Elevated synthetic activity in the convex side of scoliotic intervertebral discs and endplates compared with normal tissues.

STUDY DESIGN: We measured concentrations of specific molecules reflecting matrix synthesis and degradation in normal and scoliotic intervertebral discs and endplates.

OBJECTIVES: The aim of this work was to quantitate markers of matrix turnover in normal versus adolescent idiopathic scoliotic intervertebral discs and cartilaginous endplates.

SUMMARY OF BACKGROUND DATA: Changes in the intervertebral disc and endplate composition have been implicated as possible etiologic factors in the pathogenesis of adolescent idiopathic scoliosis. To better understand this process, it is important to compare the turnover of matrix components in scoliotic and normal intervertebral disc and endplate tissues. This comparison may help to improve our understanding of the role that disc and endplate tissues may play in the induction and/or progression of idiopathic scoliosis.

METHODS: Fifteen scoliotic and 17 normal intervertebral discs and endplates were analyzed for their water, collagen, proteoglycan, and protein content. In addition, newly synthesized aggrecan and collagen Types I and II were measured. Percent total denatured collagen was also determined.

RESULTS: The total collagen content was significantly lower in the scoliotic anulus and endplate regions, whereas glycosaminoglycan (GAG) content was significantly lower in the scoliotic endplates and nucleus regions. Conversely, total protein content was significantly higher in scoliotic endplates and elevated in scoliotic nucleus regions. Water content was significantly lower in the scoliotic anulus and endplate regions. When comparing the concave and convex regions of scoliotic endplates, there was no significant difference in concentration of any matrix component. The major difference in the synthetic marker levels relates to the synthesis of Type II collagen, which was higher in the nucleus, anulus, and endplate regions of scoliotic discs than in the corresponding regions of normal tissues. By contrast, the percent total denatured collagen was significantly elevated in the nucleus of normal tissues compared with the scoliotic ones.

CONCLUSIONS: The higher collagen Type II synthetic levels and increased total protein content with no matrix turnover suggest that scoliotic changes are due to an altered and ineffective synthetic response to a pathologic mechanical environment.