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. 2021 May 6;12(3):746–768. doi: 10.1002/jcsm.12700

Figure 1.

Figure 1

Identification of Tfr1 as a key biomarker regarding skeletal muscle ageing and satellite cell (SC) activity. (A) Venn diagraph showing overlapped genes between young (2 weeks old) and aged (80 weeks old) mice among four types of muscle [transverse abdominal (TA), extensor digitorum longus (EDL), soleus (Sol), and gastrocnemius (Gas)] (n = 3 per group). (B) Gene ontology (GO: biological process) analysis against down‐regulated genes between 2‐ and 80‐week‐old C57BL/6J mice. (C) Gene Set Enrichment Analysis (GSEA) analysis of down‐regulated pathway in response to the iron homeostasis. (D) Heatmap of cellular iron homeostasis‐related gene expression in TA muscle across five different ages (2, 8, 30, 60, and 80 weeks old). (E) qPCR analysis of Tfr1 expression in four types of skeletal muscles (TA, EDL, Sol, and Gas) between 2‐ and 8‐week‐old C57BL/6J mice (n = 5 per group). (F) Representative western blot image of four types of skeletal muscles (TA, EDL, Sol, and Gas) between 2‐ and 8‐week‐old C57BL/6J mice (n = 5 per group). (G) Representative images of myofibres isolated from 2‐ and 8‐week‐old C57BL/6J mice (n > 50 myofibres from five mice per group). Immunofluorescence of Pax7 (red), Tfr1 (green), Ki67 (pink), and DAPI (blue) staining revealed that Tfr1 is highly expressed in SCs at proliferative state (Ki67+) for 2‐week‐old mice but not 8‐week‐old adult mice. (H) Number of Ki67+ and Ki67− SCs with different Tfr1 expression level (High, Inter, and Low) per myofibre. (I) Number of Pax7+ SCs per myofibre. (J) Number of Ki67+ and Ki67− SCs per myofibre. N.S., not significant, **P < 0.01, and ***P < 0.005, by two‐sided Student's t‐test. Data represent the mean ± standard error of the mean.