Satellite cell and myofibre number per EDL myofibre in male and female mice across the lifespan.

<p>A) Isolated single fibres immunostained with Pax7 (i) and DAPI (ii) show myonuclei and satellite cells. Scale bar 50 µm. (B) 2 way analysis of variance test revealed a significant main effect of both age (p<0.0001) and gender (p = 0.003). Satellite cell numbers decline steadily with age: 2 week old mice have significantly more satellite cells per fibre than any other age group (8.5+/−0.93, 6.5+/−1.10 satellite cells/fibre in males and females respectively). Post hoc t tests show satellite cell numbers declined significantly between 2 weeks and 3 months (p = 0.03) 3 months and 1 year (p<0.001) and declined still further between 1 and 2.5 years (p<0.0001). Males were shown to have significantly greater numbers of satellite cells per fibre than females at 3 months (p = 0.02) and 1 year (p = 0.03) of age. At 2 weeks and 2.5 years, there was no difference between male and female satellite cell numbers per fibre. (C) 2 way analysis of variance test showed a significant effect of age (p<0.0001) and gender (p = 0.04) and an interaction between these variables (p<0.0001) on the number of myonuclei per fibre. The number of myonuclei per fibre increased significantly between 2 weeks and 3 months of age (p = 0.001) but showed a significant decline between 1 year and 2.5 years (p<0.001). Males had significantly more myonuclei per fibre than females at 3 months but at no other age investigated. Data show mean and s.e.m.