating factors.