Figure 8. Elastase treatment impairs primary myoblast growth and differentiation rates.

(a,c,d) Representative images of primary myoblasts seeded on collagen type I (a), collagen type IV (c) or laminin (e) and either non-treated or treated with elastase (0.45 U/mL and 0.9 U/mL) for 1 and 2 days. (b,d,f) Quantification of (a,c,e), respectively. For quantification, 10 images per experiment across 3 independent experiments (N = 30 images) were scored for cell numbers, averaged and plotted as a function of time. (g) Representative images of primary myoblasts maintained in differentiation medium for three days then immunostained to detect myosin heavy chain (MyHC, green) and DAPI (blue). (h) The differentiation index was calculated as the percentage of MyHC + cells over the total number of DAPI + cells, then for each culture condition (Col I, Col IV and Lam) the differentiation index of non-treated cells was set to 100% and the differentiation index of treated cells expressed as a fraction of 100 in order to average different experiments. Ten images per experiment across 3 independent experiments were analysed (N = 30). (i) The fusion index was calculated as the percentage of MyHC + cells in myotubes over the total number of MyHC + cells, then for each culture condition (Col I, Col IV and Lam) the fusion index of non-treated cells was set to 100% and the fusion index of treated cells expressed as a fraction of 100 in order to average different experiments. Ten images per experiment across 3 independent experiments were analysed (N = 30). Error bars are S.E.M.; **p < 0.01; ^#p > 0.05. Scale bars are 100 μm.