Additionally, the expression of atrial natriuretic peptide (Nppa) in the LV, a marker of myocardial stretch, showed an increasing tendency (p = 0.083), and the collagenase matrix metalloprotease-9 (Mmp9) was significantly overexpressed in the CKD-only group compared to the sham group (Fig. 4d and e). This evidence concerns the gene MMP9 and chronic kidney disease.