['To determine whether matrix metalloproteinase-12 (MMP-12) plays a functional role in renal interstitial macrophage accumulation, interstitial fibrosis or tubular apoptosis in the unilateral ureteric obstruction (UUO) model.', 'MMP-12 is an enzyme that can cleave a number of extracellular matrix proteins and plays a role in macrophage-mediated injury in experimental models of emphysema and antibody-dependent glomerular disease. Macrophages are thought to promote renal fibrosis and tubular damage in the obstructed kidney. Furthermore, upregulation of MMP-12 expression by infiltrating macrophages in the obstructed kidney has been described, but the potential role of MMP-12 in renal injury induced by this non-immune insult is unknown.', 'Groups of eight MMP-12 gene deficient (MMP-12(-/-)) and wild type (WT) C57BL/6J mice were killed 3, 7 or 14 days after UUO.', 'Analysis of three different lineage markers found no difference in the degree of interstitial macrophage accumulation between MMP-12(-/-) and WT UUO groups at any time point. Examination of renal fibrosis by total collagen staining, α-SMA + myofibroblast accumulation, and TGF-β1, PAI-1 and collagen IV mRNA levels showed no difference between MMP-12(-/-) and WT UUO groups. Finally, tubular damage (KIM-1 levels) and tubular apoptosis (cleaved caspase-3) in the obstructed kidney was not affected by MMP-12 gene deletion.'] Are macrophage infiltration and renal damage independent of matrix metalloproteinase 12 in the obstructed kidney?