Whereas low levels of MMP-2, MMP-3, and MMP-9 could be detected by immufluorescence staining and immunoblotting in normal kidney tissue (Figure 2A–2C), MMP-2, MMP-3, and MMP-9 levels were significantly increased in kidneys obtained from patients with end-stage renal failure owing to XAS (Figure 2D–2L). This evidence concerns the gene MMP9 and stage 5 chronic kidney disease.