Unravelling the role of Mesenchymal Stem/Stromal Cells Secretome in intervertebral disc degeneration in a pro-inflammatory/degenerative ex vivo model
Abstract Background: Mesenchymal stem/stromal cells (MSCs) have been increasingly used in clinical trials for intervertebral disc (IVD) degeneration. Here, we aimed to evaluate the potential of a cell-free approach to degenerated IVD, testing if MSCs secretome can stimulate a regenerative response by modulating the IVD inflammatory cascade. Methods: Human bone marrow-derived MSCs were pre-conditioned with IL-1β (10 ng/mL) and low oxygen (6% O2). The secretome of MSCs (MSCsec) was collected after 48h. Bovine IVD tissue explants cultured in pro-inflammatory/degenerative conditions (needle puncture + IL-1β) were treated with MSCsec or co-cultured with MSCs. Results: MSCsec obtained upon IL-1β-pre-conditioning, as well as MSCs co-culture, down-regulated gene expression of pro-inflammatory cytokines, bIL-6 and bIL-8 after 48h, in IVD. IVD matrix degrading enzymes, bMMP1 and bMMP3, were downregulated and upregulated, respectively, in the presence of MSCsec, but not MSCs. After 14 days, MSCsec-treated IVDs revealed increased aggrecan content at the protein level, contrarily to MSCs/IVD co-cultures. Interestingly, IL-1β-preconditioning only, but not IL-1β-IVD, increased gene expression of hADAMTS5 and hTIMP-1in MSCs. Additionally, conditioned medium from MSCsec-treated IVDs did not promote angiogenesis or neurogenesis. In MSCsec-treated IVD, an increase in MCP-3 and GCP-2 was observed, while SDF-1α, TNF-α, IGF-1, Eotaxin 3, FGF-9, MIP-1δ, IFN-γ, IL-5, TNF-β, IL-4, TGF-β1, IL-16, IGFBP-3 and IGFBP-4 were decreased, compared with MSCs/IVD co-cultures. Conclusions: MSCsec obtained upon IL1β-preconditioning, present an immunomodulatory role in degenerated IVD, as well as MSCs. Nevertheless, MSCsec but not MSCs, potentiate aggrecan deposition in IVD in pro-inflammatory/degenerative conditions. This finding can open new perspective on the use of MSCsec as a cell-based/cell-free approach to LBP.