Calorie restriction enhances adult mouse lung stem cells function and reverses several ageing-induced changes.

Ageing is associated with decreased lung function and an increased incidence of lung infections. Several studies have suggested that long-term calorie restriction (CR) promotes health and longevity and results in the reduced risk of several diseases. The effect of CR is thought to be through improving the function of tissue stem cells. Stem cell function is known to decline with ageing. In this study, we examined the effects of ageing on lung epithelial and stem cells and the effect of CR on young and old lungs. We found that ageing results in a decrease in tracheal basal stem cells. CR induced an increase in basal stem cells in both young and old mice. In addition, ageing induced lung inflammation, and CR tended to reduce baseline lung inflammatory cell infiltration in young mice and significantly reduced ageing-induced lung inflammation. Furthermore, ageing reduced the number and function of mitochondria in lung and increased the level of mitochondrial reactive oxygen species. CR increased the number and function of mitochondria both in young and old mice. Moreover, ageing reduced lung stem cell colony-forming efficiency (CFE), and CR increased the CFE in both young and old mice. Finally, CR improved epithelial cell survival in injured lungs of young mice. In conclusion, ageing causes several structural and functional changes/impairments in lung epithelial cells. CR induces several potentially beneficial changes in lung epithelial cells, even when it is initiated at an older age, including reversal of some ageing-induced changes.