Age-related changes of distribution of S-S, S-P, and P-P division quantified from single cell expansion assays.

(A) Histogram of the proportion of CD201+CD150+KSL population (CD201+CD150+KSL cells/total cells) after 14 days culture between 6 and 52 weeks. Different color bars are corresponding to the proportion from different mice. The number of mice used in the experiment at each week of age is as follows; 4 weeks, n = 3; 5 weeks, n = 3; 6 weeks, n = 5; 7 weeks, n = 3; 8 weeks, n = 3; 9 weeks, n = 3; 15 weeks, n = 1; 20 weeks, n = 4; 22 weeks, n = 1; 48 weeks, n = 3; 52 weeks, n = 1. (B) The beta distribution of the proportion of CD201+CD150+KSL population estimated by maximum likelihood estimation at each age by Eq (1). The probabilities in 0.1 increments are shown in bar graphs. (C) The age-dependent distribution of the proportion of CD201+CD150+KSL population calculated from Eq (2). The distribution curves of CD201+CD150+KSL population change from monomodal to bimodal distributions as age increase. It suggests that S-S division is predominant in young mice whereas P-P division gradually become apparent, showing bimodal peak. Our experiments suggested asymmetric division is not predominant between 6 and 52 weeks of age.