Degeneration and the chemical composition of the human lumbar intervertebral disc

Fifteen lumbar spines were collected postmortem. The intervertebral discs were assigned morphological grades and were analyzed for water, collagen, and proteoglycan. In order of increasing degeneration, five grade 0, four grade 1, 45 grade 2, 12 grade 3A, and nine grade 3B discs were identified. The proteoglycan concentration fell progressively with increasing grade, although the concentrations of each component overlapped extensively among the grades. Grade 2 discs showed no consistent differences from adjacent grade 3A or 3B discs in the same spine. All discs in seven of the eight spines with grade 3A or 3B discs and all discs in three spines with no grade 3A or 3B discs had proteoglycan concentrations below 52 mg/g fresh weight. Four of five spines with at least one disc of proteoglycan concentration above this value contained no grade 3A or 3B discs. These observations support the hypothesis that low proteoglycan concentrations in all the discs of a spine precede degeneration.