A STAT5-Smad3 dyad regulates adipogenic plasticity of visceral adipose mesenchymal stromal cells during chronic inflammation.

Adipogenic differentiation of visceral adipose tissue-resident multipotent mesenchymal stromal cells (VA-MSC) into adipocytes is metabolically protective. Under chronic inflammatory stress, this neoadipogenesis process is suppressed by various pro-inflammatory cytokines and growth factors. However, the underlying mechanism(s) regulating VA-MSC plasticity remains largely unexplored. Using an adipogenic differentiation screen, we identified IFNγ and TGFβ as key inhibitors of primary human VA-MSC differentiation. Further studies using human and mouse VA-MSCs and a chronic high-fat diet-fed murine model revealed that IFNγ/JAK2-activated STAT5 transcription factor is a central regulator of VA-MSC differentiation under chronic inflammatory conditions. Furthermore, our results indicate that under such conditions, IFNγ-activated STAT5 and TGFβ-activated Smad3 physically interact via Smad4. This STAT5-Smad4-Smad3 complex plays a crucial role in preventing the early adipogenic commitment of VA-MSCs by suppressing key pro-adipogenic transcription factors, including CEBPδ, CEBPα, and PPARγ. Genetic or pharmacological disruption of IFNγ-TGFβ synergy by inhibiting either STAT5 or Smad3 rescued adipogenesis under chronic inflammatory stress. Overall, our study delineates a central mechanism of MSC plasticity regulation by the convergence of multiple inflammatory signaling pathways.