The Paracrine Effect of Adipose-Derived Stem Cells Inhibits IL-1β-induced Inflammation in Chondrogenic Cells through the Wnt/β-Catenin Signaling Pathway

Abstract

Stem cell therapy has the potential to promote the repair of articular cartilage, due to its ability to differentiate into chondrocyte lineage as well as due to its paracrine effect to enhance the regenerative process. In spite of many early promising clinical results, the mechanism(s) underlying the immuno-modulative effect of MSC remain to be fully elucidated. The goal of the present study is to evaluate the paracrine effect of MSCs isolated from adipose tissue towards ATDC5 chondrogenic cells treated with and without IL-1β. In order to assess the paracrine effects of adipose-derived stem cells (ADSCs) and the related mechanism, a co-culture system was used. ATDC5 cells were treated with 10 ng/ml interleukin-1 (IL-1β), and/or co-cultured with mouse ADSCs. The study was divided into four groups: ATDC5 + IL-1β (group 1), ATDC5 only (group 2), ATDC5 + IL-1β + ADSCs (group 3), and ATDC5 + ADSCs (group 4). Flow cytometry, MTT assay, and real-time PCR were carried out. The result showed that isolated ADSCs highly expressed CD90, CD29, and CD105 and had a low expression of CD45. The cell viability of ATDC5 co-cultured with ADSCs was significantly higher than that of ATDC5 cultured alone. Similar results were obtained under IL-1β stimulation. The expression of MMP-3, MMP-9, MMP-13, LRP1, LRP5, LRP6, GSK3β, β-catenin, and Runx2 was significantly decreased when co-cultured with ADSCs. TIMP1 transcription was decreased by IL-1β and then slightly strengthened by co-culture with ADSCs, but without statistical significance. The results demonstrated that IL-1β-induced inflammation can be effectively relieved by the paracrine effect of ADSCs. The process may be, at least partly, regulated by the downregulation of the Wnt/β-catenin signaling pathway. Osteoarthritis (OA) is considered as a disease characterized by the destruction of the extracellular matrix and the loss of chondrocyte function, with inflammatory mediators released by cartilage, bone, and synovium. Modulating the immune cell response is essential to the repair/regenerative process. Nowadays, ADSCs are being increasingly considered for regenerative engineering use due to the ease of isolation from subcutaneous adipose tissue. A clear understanding of the paracrine effects of ADSCs on chondrogenic cells may lead to the development of novel therapeutic strategies for OA.