Study purpose and background

Novel regenerative therapies have the potential to restore function and relieve pain in patients with low back pain (LBP) caused by intervertebral disc (IVD) degeneration. We have previously shown that stimulation of adipose-derived stem cells (ASCs) with growth differentiation factor-6 (GDF6) promotes differentiation into nucleus pulposus (NP) cells of the IVD, which have potential for IVD regeneration. We have also shown that GDF6 stimulation activates the Smad1/5/8 and ERK1/2 signalling cascades. The aim of this study was to progress our understanding of the immediate/early response mechanisms in ASCs (N=3) which may direct GDF6-induced differentiation.

Mesenchymal stem-cell based therapies have been proposed as novel treatments for intervertebral disc degeneration, a prevalent and disabling condition associated with back pain. The development of these treatment strategies, however, has been hindered by the incomplete understanding of the human nucleus pulposus phenotype and by an inaccurate interpretation and translation of animal to human research. This review summarises recent work characterising the nucleus pulposus phenotype in different animal models and in humans and integrates their findings with the anatomical and physiological differences between these species. Understanding this phenotype is paramount to guarantee that implanted cells restore the native functions of the intervertebral disc.

Cite this article: Bone Joint Res 2013;2:169–78.

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.