Abstract
Introduction: Disc degeneration is consistent with advancing age and in many cases is associated with back pain and restricted mobility. The traditional surgical treatment for chronic back pain has been spinal fusion to immobilize the painful level. Long-term studies, however, suggest that fusion actually promotes degeneration at adjacent levels. One of the hallmarks of disc degeneration is aggregation of chondrocytes in the nucleus of chondrones, and more recently apoptosis has been implicated as a factor controlling the longevity of the cells. Recent research suggests that it may be possible to restore normal function to degenerate discs by introducing a fresh population of cells. This study investigated the potential for autologous costal chondrocyte implantation to prevent lumbar disc degeneration after annular injury in the sheep.
Methods: the lumbar spines of eight adult sheep were exposed. In four animals, full thickness annular incisions were made in three alternate discs. No annular incisions were made in the other four sheep. A minimum of 500 mg of cartilaginous tissue was harvested from the twelfth rib of all animals. Tissue was cultured in vitro and the chondrocytes were labelled with a fluorescent marker for retrospective identification. After six weeks the chondrocytes were injected into the lower two alternate discs of all animals, leaving the uppermost discs and those untouched as internal controls. The animals were killed at intervals from three to twenty-four weeks and MRI, plain x-ray, histology and immunocytochemistry were evaluated.
Results: MRI at twelve and twenty-four weeks showed apparent preservation of all incised discs that had been transplanted with autologous chondrocytes. Histology revealed clusters of viable chondrocytes of normal appearance within the nucleus. These cells stained positive for the fluorescent label. The same cells and the surrounding matrix were also positive for collagen type II. Serial X-ray measurements suggested that progressive disc degeneration was arrested in the discs that received autologous costal chondrocytes.
Discussion: This pilot study showed evidence that cultured autologous costal chondrocytes remained viable and produced extracellular matrix following transplantation into normal and degenerate discs. In contrast to other studies that have used mesenchymal stem cells or chondrocytes harvested directly from discs, this study demonstrated success with cells from a source other than the disc. Costal cartilage is a convenient source of cells for transplantation and this technique warrants further investigation as a potential treatment for degenerative disc disease.
The abstracts were prepared by I. B. McPhee. Correspondence should be addressed to the Spine Society of Australia Secretariat, The Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 5000, Australia.
