Antifibrotic TSG-6 Expression Is Synergistically Increased in Both Cells during Coculture of Mesenchymal Stem Cells and Macrophages via the JAK/STAT Signaling Pathway

The pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 beta upregulate TNF-alpha-stimulated gene 6 (TSG-6); however, current knowledge about the optimal conditions for TSG-6 expression in mesenchymal stem cells (MSCs) is limited. Here, we investigated whether TSG-6 expression varies depending on the polarization state of macrophages co-cultured with adipose tissue-derived stem cells (ASCs) and analyzed the optimal conditions for TSG-6 expression in ASCs. TSG-6 expression increased in ASCs co-cultured with M0, M1, and M2 macrophages indirectly; among them, M1 macrophages resulted in the highest increase in TSG-6 expression in ASCs. TSG-6 expression in ASCs dramatically increased by combination (but not single) treatment of TNF-alpha, IL-1 beta, interferon-gamma (IFN-gamma), and lipopolysaccharide (LPS). In addition, phosphorylation of signal transducer and activator of transcription (STAT) 1/3 was observed in response to IFN-gamma and LPS treatment but not TNF-alpha and/or IL-1 beta. STAT1/3 activation synergistically increased TNF-alpha/IL-1 beta-dependent TSG-6 expression, and JAK inhibitors suppressed TSG-6 expression both in ASCs and macrophages. In LX-2 hepatic stellate cells, TSG-6 inhibited TGF-beta-induced Smad3 phosphorylation, resulting in decreased alpha-smooth muscle actin (SMA) expression. Moreover, fibrotic activities of LX-2 cells induced by TGF-beta were dramatically decreased after indirect co-culture with ASCs and M1 macrophages. These results suggest that a comprehensive inflammatory microenvironment may play an important role in determining the therapeutic properties of ASCs by increasing TSG-6 expression through STAT1/3 activation.

Automated summary

This study investigated the expression of TSG-6 in mesenchymal stem cells and found that it is influenced by the polarization state of macrophages. Furthermore, it was discovered that TSG-6 expression is increased through STAT1/3 activation in an inflammatory microenvironment.