Enhanced expression of transforming growth factor-beta (TGF-β) in the kidneys of patients with lupus nephritis (LN) can lead to progressive fibrosis, resulting in end-organ damage. Disintegrin and metalloproteinases 9 (ADAM9) activate TGF-β1 by cleaving the latency-associated peptide (LAP). We hypothesized that ADAM9 in the kidney may accelerate fibrogenesis by activating TGF-β1.