The Chondrogenic Potential of the Bovine Tendon Sheath - a Novel Source of Stem Cells for Cartilage Repair.

The human hand is traumatized more frequently than any other bodily part. Trauma and pathological processes (e.g., rheumatoid arthritis, osteoarthritis) commonly implicate the finger joints and specifically damage also the layer of articular cartilage. Endeavors are now being made to surgically repair such cartilage lesions biologically using tissue-engineering approaches that draw on donor cells and/or donor tissues. The tendon sheaths, particularly their inner layers, i.e., the peritendineum, surround the numerous tendons in the hand. The peritendineum is composed of mesenchymal tissue. We hypothesize that this tissue harbors pluripotent mesenchymal stem cells and thus could be used for cartilage repair, irrespective of the donor's age. Using a bovine model (young calves vs. adult cows), the pluripotentiality of the peritendineal stem cells, namely, their osteogenicity, chondrogenicity, and adipogenicity, was investigated by implementing conventional techniques. Subsequently, the chondrogenic potential of the peritendineal tissue itself was analyzed. Its differentiation into cartilage was induced by the application of specific growth factors (members of the TGF-β-superfamily). The characteristics of the tissue formed were evaluated structurally (immuno) histochemically, histomorphometrically, and biochemically (gene expression and protein level). Our data confirm that the bovine peritendineum contains stem cells whose pluripotentiality is independent of donor age. This tissue could also be induced to differentiate into cartilage, likewise, irrespective of the donor's age. Preliminary investigations with adult human peritendineal biopsy material derived from the hand's peritendineal flexor tendon sheaths revealed that this tissue can also be induced to differentiate into cartilage.