Abstract
Introduction: Elastin is a structural protein forming a highly organised network in the annulus and nucleus of the intervertebral disc (IVD). It appears important in maintaining annulus structure as it is densely located in the interlamellar space and forms cross-bridges between lamellae. Here we have investigated elastin fibre organisation in degenerate discs and compared it to that seen in normal human and bovine discs.
Methods: Human lumbar IVD were obtained from consented patients undergoing surgery either for disc degeneration, tumour or trauma. The disc segments were collected from operating theatre and graded. A radial profile of the specimen was dissected and snap-frozen. Sections of 20μm in thickness were cut with a cryostat microtome and mounted on slides. To visualize elastin fibres, sections were digested with hyaluronidase after fixation with 10% of formalin. Elastin fibres were immunostained and fibre organisation mapped.
Results: In degenerate disc, the elastin fibre network appeared sparse and disorganised in comparison to that seen in non-degenerate human or in bovine discs in which elastin fibres are well organised. In addition, in degenerate discs the elastin fibres appear fragmented. Fragmentation of the elastin network within lamellae of the annulus in particular increased with both degeneration grade and with age.
Discussion: The loss of elastic network integrity observed in degenerate discs could contribute to loss of annulus integrity and affect disc mechanical properties adversely. Furthermore, our initial results have suggested fragmented elastin degradation products could upregulate MMP expression by disc cells thus stimulating a degenerative cascade.
Correspondence should be addressed to Ms Alison McGregor, c/o BOA, SBPR at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
