Matrix Metalloproteinase-7 as a Surrogate Marker Predicts Renal Wnt/β-Catenin Activity in CKD

A variety of chronic kidney diseases exhibit reactivation of Wnt/beta-catenin signaling. In some tissues, beta-catenin transcriptionally regulates matrix metalloproteinase-7 (MMP-7), but the association between MMP-7 and Wnt/beta-catenin signaling in chronic kidney disease is unknown. Here, in mouse models of both obstructive nephropathy and focal segmental glomerulosclerosis (adriamycin nephropathy), we observed upregulation of MMP-7 mRNA and protein in a time-dependent manner. The pattern and extent of MMP-7 induction were positively associated with Wnt/beta-catenin signaling in these models. Activation of beta-catenin through ectopic expression of Wnt1 promoted MMP-7 expression in vivo, whereas delivery of the gene encoding the endogenous Wnt antagonist Dickkopf-1 abolished its induction. Levels of MMP-7 protein detected in the urine correlated with renal Wnt/beta-catenin activity. Pharmacologic blockade of Wnt/beta-catenin signaling by paricalcitol inhibited MMP-7 expression in diseased kidneys and reduced the levels detected in the urine. In vitro, beta-catenin activation induced the expression and secretion of MMP-7 and promoted the binding of T cell factor to the MMP-7 promoter in kidney epithelial cells. We also observed higher levels of MMP-7 expression, which correlated with beta-catenin, in kidney tissue from patients with various nephropathies. In summary, levels of renal MMP-7 correlate with Wnt/beta-catenin activity, and urinary MMP-7 may be a noninvasive biomarker of this profibrotic signaling in the kidney.