A comparative study of localization of heat shock protein 27 and heat shock protein 72 in the developmental and degenerative intervertebral discs

Study Design. The lumbar intervertebral discs of 135 subjects after autopsy were immunostained with antihuman heat shock protein 27 (HSP27) monoclonal antibody and antihuman heat shock protein 72 (HSP72) polyclonal antibody. Objectives. To present the data on metabolic changes that occurred in the chondrocytes of intervertebral discs during development and aging. Summary of Background Data. Heat shock proteins have been implicated in the progressive degeneration of articular cartilage in joint disease, such as rheumatoid arthritis and osteoarthritis. However, the role and expression of heat shock proteins in human intervertebral discs have received little study. Methods. One hundred thirty-five specimens of human intervertebral discs were stained with hematoxylin and eosin, alcian blue, and Masson's trichrome and were immunostained with HSP27 and HSP72 by an indirect immunoperoxidase method. The relative amounts of HSP27 and HSP72 deposition were graded according to a semiquantitative scoring system. Results. Heat shock protein 72 accumulated in the cytoplasm of the chondrocytes of both endplate cartilage and nucleus pulposus during gestation and thereafter decreased with aging (age, ≤60 years), and HSP72 immunoreactivity increased in the chondrocytes of degenerative discs. In addition, HSP72 was located in the nuclei of certain chondrocytes of the degenerated nucleus pulposus and anulus fibrosus, was highly expressed in the chondrocytes of endplate cartilage during gestation and childhood, and thereafter decreased with aging. Furthermore, with the progressive degeneration of the endplate cartilage, HSP27 immunoreactivity increased. The degree of HSP27 immunoreactivity did not change significantly according to age in either the nucleus pulposus or the anulus fibrosus. Conclusions. Heat shock protein 27 and HSP72 are thus considered to be useful molecular indicators for degenerative change in intervertebral discs. Both HSP27 and HSP72 are presumed to play a role in cell protection from stress that is induced by mechanical and biologic factors causing intervertebral disc degeneration.