Background Osteoarthritis (OA) is the most common joint disease and the major cause of pain and disability in the aging population [1]. Adipose stromal cells (ASC) are promising candidate for cell therapy in OA, because they have immunomodulatory, trophic and differentiation capacities [2,3]. Synovial inflammation is accepted as important OA feature for the symptoms and disease progression [4]. Synovial tissue is mainly composed of synovial fibroblasts (SF), macrophages (SM) and a low percentage of other cell types [5].

Objectives Aim of the study was to analyze the effects of adipose stromal cells in co-culture with SF and SM.

Methods GMP clinical grade ASC were isolated from subcutaneous adipose tissue. Synoviocytes were isolated from synovial tissue of OA patients undergoing total joint replacement. Synovial cells at passage 1 and 5 were analyzed for: 1. different phenotypical markers by flow cytometric analysis, 2. inflammatory factors by multiplex immunoassay, 3.anabolic and degradative factors by qRT-PCR. Both p.1 (mix of SF and SM) and p.5 (only SF) synovial cells, as different cell models, were co-cultured with adipose stem cells (ASC) to define their effects. Furthermore macrophages type 1 (M1) were isolated and co-cultured with ASC.

Results Synoviocytes at passage 1 were positive to typical markers of SM (CD14,CD16,CD68, CD80,CD163) and SF (CD55,CD73,CD90,CD105,CD106), whereas at passage 5 were positive only to SF markers and showed a higher percentage of CD55 and CD106. At p.1 synovial cells released a significantly higher amount of all inflammatory (IL6,CXCL8,CCL2,CCL3,CCL5) and anabolic (IL10) factors than those at p.5. Moreover, p.1 synovial cells expressed also higher amount of some degradative factors (MMP13, S100A8, S100A9) than p.5 synovial cells. Co-culture experiments showed that the amount of SM in p.1 synovial cells specifically orchestrate the up or down-modulation of some inflammatory (IL6,CXCL8,CCL2,CCL3,CCL5) and degradative factors (ADAMTS5,MMP13, S100A8,S100A9) analyzed. Interestingly, p.5 synovial cells induced all factors analyzed, except CCL5. Finally, we demonstrated that ASC effects were strictly dependent by M1, that decreased the release of typical macrophages cytokines (IL1β, IL6, TNFα and CCL3/MIP1α) and that ASC effects are responsible for the switching by M1 like inflammatory macrophages to M2 like phenotype mainly due to PGE2 involvement.

Conclusions These data demonstrate that the GMP-ASC effects on OA synovial inflammation are strictly dependent by macrophages, that orchestrate the switching activated-M1 inflammatory macrophages to a M2-like phenotype, mainly through PGE2

References

1. Loeser RF (2012) Arthritis Rheum 64:1697–707.

2. C. Manferdini (2013) Arthritis Rheum 65:1271–81.

3. M. Maumus (2013) Stem Cell Research 11, 834–844.

4. Y. Henrotin (2014) Semin Arthritis Rheum 43(5):579–87.

5. MD. Smith (2011) The Open Rheumatology Journal 5:100–6.

References

Acknowledgements This research was supported by Horizon 2020 Programme (project ADIPOA2, grant agreement no: 643809). The materials presented and views expressed here are the responsibility of the authors only. The EU Commission takes no responsibility for any use made of the information set out.

Disclosure of Interest None declared