Fig. 9: Aged MGs exhibit reduced peripheral innervation and collagen I expression.

a GO analysis of genes with statistically significantly reduced expression in aged compared with young acinar basal cells (cluster #16). b Violin plots for neuronal guidance genes in acinar basal cells. c, d)Slit3 mRNA expression (yellow arrows) is reduced in aged MG acinar basal cells. e, f GO analysis of genes with reduced expression in aged cluster #23 dermal cells (e) and violin plots for neuronal guidance genes (f). g, h Reduced numbers of PGP9.5 nerve fibers (red) adjacent to the KRT5⁺ acinar basal layer (green) in aged mice. i Quantification of PGP9.5⁺ nerve fibers within 5 μM of each KRT5⁺ acinar basal cell in young and aged MGs. Independent biological samples from n = 4 8-week-old and n = 4 21-month-old male C57BL/6 J mice were used for quantification. At least 185 acinar basal cells were analyzed from each mouse. Significance in (i) was calculated by an unpaired two-tailed Student’s t-test. Data are represented as mean +/− SEM. Source Data are provided as a Source Data file. j, k GO analysis of genes with reduced expression in aged cluster #15 dermal fibroblasts (j) and violin plots for type I collagen genes in dermal fibroblasts (k). l, m Reduced expression of Col1a1 (red) in aged (m) versus young (l) dermis surrounding MG acini. For (a, e, j) FDR calculation was performed by clusterProfiler (v4.4.4) and EdgeR (v3.38.4) with the Benjamini-Hochberg procedure. Dot plots in (a, e, j) were generated with ggplot2. Violin plots in (b, f, k) were generated with the VlnPlot command from Seurat package. White dashed lines in (c, d, l, m) outline MG acini and/or ducts. Independent biological samples from n = 3 8-week and n = 3 21-month C57BL6/J mice were used for RNAscope, IF and IHC. Scale bars represent 25 μm. See also Supplementary Fig. S7.