Fig. 5

Muscle stem cell function is impaired in ΔKlotho mice. a Myofibers with their adjacent muscle stem cells were isolated from EDL muscles of p42 old mice and directly fixed and stained with antibodies directed against Pax7 (red) and DNA (DAPI, blue). Arrows point at Pax7-positive muscle stem cells. Scale bar = 50 μm. b Representative images of clusters of muscle stem cells on their adjacent EDL myofibers isolated at p42 and cultured for 72 h and then stained with antibodies directed against MyoD (green), Pax7 (red), and DNA (DAPI, blue). Scale bar = 50 μm. c The number of Pax7-positive muscle stem cells per myofiber was quantified from p42 ΔKlotho and control mice. (ΔKlotho n = 5 mice, control n = 7 mice). d The number of clusters per myofiber isolated from p42 animals and cultured for 72 h of culture was enumerated. (ΔKlotho n = 5 mice, control n = 7 mice). e The number of cells per cluster per myofiber isolated from p42 animals and cultured for 72 h was determined. (ΔKlotho n = 5 mice, control n = 7 mice). f The composition of clusters shows a reduction in the proportion of further differentiated cells (Pax7−/MyoD+) in ΔKlotho compared to control mice at p42. (ΔKlotho n = 5 mice, control n = 7 mice). g Addition of recombinant sKlotho to fiber cultures from ΔKlotho mice results in an increase in cluster number per myofiber (n = 3). All data are presented as means ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001