MMP9 and Renal cyst: Decreased renal function in jck-MMP9-/- was due to the greater severity of renal lesions observed on histological sections (Fig 3A) as shown by an increase of the number of cysts (Fig 3B) and of the percentage of cystic kidney tissue in jck-MMP9 -/- compared to jck-MMP9+/+ mice (Fig 3C).