The belief that an intervertebral disc must degenerate before it can herniate has clinical and medicolegal significance, but lacks scientific validity. We hypothesised that tissue changes in herniated discs differ from those in discs that degenerate without herniation. Tissues were obtained at surgery from 21 herniated discs and 11 non-herniated discs of similar degeneration as assessed by the Pfirrmann grade. Thin sections were graded histologically, and certain features were quantified using immunofluorescence combined with confocal microscopy and image analysis. Herniated and degenerated tissues were compared separately for each tissue type: nucleus, inner annulus and outer annulus.

Herniated tissues showed significantly greater proteoglycan loss (outer annulus), neovascularisation (annulus), innervation (annulus), cellularity/inflammation (annulus) and expression of matrix-degrading enzymes (inner annulus) than degenerated discs. No significant differences were seen in the nucleus tissue from herniated and degenerated discs. Degenerative changes start in the nucleus, so it seems unlikely that advanced degeneration caused herniation in 21 of these 32 discs. On the contrary, specific changes in the annulus can be interpreted as the consequences of herniation, when disruption allows local swelling, proteoglycan loss, and the ingrowth of blood vessels, nerves and inflammatory cells.

In conclusion, it should not be assumed that degenerative changes always precede disc herniation.

Cite this article: Bone Joint J 2013;95-B:1127–33.

Objective and Background: Interleukin 1 has been implicated in the progression of degenerative disc disease, however little data is available on the expression and production of IL-1 within degenerate discal cells. A few studies, have investigated herniated disc tissue but the results from these studies have been inconsistent. This study investigated the gene expression of IL-1 α, β, Ra and the receptor type I in discs removed at surgery from 7 prolapsed, 3 Scoliosis and 15 Degenerative discs (DD). In addition immunohistochemistry (IHC) was used to localise IL-1 α and IL-1 β within normal, and degenerate discs.

Methods: Human IVD tissue was obtained from disc replacement surgery and separated into nucleus pulposus (NP) and annulus fibrosus (AF) tissue, cell isolation using collagenase treatment was carried out, and RNA extraction on the cells performed immediately. Real time RT-PCR was then used to investigate gene expression of IL-1 gene family. IHC for IL-1 α and IL-1 β was also performed on paraffin embedded normal and degenerate disc samples.

Results: Expression of the IL-1 family genes was present at low levels within prolapsed disc samples. In contrast levels within scoliosis patents were the highest of the 3 disease states, however in both prolapsed discs and those from scoliosis patients a balance of IL-1 α/β to IL-1 Ra existed. Within samples from DD this balance was lost, with levels of IL-1 α and IL-1 β greatly exceeding levels of IL-1 Ra. In addition levels of IL-1 α and β showed an increase with age and were highest in those samples from the AF than the NP. IHC demonstrated both IL-1 α and IL-1 β protein within the NP and AF cells of the degenerate discs.

Conclusion: This study has demonstrated the mRNA expression of all members of the IL-1 family within IVD and in addition the chondrocytes within the disc produced IL-1 α and IL-1 β protein. The imbalance of IL-1 α/β to IL-1 Ra within those samples from degenerate discs but not prolapsed or scoliotic discs suggests a role for IL-1 within discal degeneration.

Background: Current treatments for Low back pain (LBP) are often empirical and few directed at the underlying disorder, altered discal cell metabolism, which precipitates the problem. The use of gene therapy to manipulate discal metabolism to treat LBP is an interesting possibility. The Intervertebral disc (IVD) is a therapeutic target in LBP, and one approach to gene therapy would be to isolate IVD chondrocytes (IVDC) and transfer genes Ex Vivo into these cells. Subsequent reinjection of these genetically altered cells into the lumbar IVD, would permit the expression of the trans-gene in vivo, generating the therapeutic protein within the IVD.

Methods: To test the viability of this approach, we isolated human IVDC from patients undergoing surgery, grew them Ex vivo and transfected them with the marker gene LacZ, using an adenovirus vector and the CMV promoter. Expression of the gene was then measured using X-gal staining for the gene product ~-galactosidase.

Results: IVDC infected with adenovirus/CMV-LacZ showed maximal LacZ expression 2 days post infection, with almost 50% of cells displaying X-gal positivity within monolayer cultures and 100% infection within alginate culture, gene expression was maintained up to 4 weeks and control cultures showed no LacZ expression.

Conclusion: This study shows that human IVDC can be transfected with a foreign gene using the adenovirus vector. The gene transduction of a therapeutic gene into IVDC, could provide long lasting effect. In addition the use of inducible promoters could allow for the autoregulation of gene expression.