Given that MMP-9 expression was dysregulated in NRK-52E cells exposed to calcium, and that this effect was mediated by ROS levels and the NF-κB signaling pathway, we next performed an MMP-9 loss- and gain-of-function analysis using MMP-9 siRNA and an MMP-9 expression plasmid, respectively, to explore the role of this protein in kidney stone formation. The gene discussed is MMP9; the disease is nephrolithiasis.