Biochemical and morphological changes in herniated human intervertebral disc.

The molecular and morphologic features of herniated human intervertebral disc tissues are of particular importance to clarify the pathogenesis. The present study analyzed the biochemical and morphological features of herniated intervertebral disc tissues to determine the constituent factors responsible for intervertebral disc herniation. A total of 32 herniated disc specimens and 4 control disc samples were analyzed. Collagen subunit composition, collagenase activity, lipid peroxidation level, caspase-3 activity, metal levels, morphologic studies, and genetic analysis were performed on herniated disc tissues of chronic (group A) and acute (group B) group and compared with findings of control group. Nick translation analysis in situ revealed apoptotic-positive stained DNA fragments as black-brown spots in herniated disc tissues. The presence of type II collagen in control disc samples and its absence in herniated samples were confirmed immunohistochemically. The increased caspase-3 activity, the apoptotic-positive stained DNA fragments, and the electron microscopic findings suggest enhanced programmed cell death in herniated discs. The significant increase in lipid peroxidation levels and collagenase activity, and the low metal levels suggest the enhancement of cell death signals in herniated discs, caused by oxygen stress. Linkage analysis of herniated disc tissues in Japanese individuals may suggest ethnic variation. These findings may be helpful in understanding the pathogenesis of herniated disc disease.