Longitudinal study of in vivo wound repair and in vitro cellular senescence of dermal fibroblasts.

A longitudinal study was performed to confirm the inverse relationship between in vivo age and in vitro proliferative capacity previously observed in a cross-sectional study, and to investigate the relationship between the growth of dermal fibroblasts in vitro and a physiological function (i.e., wound repair) that is known to decline with age in vivo. Fibroblast cultures were generated from skin punch biopsies from 12 male hamsters beginning at 1 month of age and at 6-months interval thereafter until the natural death of the animal. All cultures from all individuals exhibited finite proliferative capacity, and an inverse relationship was observed between donor age and maximum in vitro proliferative capacity. In addition, a direct correlation between the in vitro proliferative capacity of the dermal fibroblasts in vitro and the repair efficiency of the biopsy site was observed. However, these changes in the in vitro proliferative capacity and in vivo wound repair efficiency were not progressive beyond 12-18 months of age and were not indicative at any age of an individual's ultimate lifespan. This study provides evidence that in vitro proliferative capacity of dermal fibroblasts and in vivo wound repair may be comparable phenomena that share a common mechanism. However, the nonprogressive nature and the lack of correlation between these phenomena and the individual's ultimate lifespan indicate that their use as biological markers of aging is limited to animals younger than the mean lifespan of the species.