Epidermal structural changes in the SAM mouse model.

(A) Hematoxylin-eosin stained tail skin sections of senescence-resistant SAMR1 or senescence-prone SAMP1 and SAMP8 strains at 6 months of age. Scale bars: 50 μm. (B, C) Quantification of the epidermal thickness. IFE, interfollicular epidermis. The epidermal thickness is quantified from ≥6 epidermal units per mouse. N = 3. One-way ANOVA. Error bars show S.E.M. ns: not significant. (B) SAMR1 vs. SAMP1; P = 0.13. SAMR1 vs. SAMP8; P = 0.53. (C) SAMR1 vs. SAMP1; P = 0.40. SAMR1 vs. SAMP8; P = 0.79. (D) The proportion of epidermal unit harboring the micro-undulation. ≥30 epidermal units are counted in each mouse to score micro-undulations of basal regions of the IFE. N = 3. One-way ANOVA. ns: not significant. SAMR1 vs. SAMP1; P = 0.87. SAMR1 vs. SAMP8; P = 0.61. (E) Hematoxylin-eosin stained tail skin sections of senescence-resistant SAMR1, senescence-prone SAMP1 and SAMP8 stains at 1 year of age. Arrowheads indicate the micro-undulations in the basal region. Scale bars: 50 μm. (F, G) Quantification of the IFE thickness. The epidermal thickness is quantified from ≥6 epidermal units per mouse. N = 3. One-way ANOVA. ns: not significant. (F) SAMR1 vs. SAMP1; P = 0.17. SAMR1 vs. SAMP8; **; P P = 0.56. SAMR1 vs. SAMP8; P = 0.94. (H) The proportion of epidermal unit harboring the micro-undulation. ≥30 epidermal units are counted in each mouse to score micro-undulations of basal regions of the IFE. N = 3. One-way ANOVA. ns: not significant. SAMR1 vs. SAMP1; P > 0.99. SAMR1 vs. SAMP8; *; P < 0.05.