Fig. 1.

Evaluation of PRG4, elastin, SDF1, CTGF, and TGF-beta1 expression in tendons and MTJs of young and old rats. a mRNA expression of PRG4, Eln, SDF1, CTGF, and TGFb1 in Achilles tendons of young (N = 9) and old (N = 7) rats. Values are normalized to RPL0 expression in each sample. *p < 0.05 indicates a significant difference between tendons of young and old rats. b Immunostaining of proximal TBA tendons from young and old rats with antibodies against PRG4, elastin, SDF1, CTGF, and TGF-beta1 (red in A–J). DAPI (blue) was used to co-stain the nuclei. Arrows indicate location of the fascicular sheets. Arrowheads indicate location of the tenocyte nuclei. c Relative levels of protein expression based on intensity of immunostaining of proximal TBA tendons from young and old rats with antibodies against PRG4, elastin, SDF1, CTGF, and TGF beta 1. *p < 0.05 indicates a significant difference between tendons of young and old rats. d Immunostaining of MTJ regions of TBA tendons from young and old rats with antibodies against PRG4, elastin, SDF1, CTGF, and TGF-beta1 (red in A–T). DAPI (blue) was used to co-stain the nuclei. WGA-fluorescein (green in A–T) was used to visualize connective tissue. Arrows indicate increased protein accumulation at the muscle/tendon border. Arrowheads indicate skeletal muscle fibers