Identification of the collagen-producing cells in healing flexor tendons.

: A monoclonal antibody to procollagen type I (anti-pC) which specifically stains cells synthesizing collagen was used to study the healing of chicken flexor tendons in vivo. Healing was assessed using routine hematoxylin and eosin histology and immunoperoxidase staining with anti-pC. Studies showed that epitenon cells proliferate 3 days after injury and are producing collagen by 7 days after injury. Tenocytes do not begin producing collagen until 14 to 21 days after injury. From 3 to 5 weeks, the entire substance of the tendon becomes filled with collagen-synthesizing cells. These cells may have originated from the tendon sheath, the epitenon, or the endotenon; however, the evidence presented in this study suggests that the epitenon is a major source of these cells.