Intra-articular administration of adipose-derived mesenchymal stem cells (ASCs), either in vitro expanded or within adipose tissue-based products obtained at point-of-care, has gained popularity as innovative regenerative medicine approach for osteoarthritis (OA) treatment. ASCs can stimulate tissue repair and immunomodulation through paracrine factors, both soluble and extracellular vesicles (EV) embedded, collectively defining the secretome. Interaction with the degenerative/inflamed environment is a crucial factor in understanding the finely tuned molecular message but, to date, the majority of reports have described ASC-secretome features in resting conditions or under chemical stimuli far from the in vivo environment of degenerated OA joints. In this report, the secretory profile of ASCs treated with native synovial fluid from OA patients was evaluated, sifting 200 soluble factors and 754 EV-embedded miRNAs. Fifty-eight factors and 223 EV-miRNAs were identified, and discussed in the frame of cartilage and immune cell homeostasis. Bioinformatics gave a molecular basis for M2 macrophage polarization, T cell proliferation inhibition and T reg expansion enhancement, as well as cartilage protection, further confirmed in an in vitro model of OA chondrocytes. Moreover, a strong influence on immune cell chemotaxis emerged. In conclusion, obtained molecular data support the regenerative and immunomodulatory properties of ASCs when interacting with osteoarthritic joint environment.

The study of the miRNA cargo embedded in extracellular vesicles (EVs) released from adipose-derived mesenchymal stromal cells (ASC) preconditioned with IL-1β, an inflammatory stimulus driving osteoarthritis (OA), along with EVs-cartilage dynamic interaction represent poorly explored fields and are the purpose of the present research. ASCs were isolated from subcutaneous adipose tissue and EVs collected by ultracentrifugation. Shuttled miRNAs were scored by high-throughput screening and analyzed through bioinformatics approach that predicted the potentially modulated OA-related pathways. Fluorescently labeled EVs incorporation into OA cartilage explants was followed in vitro by time-lapse coherent anti-Stokes Raman scattering; second harmonic generation and two-photon excited fluorescence. After IL-1β preconditioning, 7 miRNA were up-regulated, 4 down-regulated, 37 activated and 17 silenced. Bioinformatics allowed to identify miRNAs and target genes mainly involved in Wnt, Notch, TGFβ and Indian hedgehog (IHH) pathways, cartilage homeostasis, immune/inflammatory responses, cell senescence and autophagy. As well, ASC-EVs steadily diffuse in cartilage cells and matrix, reaching a plateau 16 h after administration. Overall, ASCs preconditioned with IL-1β allows secretion of EVs embedded with a chondro-protective miRNA cargo, able to fast penetrate in collagen-rich areas of cartilage with tissue saturation in a day. Further functional studies exploring the EVs dose-effects are needed to achieve clinical relevance.

Inflammatory processes contribute to osteoarthritis (OA) severity and progression. Mesenchymal stem cells, particularly those derived from adipose tissue (ASCs), are able to sense and control the inflammatory environment. This immunomodulatory potential can be boosted by different priming strategies based on inflammatory stimulation. The aim of the present study is to investigate the transcriptional modulation of a huge panel of genes and functionally verify the predicted immunomodulatory ability of ASCs after interleukin one beta (IL-1β) priming. ASCs were isolated from adipose tissue obtained from three donors and expanded. After stimulation with 1 ng/ml of IL-1β for 48 h, cells were collected for gene array and functional tests. Pooled cells from three donors were used for RNA extraction and gene array analysis. Gene Ontology (GO) enrichment analysis and Gene Set Enrichment Analysis (GSEA) were performed to assess the involvement of the modulated genes after priming in specific biological processes and pathways. Functional co-culture tests of ASCs with T cells and macrophages were performed to assess the ability of primed ASCs to modulate immune cell phenotype. Among the overall genes analyzed in the gene array, about the 18% were up- or down-regulated in ASCs after IL-1β priming. GO enrichment analysis of up- or down-regulated genes in ASCs after IL-1β priming allowed identifying specific pathways involved in the modulation of inflammation and extracellular matrix remodeling. The main processes enriched according to the GSEA are related to the inflammatory response and cell proliferative processes. Functional tests on immune cells showed that primed and non-primed ASCs induced a decrease in the CD3⁺ T lymphocytes survival rate and an anti-inflammatory macrophage polarization. In conclusion, IL-1β priming represents a tailored strategy to enhance the ability of ASCs to direct macrophages towards an anti-inflammatory phenotype and, consequently, improve the efficacy of ASCs in counteracting the OA inflammatory component.

Bone-marrow-mesenchymal-stromal-cells (BMSCs)- and platelet-rich-plasma (PRP)-based therapies have shown potential for treating osteoarthritis (OA). Recently, the combination of these two approaches was proposed, with results that overcame those observed with the separate treatments, indicating a possible role of PRP in ameliorating BMSCs’ regenerative properties. Since a molecular fingerprint of BMSCs cultivated in the presence of PRP is missing, the aim of this study was to characterize the secretome in terms of soluble factors and extracellular-vesicle (EV)-embedded miRNAs from the perspective of tissues, pathways, and molecules which frame OA pathology. One hundred and five soluble factors and one hundred eighty-four EV-miRNAs were identified in the PRP-treated BMSCs’ secretome, respectively. Several soluble factors were related to the migration of OA-related immune cells, suggesting the capacity of BMSCs to attract lympho-, mono-, and granulocytes and modulate their inflammatory status. Accordingly, several EV-miRNAs had an immunomodulating role at both the single-factor and cell level, together with the ability to target OA-characterizing extracellular-matrix-degrading enzymes and cartilage destruction pathways. Overall, anti-inflammatory and protective signals far exceeded inflammation and destruction cues for cartilage, macrophages, and T cells. This study demonstrates that BMSCs cultivated in the presence of PRP release therapeutic molecules and give molecular ground for the use of this combined and innovative therapy for OA treatment.