Background/aims: Synovial fibrosis is a pathological process that is observed in several musculoskeletal disorders and characterized by the excessive deposition of extracellular matrix, as well as cell migration and proliferation. Despite the fact that glucocorticoids are widely employed in the treatment of rheumatic pathologies such as osteoarthritis (OA) and rheumatoid arthritis, the mechanisms by which glucocorticoids act in the joint and their impacts on pro-fibrotic pathways are still unclear. Materials: Human OA synovial fibroblasts were obtained from knee and hip joints. Cells were treated with prednisolone (1 mM) or transforming growth factor-beta 1 (TGF-β1) (10 ng/ml) for 1 and 7 days for quantification of RNA and protein expression (by real-time quantitative reverse transcription-PCR and western blot, respectively), 72 h for immunocytochemistry analysis, and 48 h for proliferation (by BrdU assay) and migration (by wound assay) studies. In addition, cells were preincubated with prednisolone and/or the peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist 15-deoxy-Δ-12,14-prostaglandin J2 (15d-PGJ2) for 6 h before adding TGF-β1. pSmad1/5, pSmad2 and β-catenin levels were analyzed by Western blot. The activin receptor-like kinase-5 (ALK-5) inhibitor (SB-431542) was employed for the mechanistic assays. Results: Prednisolone showed a predominant anti-fibrotic impact on fibroblast-like synoviocytes as it attenuated the spontaneous and TGF-β-induced gene expression of pro-fibrotic markers. Prednisolone also reduced α-sma protein and type III collagen levels, as well as cell proliferation and migration after TGF-β stimulation. However, prednisolone did not downregulate the gene expression of all the pro-fibrotic markers tested and did not restore the reduced PPAR-γ levels after TGF-β stimulation. Interestingly, anti-fibrotic actions of the glucocorticoid were reinforced in the presence of the PPAR-γ agonist 15d-PGJ2. Combined pretreatment modulated Smad2/3 levels and, similar to the ALK-5 inhibitor, blocked β-catenin accumulation elicited by TGF-β. Conclusions: Prednisolone, along with 15d-PGJ2, modulates pro-fibrotic pathways activated by TGF-β in synovial fibroblasts at least partially through the inhibition of ALK5/Smad2 signaling and subsequent β-catenin accumulation. These findings shed light on the potential therapeutic effects of glucocorticoids treatment combined with a PPAR-γ agonist against synovial fibrosis, although future studies are warranted to further evaluate this concern.Keywords: Fibroblast-like-synoviocytes; Fibrosis; Glucocorticoids; Osteoarthritis; Peroxisome proliferator-activated receptor-γ agonist; Transforming growth factor-β1.

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乐备实（上海优宁维生物科技股份有限公司旗下全资子公司），是国内专注于提供高质量蛋白检测以及组学分析服务的实验服务专家，自2018年成立以来，乐备实不断寻求突破，公司的服务技术平台已扩展到单细胞测序、空间多组学、流式检测、超敏电化学发光、Luminex多因子检测、抗体芯片、PCR Array、ELISA、Elispot、PLA蛋白互作、多色免疫组化、DSP空间多组学等30多个，建立起了一套涵盖基因、蛋白、细胞以及组织水平实验的完整检测体系。

 
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