Fig. 3. SCs decline with age. (A-C) Syndecan-4 (Syn4, green), MyoD (red) and DAPI (blue) staining of freshly-isolated superficial TA fibres from 2-month-old (A), 12-month-old (B) and 24-month-old (C) mice. Arrows, myonuclei; arrowhead, SCs. Bar, 100 µm. (D,E) Pax7 staining (red) of fibres from 2-month-old (D) and 24-month-old mice (E). (F) Syn4⁺ SCs/fibre in large (>2500 µm²), medium (1500-2500 µm²) and small (<1500 µm²) fibres reveal that large adult fibres have more SCs and that the age-related decline in SCs is greatest on large fibres. (G) Comparison of the ratio of Syn4⁺ SCs to myonuclei (calculated as [Syn4⁺ cells.fibre^–1]/[DAPI⁺ nuclei/500 µm]), showing that large fibres lose their advantage by 24 months. Number of fibres counted are 20, 30 and 27 for small, medium and large fibres at 2 months, and 23, 37 and 38 at 1 year, and 45, 70 and 74 at 24 months.