Chronic lower back pain affects millions of people year upon year and has a striking effect on quality of life. About 40% of chronic lower back pain is associated with the degeneration of the intervertebral disc. The current standard of care is heavily focused on symptomatic relief, with the last resort of surgical intervention. There is a lack of clinically available therapies that target the prevention of Intervertebral disc degeneration. In the field of intervertebral disc research, increased focus has been shifted to defining promising new treatments to enable disc regeneration. The reintroduction of cells within a biomaterial has theoretical promise, regarding restoring the main characteristics of cell loss and extracellular matrix degradation that are observed in disc degeneration.
This body of work consists of 7 chapters, chapter 1 delves into the understanding of the disease pathology, and reviews potential cell sources that have been investigated for nucleus pulposus regeneration within current literature. Chapter 2 facilitates future research with the chosen cell source, notochordal cells (NC), by providing key recommendations and methodologies for NC isolation within key species, numeration, in vitro manipulation and culture, and characterisation. The following chapter initiates research on screening biomaterials for cytocompatibility with primary porcine NCs (pNCs). The NC and biomaterial constructs were reviewed on the ability of biomaterials to maintain NC viability, phenotype, and extracellular matrix synthesis and deposition. As pNCs wouldn’t be an effective clinical cells source, an alternative NC-like cell source was utilised in Chapter 4. Which investigates biomaterial cytocompatibility with NC precursor cells, Mesendoderm progenitor cells derived from induced pluripotent stem cells (iPSC-MEPCs). Once more, this chapter aimed to identify a biomaterial that could enable the survival and differentiation of seeded iPSC-MEPCs into an NC-like phenotype with extracellular matrix synthesis and deposition. However, within Chapter 4 issues were raised with the cryopreservation and thawing of iPSC-MEPCs, therefore Chapter 5 analysed the method of differentiating iPSC into MEPCs, and the effects of cryopreservation on cells was also investigated and directly compared to the uninterrupted culture of MEPCs. With primary pNCs from Chapter 3 and iPSC-MEPCs from Chapter 5, Chapter 6 investigates the effect of external degenerative factors on these cell-seeded biomaterial constructs. The final chapter, chapter 7, summaries the results of the chapters and includes some future work that would be beneficial to investigate in future research. As this research investigates cell-seeded biomaterials that have clinical potential as an application for disc degeneration therapy, the translational potential was reviewed, and a recommendation of which patient profile would most benefit from this treatment was discussed.
This thesis includes extensive research with NC and precursor NCs and reviews the cytocompatibility of a selection of biomaterials for this chosen cell source. The research was carried out in vitro, with culturing the cell-seeded biomaterials in environments mimicking the disc and the degenerate disc. In conclusion, both cell sources survived in vitro culture of 4-weeks when seeded in select biomaterials, with some cells displaying regenerative properties. The number of available cells was a key limitation of this study and prevented an extensive multiple time point investigation. For future work with NCs, more research needs to be carried out in order to obtain a larger population ethically through primary sources or via stem cell differentiation.
