Background. Degeneration of the intervertebral disc (IVD) is a leading cause of lower back pain, and a significant clinical problem. Inflammation mediated by IL-1β and TNF-α drives IVD degeneration through promoting a phenotypic switch in the resident nucleus pulposus (NP) cells towards a more catabolic state, resulting in extracellular matrix degradation. Bone marrow mesenchymal stem cells (MSCs) produce bioactive factors that modulate local tissue microenvironments and their anti-inflammatory potential has been shown in numerous disease models. Thus MSCs offer a potential therapy for IVD degeneration. In a clinical setting, adipose-derived stem cells (ASCs) might represent an alternative and perhaps more appealing cell source. However, their anti-inflammatory properties remain poorly understood. Methods. Here we assess the anti-inflammatory properties of donor-matched human ASCs and MSCs using qPCR and western blotting. Results. We demonstrate that stimulating ASCs or MSCs with IL-1β and/or TNF-α elicits a strong anti-inflammatory response with increased expression of IL-1 receptor antagonist (IL-1Ra), cyclooxygenase-2 (COX-2) and the tissue protective protein tumour-necrosis factor stimulated gene-6 (TSG-6). ASCs produced significantly higher levels of IL-1Ra and TSG-6 than their matched MSCs at both gene and protein levels, indicating that ASCs are potentially a more potent anti-inflammatory cell type. This anti-inflammatory response was also observed upon co-culture with degenerate NP cells without exogenous cytokine. Signalling analyses suggested this difference between cell types might be mediated through differences in the activation of inflammation-associated transcription factors. Conclusion. These data indicate that the anti-inflammatory properties of ASCs may be useful in developing future therapies for IVD degeneration. No conflicts of interest. Sources of funding: EPSRC-MRC Centre for Doctoral Training in
Introduction. Intervertebral disc degeneration (IVDD) associated with low back pain is a major contributor to global disability. Current treatments are poorly efficient in the long-term resulting in medical complications. Therefore, minimally invasive injectable therapies are required to repopulate damaged tissues and aid regeneration. Among injectable biomaterials, self-assembling peptide hydrogels (SAPHs) represent potential candidates as 3D cell carriers. Moreover, the advent of graphene-related materials has opened the route for the fabrication of graphene-containing hydrogel nanocomposites to direct cellular fate. Here, we incorporated graphene oxide (GO) within a SAPH to develop a biocompatible and injectable hydrogel to be used as cell carrier to treat IVDD. Methods and results. Hydrogel morphology and mechanical properties have been investigated showing high mechanical properties (G'=12kPa) comparable with human native nucleus pulposus (NP) tissue (G'=10kPa), along with ease of handling and injectability in dry and body fluid conditions. Hydrogel nanocomposites resulted biocompatible for the encapsulation of bovine NP cells, showing higher viability (>80%) and metabolic activity in 3D cell culture over 7 days, compared to GO-free hydrogels. Moreover, GO has demonstrated to bind TGF-β3 biomolecules with high efficiency, suggesting the use of GO as local reservoir of growth factors within the injected hydrogel to promote extracellular matrix deposition and tissue repair. Conclusions. Our results show that incorporation of GO within the SAPH improves cell viability and metabolic activity. Furthermore, its tissue-mimicking mechanical properties and chemical tunability make it a promising candidate as injectable carrier of NP cells for the treatment of IVDD. Part of this work has been published (DOI: 10.1016/j.actbio.2019.05.004). Conflicts of interests: No conflicts of interest. Sources of funding: The authors thank the EPSRC & MRC CDT in
