Figure 4 : Generation of satellite cells from AP+-derived cells during mouse growth.

From: Pericytes resident in postnatal skeletal muscle differentiate into muscle fibres and generate satellite cells

Figure 4

(a) Immunohistochemistry on Tg:TN-AP-CreERT2:R26R Pectoralis muscle sections, 1 week after tamoxifen injection, stained for β-gal (blue) and anti-Pax7 (brown). The majority of Pax7+ cells are β-gal negative (brown arrows), whereas vessels are blue (blue arrows). Only few double-positive cells are detectable (green arrow). Insets show high magnification. (b) Immunohistochemistry on Tg:TN-AP-CreERT2:R26R Pectoralis muscle sections 1 month after last tamoxifen injection stained for β-gal (blue) and Pax7 (brown). Several Pax7+/β-gal+ satellite cells were detected (green arrows) together with β-gal+ fibres. Insets show high magnification. (cf) TA muscle section of Tg:TN-AP-CreERT2:R26R mouse, 2 months after tamoxifen injection. A Pax7+ (green) satellite cell also expresses β-gal (red) (arrows); the satellite cell is associated to a β-gal-negative fibre. Laminin is stained in magenta. Scale bar, 100 μm. (g) Pax7+/β-gal+ satellite cells counted on the total number of Pax7+ satellite cells, in different muscles and at different time points after tamoxifen induction: 1 week (pale blue), 2 weeks (dark blue), 3 weeks (pale grey), 4 weeks (dark grey). Number of experimental animals: n=5. Error bars indicate standard deviation. Results were assessed for statistical significance by Student's t-test (unpaired, two-tailed) and differences were considered statistically significant at P<0.05. Asterisks in the histogram indicate the different P values: **P<0.01 and ***P<0.001. (h) Total number of satellite cells for microscopic field (~0.5 mm2) at different time points after tamoxifen induction in Pectoralis muscle. Blue bars indicate the number of Pax7+/β-gal− satellite cells; red bars indicate the number of Pax7+/β-gal+ satellite cells. The total number of Pax7+ cells decreases with time, whereas the number of double-positive Pax7+/β-gal+ cells increases until 3 weeks after tamoxifen induction, remaining constant afterwards. Number of experimental animals: n=5. Error bars indicate standard deviation. Results were assessed for statistical significance by Student's t-test (unpaired, two-tailed) and differences were considered statistically significant at P<0.05. Asterisk in the histogram indicates P value: *P<0.05.