Fig. 1

Assembly and construction of scRNA-seq atlas of muscles from young, old and frail mice. (a) Schematic diagram of frailty assessments of young (n = 9) and old (n = 55) mice. NF-Y, 7.5-month-old (young) non-frail mice; NF-O, 24.5-month-old (old) non-frail mice; PF-Y, 7.5-month-old (young) pre-frail mice; PF-O, 24.5-month-old (old) pre-frail mice; F-O, 24.5-month-old (old) frail mice. The figure was partly generated using Servier Medical Art, provided by Servier, licensed under a Creative Commons Attribution 4.0 unported license. (b) The prevalence of frailty in young and old mice. Frailty status was based on the cutoff values for each criterion in each respective age. (c) Graphic representation of frailty index values in non-frail, pre-frail, and frail groups between young and old mice. Data are presented as mean ± SD. Statistical differences were tested using the t-test for two groups or one-way ANOVA for three groups. (d-h) Percentage of success in the unintentional weight loss (d), tight-rope test (e), running time (f), running speed (g) and grip strength (h) of NF-Y (n = 6), NF-O (n = 6), and F-O (n = 9). Statistical differences were tested using Pearson’s chi-squared test. (i) Hematoxylin and eosin (H&E) staining was used in each group to assess the tissular integrity of muscle samples. Scale bar, 50 μm. (j) The distribution of myofiber sizes determined using the minimum Feret diameter was quantified for each group. (k) The fiber cross-sectional area (CSA) of each group was assessed. Statistical differences were tested using one-way ANOVA for three groups.