MST1/2 in PDGFRα+ cells negatively regulates TGF-ß-induced myofibroblast accumulation in renal fibrosis.

Injury-induced fibroblast-to-myofibroblast differentiation is a key event of renal fibrosis. Yes-associated protein (YAP), a transcriptional coactivator, plays an important role in fibroblast activation and Smad transcriptional activity to promote transforming growth factor-ß (TGF-ß)-induced differentiation from fibroblasts to myofibrolasts. Macrophage stimulating 1/2 (MST1/2), a negative regulator of YAP, also increases in fibroblasts by TGF-ß stimulation. Here, we examined whether MST1/2, as a negative regulator, attenuated YAP and TGF-ß/Smad signaling in fibroblasts to reduce fibrosis. MST1/2 and YAP expression levels increased in platelet-derived growth factor receptor-α (PDGFRα)+ cells of obstructed kidneys following the increase of TGF-ß and renal fibrosis after unilateral ureteral obstruction. PDGFRα+ cell-specific knockout of Mst1/2 in mice increased unilateral ureteral obstruction-induced myofibroblast accumulation and fibrosis. In cultured fibroblasts, TGF-ß increased YAP and promoted its nucleus entry, but a high dose and prolonged treatment of TGF-ß increased the MST1/2 activation to prevent YAP from entering the nucleus. Our results indicate that MST1/2 is a negative feedback signal of TGF-ß-induced fibroblast differentiation.NEW & NOTEWORTHY Using a mouse model with macrophage stimulating 1/2 (Mst1/2) double knockout in PDGFRα+ cells and an MST1/2 inhibitor, we demonstrated that MST1/2 acted as a negative feedback signal of transforming growth factor-ß-induced fibroblast differentiation. Furthermore, we demonstrated that Hippo-MST as a negative feedback signal can decrease the renal fibrosis process. This finding contributes to our understanding of the mechanism of coregulated renal remodeling after injury.

The Mechanism of CD8+ T Cells for Reducing Myofibroblasts Accumulation during Renal Fibrosis.

Renal fibrosis is a hallmark of chronic kidney disease (CKD) and a common manifestation of end-stage renal disease that is associated with multiple types of renal insults and functional loss of the kidney. Unresolved renal inflammation triggers fibrotic processes by promoting the activation and expansion of extracellular matrix-producing fibroblasts and myofibroblasts. Growing evidence now indicates that diverse T cells and macrophage subpopulations play central roles in the inflammatory microenvironment and fibrotic process. The present review aims to elucidate the role of CD8+ T cells in renal fibrosis, and identify its possible mechanisms in the inflammatory microenvironment.