1997 VOLVO-AWARD WINNER IN BASIC SCIENCE STUDIES - IMMUNOHISTOLOGIC MARKERS FOR AGE-RELATED-CHANGES OF HUMAN LUMBAR INTERVERTEBRAL DISCS

Study Design. The authors performed a correlative macroscopic, histolo gic, and immunohistochemical investigation on human lumbar interverteb ral discs using complete motion segment slices, including all age grou ps and stages of degeneration. Objectives. To identify markers for age -related changes of human lumbar intervertebral discs. In particular, to investigate changes in the distribution pattern of collagen Types I , II, III, IV, V, VI, IX, and X. In addition, to study posttranslation al protein modification by the immunolocalization of N-(carboxylmethyl )lysine (CML), which is regarded as a biomarker for oxidative stress. Summary of Background Data. Data on a correlation of age-related chang es in disc morphology and disc matrix composition is sparse. So far, n o comprehensive analysis considered a correlation of macroscopic, hist ologic and biochemical age-related alterations using complete sections of intervertebral discs (i.e., including nucleus pulposus, anulus fib rosus, endplates, and vertebral bodies). In addition, there is need fo r specific markers for these disc changes to allow for a better correl ation with disc function. Methods. After photodocumentation of the mac roscopic appearance, 229 sagittal lumbar motion segments obtained from 47 individuals (fetal to 86 years) during routine autopsy were proces sed for histologic and immunohistochemical analysis. All slices were i nvestigated for histologic alterations of disc degeneration. A randoml y selected subset of these specimens (n = 45) was used for a correlati ve analysis of interstitial collagens and molecular modifications of m atrix proteins. Results. The presence of CML-modification of extracell ular matrix proteins, mainly collagen, was observed first in the nucle us pulposus of a 13-year-old individual and increased significantly wi th age. In elderly people, both the nucleus pulposus and the anulus fi brosus showed extensive CML deposition. This CML deposition was accent uated in areas of macroscopic and histologic disc degeneration. After the occurrence of CML in the nucleus pulposus, we found a change in th e collagen type pattern. An initial increase in nuclear collagen type pattern. An initial increase in nuclear collagen Types II, II, and VI staining was followed by a loss of collagen Type II, the occurrence of collagen Type I, and the persistence of high collagen Type III and VI levels, which were finally decreased again. The nuclear chondrocytes revealed significant changes in their immediate pericellular matrix, i ndicating phenotypic changes. Thus, exclusively in the nucleus pulposu s of adolescents and young adults a significant proportion of cells po sitively stained for the basement membrane collagen Type IV. Collagen Type X was expressed by nuclear chondrocytes at a higher age was assoc iated with advanced degenerative disc alterations. Conclusions. The au thors present the first study in which age-related changes are correla ted on a macroscopic, histologic, and molecular level using complete s ections of lumbar motion segments. They reconfirm the notion that disc damage may inhibit disc degeneration starts as early as in the second decade of life. Therefore, only early prevention of disc damage may i nhibit disc degeneration and its sequelae. Phenotypic alterations of n uclear chondrocytes as monitored by collagen Type IV in young adults w ith minor lesions and collagen Type X in advanced lesions indicate dis tinct cellular reactions, possibly as a reaction to enhanced oxidative stress. The degree of this oxidative stress is reflected by the CML-s taining pattern which, in turn, indicates that the disc undergoes an a ccumulative stress, possibly leading to altered properties of the coll agen fibrils and, thereby, tissue destruction. The deposition of CML p roved to be the best marker for ongoing age-related changes in the int ervertebral disc.