Fig. 1: PI3K-Akt signalling pathway is specifically activated in injured tendons of neonatal mice.

a Schematic of the sample collection protocol for RNA-sequence analysis. The 7-day-old (P7d) or 6-month-old (P6m) Scx-EGFP mice underwent Achilles tenotomy on the right hind limb (tenotomy group) and a sham operation (sham group) on the left hind limb. Injured and uninjured Achilles tendons were collected 5 days later. Five to eleven individual samples were pooled in each group and used in the RNA-sequencing analysis (7-day sham, n = 11; 7-day cut, n = 11; 6-month sham, n = 5; 6-month cut, n = 9). b KEGG pathway analyses for the neonatal and adult tenotomy groups; 29 and 77 upregulated pathways were identified in neonatal and adult tenotomy groups, respectively. A Venn diagram comparing the upregulated pathways between the neonatal and adult tenotomy groups shows five specifically upregulated pathways in neonatal mice. c The five specifically upregulated pathways in the neonatal tenotomy group. d Western blot analysis of injured neonatal (P7d) and adult (P6m) tendons on post-tenotomy day 5. Three independent samples were analysed in neonatal and adult mice. e Quantification of the pAkt/Akt ratio shown in (d). Akt phosphorylation (pAkt) was higher in neonates than in adults. Data are shown as the mean ± SEM of three independent samples in each group (two-tailed Student’s t test; P = 0.0344). f Haematoxylin-eosin staining (H&E) and fluorescent immunohistochemistry of pAkt in the injured neonatal (P7d) and adult (P6m) tendons on post-tenotomy day 5. The black square areas in the left panels are enlarged. Strong pAkt expression was observed at the distal stub of the neonatal injured tendon. Scale bars, 200 μm and 50 μm.