SMAD7 and renal fibrosis: TFPI2, a Kunitz-type serine proteinase inhibitor family member primarily produced by endothelial cells originating from various blood vessels, contributes to diabetic nephropathy progression by facilitating renal fibrosis and EMT through the modulation of the SMURF2/SMAD7-mediated TGF-β/Smad signaling pathway [75].