title: Disc cell clusters in pathological human intervertebral discs are associated with increased stress protein immunostaining.
abstract: Intervertebral disc (IVD) cells within the annulus fibrosus (AF) and nucleus pulposus (NP) maintain distinct functional extracellular matrices and operate within a potentially noxious and stressful environment. How disc cells respond to stress and whether stress is responsible for triggering degeneration is unknown. Disc cell proliferation and cluster formation are most marked in degenerate IVDs, possibly indicating attempts at matrix repair. In other tissues, stress proteins increase rapidly after stress protecting cell function and, although implicated in degeneration of articular cartilage, have received little attention in degenerative IVD pathologies. We have compared the distribution of stress protein immunolocalization in pathological and control IVDs. Disc tissues were obtained at surgery from 43 patients with degenerative disc disease (DDD) and herniation, and 12 controls at postmortem. Tissues were immunostained with a polyclonal antibody for heat shock factor 1 (HSF-1) and monoclonal antibodies for the heat shock proteins, Hsp27 and Hsp72, using an indirect immunoperoxidase method. Positively stained cells were expressed as a percentage of the total. Cell cluster formation was also assessed. The proportion of cells in clusters was similar in the AF (both 2%) and NP (8 and 9%) of control and DDD samples, whereas in herniated tissues this was increased (AF 12%, NP 14%). Stress antigen staining tended to be more frequent in clustered rather than in single/doublet cells, and this was significant (P < 0.005) in both the AF and NP of herniated discs. Clustered cells, which are most common in herniated discs, may be mounting a protective response to abnormal environmental factors associated with disc degeneration. A better understanding of the stress response in IVD cells may allow its utilization in disc cell therapies.
authors.affiliation: Charles Salt Centre for Human Metabolism, Robert Jones and Agnes Hunt Orthopaedic and District Hospital NHS Trust, Oswestry, Shropshire SY10 7AG, UK. chris.sharp@rjah.nhs.uk
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Sharp
authors.forename: Sally
authors.initials: S
authors.lastname: Roberts
authors.forename: Helena
authors.initials: H
authors.lastname: Evans
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Brown
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D004268:DNA-Binding Proteins / Q000378:metabolism*; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D006801:Humans; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D018832:Molecular Chaperones; D013122:Spinal Diseases / Q000378:metabolism* / Q000473:pathology; D014157:Transcription Factors / Q000378:metabolism*; D055815:Young Adult
chemical_list: D004268:DNA-Binding Proteins; D055551:HSP27 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; C057725:HSPB1 protein, human; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D014157:Transcription Factors