Aims: Effective and applicable predictors of end-stage kidney disease (ESKD) are needed for patients with myeloperoxidase-antineutrophil cytoplasmic antibody-associated vasculitis (MPO-AAV) and kidney involvement. We investigated whether urinary matrix metalloproteinase-7 (uMMP7) was associated with kidney injury severity and incident ESKD in MPO-AAV. Results: A prospective two-stage study was conducted in 150 patients with newly diagnosed MPO-AAV in two independent cohorts. uMMP7 was measured on the days of initial and repeat kidney biopsies. In stage I, a higher initial uMMP7 level was associated with a lower estimated glomerular filtration rate (eGFR), higher level of proteinuria, and greater extent of kidney pathologic lesions. This elevated uMMP7 protein level is activated and potentially derived from the enhanced kidney production induced by oxidative stress. In stage II, uMMP7 at initial biopsy was independently associated with the incidence of ESKD over 6 years. The higher uMMP7 group (vs. lower) had an adjusted hazard ratio of 3.79 (95% confidence interval [CI], 1.49-6.09) for ESKD in the test cohort. Findings were similar in the validation cohort. A combination of data from the two cohorts revealed that adding uMMP7 into clinical or clinicopathologic models significantly improved risk discrimination for future ESKD. Innovation: An elevated uMMP7 level in MPO-AAV was independently associated with severe kidney injury and incident ESKD. Conclusions: uMMP7 in MPO-AAV improves identification of patients at risk of ESKD and may enable early and optimized therapy to improve outcomes. Antioxid. Redox Signal. 37, 246-256.
Keywords: MPO-AAV; end-stage kidney disease; kidney histologic injury; oxidative stress; urinary MMP7.