Research Paper Volume 15, Issue 23 pp 13628—13645

Figure 2. Effect of donor age on repair after acute DNA damage. Primary human chondrocytes from young (n = 3, ≤45 years), middle-aged (n = 4, 50–65 years), and older (n = 3, >70 years) donors were prepared in gels on microscope slides, irradiated with 10 Gy (or not for control), and allowed to repair for various amounts of time. (A) The percentage of DNA in comet tails for all cells was averaged for each donor, and the mean of all donors per age group is shown (mean ± SEM). Repair time, age, and their interaction were significant sources of variation (2-way repeated measures ANOVA). Significant differences between groups at each time point (Tukey’s multiple comparisons test, p < 0.05) are denoted by symbols: (^*) = young vs. middle, (^#) = young vs. old, (^&) = middle vs. old. (B) The repair rate of each donor was calculated by plotting the % DNA in comet tail against repair time. The slope of the linear regression was used to define the repair rate for each donor. (C) The repair rate is plotted against age and the slope of the linear regression was significantly non-zero (p = 0.0006).