Epithelial Cell TGFβ Signaling Induces Acute Tubular Injury and Interstitial Inflammation

TGF beta signaling plays a central role in the development of acute and chronic kidney diseases. Previous in vivo studies involved systemic alteration of TGF beta signaling, however, limiting conclusions about the direct role of TGF beta in tubular cell injury. Here, we generated a double transgenic mouse that inducibly expresses a ligand-independent constitutively active TGF beta receptor type 1 (T beta R1) kinase specifically in tubular epithelial cells, with expression restricted by the Pax8 promoter. In this model, activation of TGF beta signaling in the tubular epithelium alone was sufficient to cause AKI characterized by marked tubular cell apoptosis and necrosis, oxidative stress, dedifferentiation and regenerative cell proliferation, reduced renal function, and interstitial accumulation of inflammatory cells. This tubular injury was associated with mitochondrial-derived generation of reactive oxygen species (ROS), but cell damage and apoptosis were partially independent of mitochondrial-derived ROS. T beta R1 signaling-induced tubular injury also associated with significant leukocyte infiltration consisting of F4/80(+) macrophages, CD11c(+) F4/80(+) dendritic cells, CD11c(+) F4/80(-) Ly6C(high) dendritic cells/monocytes, and T cells. Inhibition of mitochondrial-derived ROS significantly reduced accumulation of CD11c(+) F4/80(+) dendritic cells and T cells, suggesting a role for ROS in the activation and recruitment of the adaptive immune response to tubular injury. Taken together, these results suggest that TGF beta signaling in the tubular epithelium alone is sufficient to cause acute tubular injury and inflammation; therefore, TGF beta may be a mechanistic link between acute injury and chronic progression of kidney disease. J Am Soc Nephrol 24: 787-799, 2013. doi: 10.1681/ASN.2012101024