Effect of cellular aging on collagen biosynthesis: II. Collagen synthesis and deposition by a human skin fibroblast strain over 25 passages

Collagen synthesis and accumulation were studied by serial cultures of human dermal fibroblasts. A freshly seeded strain of cells was compared to cryopreserved cells from the same donor. Up to 25 passages there was no clear sign of reaching phase III, the decline of the culture. This was ascertained by the count of the dead cells floating on top of the culture fluid, the time to reach saturation density and the number of cells at confluence, counted after trypsinization. Although collagen synthesis oscillated to some extent, the average value of collagen deposited by the cells did not show any clear sign of decrease of collagen synthesis, on the contrary, there was an increase between the 15th and 25th passages. A review of the literature revealed that recent experiments on the age-dependent variation of maximal passage number did not confirm previous results showing a progressive decline, which was much delayed in recent studies as compared to previous records. The same appears to happen with collagen synthesis, found by earlier investigators to decline with increasing passage numbers. This is not confirmed, at least up to passage 25 in the present experiments. As skin tissue is progressively lost with age, our results are more in favor of increasing matrix degradation with age as an important factor of the age-dependent loss of skin tissue, more than decrease of matrix synthesis.