Calcification in intervertebral disc degeneration and scoliosis

In degenerative and scoliotic intervertebral discs (IVD), calcification is a pathological process that may lead to impairment of the nutrient supply and a disturbance in disc metabolism. However, the process of calcification in disc degeneration and scoliosis is not well understood. The purpose of this study was to assess the calcification markers in IVD of patients with degenerative disc disease and adolescent idiopathic scoliosis. For this purpose, 34 IVDs from 16 adult patients with degenerative disc disease and 25 IVDs from 9 adolescent patients with adolescent idiopathic scoliosis were obtained after surgery or autopsy. The concave and the convex parts of the scoliotic discs were analyzed separately. Von Kossa staining was performed to visualize calcium deposits, while type X collagen expression, which is associated with endochondral ossification, was measured by immunohistochemistry and Western blot. Alkaline phosphatase (ALP) activity and calcium and inorganic phosphate (Pi) concentrations were used as markers of the calcification process. Results showed the presence of calcium deposits and type X collagen only in degenerative and scoliotic intervertebral discs, but not in control discs. Results also demonstrated a large individual variability in ALP activity and calcium and Pi concentrations in degenerative and scoliotic discs. Moreover, the level of the calcification markers was consistently higher in degenerative and scoliotic discs than in control discs. The results suggest that disc degeneration in adults involves mineral deposition and that mineralization in adolescent idiopathic scoliosis discs might reflect an ongoing premature degenerative process.