Age-related response of human dermal fibroblasts to L-ascorbic acid: study of type I and III collagen synthesis.

Stimulation of the synthesis of type I and III collagens by 0.15 mM L-ascorbic acid (AA) was investigated in primary cultures of dermal fibroblasts form 30 females aged between 19 and 70 years. At this concentration allowing maximal stimulation, fibroblast cultures responded to this agent by an increase in collagen secretion, but to a lower extent for type III compared to type I, leading to an increase in the type I/III collagen ratio. We showed that AA stimulation of type I and III collagen secretion decreased in a statistically significant linear manner with donor age (slope = 1.9; p = 0.0014 and slope = -0.5; p = 0.0164, respectively). We also observed an age-related AA stimulation of the cell-associated collagen pool for type I collagen but not for type III (slope = 0.29; p = 0.015). This might indicate that a reduced ability of fibroblasts to secrete the newly synthesized type I collagen is involved in loss of the cellular response to AA stimulation. Analysis of AA stimulation as a function of body site showed that during aging, the loss of AA stimulation of type I and III collagen synthesis was more for periauricular (slope = 2.7; p = 0.0280 and slope = -0.8; p = 0.0309, respectively) than for mammary skin (slope = 2.1; p = 0.0071 and slope = 0.1; p = 0.7337, respectively). This led us to consider that UV-exposed cutaneous sites may accelerate cellular dermal aging in terms of response to AA, making this parameter a quantitative indicator of human dermal cell aging.