Histological sections of the supraspinatus and infraspinatus tendons in sheep. Histological sections of the supraspinatus (MacNeal's tetrachrome stain (A, B, and C)) and infraspinatus (toluidine blue stain (D, E, and F)) tendons in sheep demonstrate that the normal enthesis exhibits a typical bone-calcified fibrocartilage-fibrocartilage interface (A, E). The surgical control (B, E) transitions from bone directly into scar tissue in both tendons after 16 weeks. In contrast, the scaffold-treated supraspinatus tendon (C) demonstrates the regeneration of the bone-calcified fibrocartilage-fibrocartilage interface and a regrowth of tendon midsubstance, although the calcified fibrocartilage and fibrocartilage layers are thicker in the repair than in the normal animals. A similar response was observed in the scaffold-repaired infraspinatus tendon (F).