Fig. 2

EVs derived from hydroxycamptothecin-primed human umbilical cord stem cells (HCPT-EVs) more effectively ameliorated tendon adhesion in a rat model of tendon injury. EVs derived from unprimed human umbilical cord mesenchymal stem cells (Unprimed EVs), HCPT-EVs, or PBS were subcutaneously injected into the injury site, and tendon tissues were harvested at 3 weeks postsurgery. a Representative images showing surgical procedures and macroscopic observation of the repaired tendon and concomitant adhesion. b Adhesion grading score (n = 5 per group) for macroscopic rating of tendon adhesion. c Hematoxylin-eosin (HE) staining for tendon adhesion observation. Lower panels are magnified images of the boxed areas indicated in the upper panel. d Masson’s trichrome staining for tendon adhesion observation. Histological rating of tendon adhesion and healing using, e histological adhesion score (n = 5 per group), f histological healing score (n = 5 per group), and g biomechanical testing for maximal tensile strength of repaired tendon (n = 5 per group). The capital letter “T” denotes tendon. The dotted lines represent the boundaries between the tendon and peritendinous tissues and encapsulate the adhesion tissues. Black triangles indicate the adhesive tissues. *P < 0.05, ***P < 0.001; ns, not significant