Surgical procedure. A columnar construct (4 mm in diameter and 6 mm in height) for the implantation (A). A cylindrical osteochondral defect in each groove before implantation (B). The construct composed of about 760 spheroids of AT-MSCs was autografted into the osteochondral defect in the right hind limb (C). Nothing was implanted into the left limbs (control defects; B).