Construction of a CKD-MBD osteoporosis animal model using adenine combined with high-phosphorus diet at different time intervals and gradient concentrations

Recent advancements have led to the establishment of various animal models for chronic kidney disease-mineral and bone disorder (CKD-MBD), including 5/6 nephrectomy and drug induction. However, these models predominantly focus on kidney and vascular pathology, often neglecting skeletal lesions and exhibiting high mortality rates and unclear osteoporosis. Phosphorus plays a crucial role in bone metabolism, and prolonged high phosphorus intake can disrupt normal bone function. Our study introduces a novel CKD-MBD osteoporosis model using mice fed with adenine at three concentrations, combined with high phosphorus, zero calcium, and milk flavor, delivered in a time-segmented, stepwise descending manner. The 5/6 nephrectomy (5/6Nx) model served as the control group. Results indicated that the adenine group showed more pronounced pathological features of kidney function impairment, bone metabolism abnormalities, and histopathology compared to the 5/6Nx group. Serological analysis revealed elevated serum phosphorus, reduced serum calcium, and significant increases in parathyroid hormone, cystatin C, and β-crossLaps in the adenine group, suggesting more severe kidney damage and bone metabolism disorders. Kidney histology demonstrated greater fibrosis and severe focal inflammatory infiltration in the adenine group. Bone tissue analysis revealed increased osteoclast activity (tartrate-resistant acid phosphatase staining), upregulated CTSK expression, and significant osteoporosis (confirmed by dual-energy X-ray absorptiometry). Tunel staining indicated heightened apoptosis in the adenine group. Overall, the Adenine model effectively mirrors clinical symptoms of human kidney disease, aligning with human CKD stages IV-V. Compared to the 5/6Nx model, it offers advantages in reproducibility, mortality, operability, stability, and renal integrity, making it a promising candidate for further laboratory research.