Fig. 1

Heterochronic fecal microbiota transfer affects spermatogenesis of young and old mice. A The experimental workflow for fecal microbiota transplantation (FMT) and multi-omics examination of young (6-week), old (18–20-month), and FMT mice. For FMT groups, y FMT y and o FMT y (damaged comparison) indicate young mice received young or old donor microbiota, respectively; o FMT o and y FMT o (rescued comparison) indicate old mice received old or young donor microbiota, respectively. B–D Sperm quality including sperm concentration (B), progressive motility (grade A + B sperm) (C), and total motility (grade A + B + C sperm) (D). E–L Representative images of H&E staining (E, F, I, J) and immunofluorescence staining of testis tissues (G, H, K, L) for FMT mice. DAZL (spermatogonia marker), SYCP3 (spermatocyte marker), TNP1 (spermatid marker), PGK2 (spermatozoa marker), and WT1 (Sertoli cell marker) were stained. Scale bar = 100 μm for E, F, I, J or 25 μm for G, H, K, L. All data are presented as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001. Data are analyzed by two-tailed unpaired Student’s t test. n = 7–8 mice per group