Repair of extensive articular cartilage defects in horses by autologous chondrocyte transplantation.

Damaged adult articular cartilage has very limited capacity to heal. Autologous chondrocyte transplantation (ACT) has been used clinically and studied in experimental animals in an attempt to provide biologically based cartilage regeneration. This study evaluated cartilage repair following ACT in a large animal model over a period of 2 years. Articular cartilage defects (10 mm in diameter, full-thickness) were created in the minor load-bearing area on the lateral talus of tibiotarsal joints of eight adult horses. In each animal, the right joint was repaired using autologous chondrocytes injected beneath the periosteum, as in the original ACT procedure (Brittberg, M., A. Lindahl, A. Nilsson, C. Ohlsson, O. Isaksson, and L. Peterson N. Engl. J. Med. 331:889-895, 1994): the left joint remained untreated to serve as a control. Clinical and pathological evaluation was within the range of normal for all horses at both time points. Compared to untreated defects, ACT resulted in significantly improved defect filling with a well-integrated neocartilage and comparable expression of cartilage-specific markers. The histological score (Peterson, L., T. Minas, M. Brittberg, A. Nilsson, E. Sjogren-Jansson, and A. Lindahl Clin. Orthop. 374:212-234, 2000) (10.4 +/- 0.9 for ACT and 5.6 +/- 3.9 for controls, all animals, p = 0.016) indicated that ACT contributed to the reparative process. For the first time, the efficacy of ACT was demonstrated in a large animal model supporting the potential of ACT for cartilage regeneration in patients.