Costal cartilage autografts to simulated degenerative intervertebral discs in the rat

An autograft of costal cartilage was transplanted into the rat intervertebral space in the proximal tail following 2 weeks of simulated degeneration by chondroitinase ABC (CABC). The purpose of this study was to evaluate costal cartilage transplantation into a degenerated disc as a possible therapy. Reversal of degenerative disc dehydration is an attractive goal. Costal cartilage is plentiful, hydrophilic, and avascular, leading us to speculate that it would survive transplantation into the degenerated disc, increase proteoglycan content, and restore disc height. Costal cartilage fragments were transplanted into a single proximal intervertebral disc in each of the rats' tails following a 2-week period of simulated degeneration. The intervertebral space was measured on radiographs under 2.5x magnification taken pretreatment and 21 days posttreatment. Each specimen was sagittally sectioned, mounted, and stained. The slides were graded for proteoglycan content. A 64% increase in intervertebral disc height was observed in the implant group compared with a 4% increase in sham operated group and a 39% increase in the CABC only group. Histology demonstrated a viable implant in 7 of 9 rats. The transplant group had significantly more proteoglycan staining than either the CABC group or sham group (P < 0.05). Costal cartilage transplantation may rehydrate degenerated intervertebral discs and might serve as a promising model for understanding and perhaps modifying this complex degenerative disease.