Extended Data Fig. 7: Restoration of SAM is associated with improved muscle regeneration and function of aged mice.
From: Depletion of SAM leading to loss of heterochromatin drives muscle stem cell ageing
a, MuSCs were isolated from the injured muscles of female mice at 2 days post injury (dpi). (Left) Representative confocal images. (Scale bar, 5 μm) (Right) The ratio of γ-H2AX foci per cell was quantified (n = 4 for young mice, and old mice treated with vehicle or SAM, n = 3 for old mice treated with MCHA). b, (Left) Representative TUNEL assay images of female MuSCs isolated at 2dpi (Scale bar, 50 μm). (Right) The ratio of apoptotic cells over total cells was quantified (n = 4 for young mice, and old mice treated with vehicle or SAM, n = 3 for old mice treated with MCHA). c, (Left) The percentage of PI positive female MuSCs isolated at 2dpi (n = 4 for young mice, and old mice treated with vehicle or SAM, n = 3 for old mice treated with MCHA). (Right) The representative FACS plot. d-e, Frequency histogram of cross-sectional areas (CSAs) of centrally nucleated myofibers in TA muscle sections. TA muscles were harvested from old mice treated with vehicle, MCHA (d) or SAM (e) at 7 dpi (n = 3). f, (Left) Representative immunostaining of regenerating muscle fibers from female mice (Scale bar, 100 μm). (Right) Quantification of the mean CSAs of myofibers with centrally located nuclei in TA muscle sections (n = 4 for young and old female mice treated with vehicle, n = 3 for old female mice treated with MCHA or SAM). g, (Left) Representative immunostaining of non-regenerating muscle fibers (Scale bar, 100 μm). (Right) Quantification of the mean CSAs of myofibers in TA muscle sections (n = 3). h, (Top) Representative immunostaining of regenerating muscle fibers (Scale bar, 100 μm). (Bottom) Quantification of the mean CSAs of myofibers with centrally located nuclei in TA muscle sections (n = 3). i, Representative tissue immunostaining images of TA muscle sections from young mice collected at 7 dpi (n = 4, Scale bar, 100 μm). j, Quantification of the number of Pax7-positive MuSCs per each tissue section (n = 4). k, Old mice were given vehicle or MTA in drinking water, and MuSCs from each mouse were subjected to SAM ELISA (n = 4). l, (Top) Representative immunostaining of regenerating muscle fibers from old mice treated with vehicle or MTA (Scale bar, 100 μm). (Bottom) Quantification of the mean CSAs of myofibers with centrally located nuclei in TA muscle sections (n = 3). m, Grip force measured without injury (n = 4). n-o, Stance time (n) and stride time (o) were measured at 14 dpi (n = 8 for young mice, n = 7 for old mice treated with vehicle or SAM, n = 6 for old mice treated with MCHA). Data are shown as mean ± SD (a-c, f-h, j-o). P values were calculated by two-sided unpaired Student’s t-tests (e-g) and by one-sided student’s t test, pairwise between groups (a-c, f-h, j-o). *P < 0.05; **P < 0.01; ***P < 0.001.
