Comprehensive Evaluation of an Adenine/Phosphate-Induced CKD Model for the Study of Aortic Valve Calcification

Background: Calcific aortic valve disease (CAVD) is prevalent in chronic kidney disease (CKD), yet no pharmacological therapies exist. Preclinical models rarely incorporate CKD–mineral and bone disorder (CKD-MBD) features, limiting translational potential. We aimed to develop a comprehensive preclinical approach to study CKD-associated CAVD, suitable for standardized assessment of therapies on valvular, cardiac, vascular, and skeletal outcomes. Methods: Eight-week-old male Sprague Dawley rats were assigned to a control group (n=17) fed standard chow or an adenine-phosphate group (AP, n=21) fed chow supplemented with 0.3% adenine and 1.15% phosphate. Diets were enriched with 20% lactose and 19% casein to facilitate phosphate absorption and calcium solubility. Cardiac function was evaluated by echocardiography at baseline, week 5, and 9, with concurrent blood sampling. Aortic valve (AV) calcification was assessed by Alizarin Red and Osteosense staining, and aortic calcium quantified using O-Cresolphthalein Complexone. Gene expression in the aorta and left ventricle (LV) was analyzed by RNA-seq at week 9, and bone microarchitecture assessed by micro-CT. Results: AP rats showed progressive increases in serum creatinine, calcium-phosphorus product, and uremic toxins. By week 9, they exhibited significant AV calcification, with reduced valve area and cusp separation. Relative wall thickness and LV histology were preserved, though transcriptomics revealed early priming toward inflammation and fibrosis. AP rats’ aortas showed calcification, osteogenic features and reduced systolic expansion. Bone analysis revealed cortical thinning and increased porosity, while trabecular bone showed reduced trabecular number, increased trabecular spacing, and compensatory thickening. Together with elevated PTH and FGF23 levels, these changes suggest high bone turnover due to secondary hyperparathyroidism and are correlated with the extent of AV calcification. Conclusions: These results underscore the model’s translational relevance, addressing multiple facets of CKD-MBD and supporting its use for preclinical screening of novel therapies targeting CKD-associated cardiovascular calcification.