Msx2 is required for TNF-α-induced canonical Wnt signaling in 3T3-L1 preadipocytes

Tumor necrosis factor-α (TNF-α) is known to suppress adipocyte differentiation via a β-catenin-dependent pathway. However, the mechanisms by which TNF-α induces Wnt/β-catenin signaling pathway in adipocytes is unclear. Msx2, a homeobox transcription factor, is known to increase osteoblast differentiation through activation of the Wnt/β-catenin pathway. Therefore, in the present study, we investigated whether TNF-α activates the Wnt/β-catenin signaling pathway via the induction of Msx2 expression in 3T3-L1 preadipocytes. We found that TNF-α transiently increased Msx2 expression as well as the expression of canonical Wnt signaling molecules, including Wnt3a, Wnt7a, Wnt7b, Wnt10b, low-density lipoprotein receptor-related protein 5 (LRP5) and T-cell factor 1 (TCF1). Furthermore, TNF-α increased β-catenin/TCF-dependent transcriptional activity. To better understand the role of Msx2 in Wnt signaling, we examined the effects of Msx2 overexpression and knockdown on Wnt/β-catenin signaling. Msx2 overexpression alone significantly increased the levels of Wnt3a, Wnt7a, Wnt7b, Wnt10b, LRP5 and TCF1 expression, whereas knockdown of Msx2 using small interfering RNA prevented TNF-α-induced expression of Wnt signaling molecules. Taken together, the results of this study indicate that TNF-α enhances the Wnt/β-catenin signaling pathway by inducing Msx2 expression, which in turn suppresses adipocytic differentiation.