Apelin Inhibits Cyst Growth and Improves Kidney Function in Mice with Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disorder marked by numerous renal cysts that impair kidney function, with about half of affected individuals progressing to kidney failure by midlife. Patients exhibit reduced circulating apelin, a ligand of the apelin receptor known to regulate cardiovascular function including hypertension. We tested whether diminished apelin signaling contributes to cystogenesis and if exogenous apelin receptor activation can improve disease outcomes.

Plasma samples from children and young adults with ADPKD and age- and sex-matched healthy controls were analyzed for circulating apelin peptides. To assess direct cystic effects, primary ADPKD renal epithelial cells were grown as 3D collagen-embedded cysts and treated with apelin agonists. Male and female Pkd1RC/RC; Pkd2+/- (PKD) mice were treated for 27 days with apelin agonists, vehicle, or the vasopressin receptor antagonist, mozavaptan. Kidney and heart weight ratios, BUN, renal cAMP, and kidney transcriptional profiles were evaluated.

Circulating apelin peptides were significantly reduced in ADPKD patients despite normal kidney function (eGFR, BUN, and creatinine). In vitro, both apelin and the small molecule apelin receptor agonist, azelaprag, inhibited cyst growth. Apelin and mozavaptan reduced kidney weight, cystic index, blood urea nitrogen and renal cAMP in PKD mice, whereas azelaprag did not. Apelin downregulated expression of genes associated with cyst progression, including Lcn2 (Ngal), Postn, and Havcr1 (Kim-1). Mozavaptan, but not apelin, induced diuresis and reduced urinary concentration.

Apelin receptor activation by exogenous apelin inhibited cAMP synthesis and cyst growth and improved kidney function in an orthologous mouse model of ADPKD. We propose that the apelin receptor may be a potential therapeutic target in ADPKD.