Growth rate of control and beta-interferon-treated human fibroblast populations over the course of their in vitro life span.

The estimated growth rates for five lines of human fibroblasts (Human Genetic Mutant Cell Repository designations 0011, 2936B , 0038A , 2912A , and 3529), during the first few population doublings after establishment of the lines, were within the expected range, i.e., equivalent to doubling times from 16 to 28 hr, with a mean of 20 hr. The lines were derived from donors aged 8 fetal weeks, 20 days, 9 years, 26 years, and 66 years, respectively. The growth rates of the five lines declined as an exponential function of the population doubling level in all cases. The rate of decline of the growth rate varied for different lines and appeared to be related to the life span of the lines, which in turn was related to donor age. After 30 population doublings, the population doubling times had increased 1.3, 1.3, 1.7, 3.4, and 4.7 times for the five cell lines of the corresponding replicative life spans of 65, 57, 56, 31, and 28 population doublings. Sensitivity of the fibroblast lines to the cell growth-inhibitory effect of beta-interferon was independent of the population doubling level of the lines, i.e., interferon depressed the population growth rate of low population doubling level cells as much as that of middle or late population doubling level cells for any given line. However, the fibroblast lines showed differences in their sensitivity to the cell growth-inhibitory effect of interferon, probably as an expression of genotypic differences among the lines.