Neprilysin Knockout Attenuates Kidney Damage in a Rat Model of Renal Venous Congestion

Background: The kidneys and heart are closely connected known as the cardiorenal syndrome. Renal congestion caused by elevated central and renal venous pressures contributes to the progression of kidney injury. Neprilysin (MME) is an enzyme that degrades vasoactive peptides, including natriuretic peptides. Human atrial natriuretic peptide (hANP) is used therapeutically to treat acute heart failure. The role of MME in renal congestion remains unclear. In this study, we generated MME knockout (KO) rats using a genome editing technique and investigated the impact of MME deficiency in a rat model of renal congestion. Methods: The MME gene was knocked out in Sprague-Dawley rats using the rGONAD (rat Genome-editing via Oviductal Nucleic Acids Delivery) method. Renal congestion was induced in the left kidney of male MME knockout(KO) and wild-type (WT) rats by ligating the inferior vena cava between the renal veins. Three days after surgery, blood pressure was measured by the tail-cuff method. Both the left congested and right control kidneys were harvested and weighted. Real-time polymerase chain reaction (RT-PCR) and immunohistochemistry were performed. Plasma ANP concentrations were measured using ELISA. Results: MME immunostaining was observed in the proximal tubules of WT rats, while this was completely absent in MME KO rats. Blood pressure and plasma ANP levels were significantly lower in MME KO rats than in WT rats. The weight of the congested left kidney was increased in both MME KO and WT rats compared to the right control kidney. This increase was significantly attenuated in MME KO rats. RT-PCR and Western blotting revealed that increased expression of tubular injury markers (Kim1 and Opn), fibrosis markers (Acta2 and Fn1), and inflammation markers (CD68) in the left congested kidney compared to the right control kidney in both genotypes. The upregulation of these markers was suppressed in MME KO rats. Furthermore, immunohistochemical analysis showed reduced staining of αSMA and Kim1 in the congested kidneys of MME KO rats compared to WT rats. Conclusion: MME KO attenuated renal interstitial fibrosis and inflammation induced by renal venous congestion in rats, consistent with the known effects of natriuretic peptides. These findings suggest that MME inhibition may have a protective role against renal injury caused by venous congestion.