A novel model of adenine-induced tubulointerstitial nephropathy in mice

Abstract

BackgroundIn vivo models of uremia are important tools to study numerous aspects of acute and chronic kidney disease. Mouse models are pivotal because most genetically engineered animal models are mice, which allow dissecting the impact of selected target genes in renal failure. Adenine-based protocols to induce renal failure are available in rats, but have not been adapted in mice due to their reluctance to consume adenine. In the current paper we developed a novel method for induction of renal failure through dietary delivery of adenine mixed in a casein-based diet.ResultsAfter an induction phase, a stable model of renal impairment was obtained (target urea range 80–100 mg/dL), mimicking several aspects of chronic kidney disease - mineral and bone disorder including secondary hyperparathyroidism, bone abnormalities and pathological elevation of FGF23. No deaths occurred and the level of uremia was adaptable through adjustments of the adenine content, providing significant advantages compared to existing models. In an 8-week proof-of-concept study, renal histology showed mainly a tubulointerstitial damage with infiltrating leukocytes, interstitial edema and widening of the Bownman's space. Fibrosis was present in most animals as defined by histology and gene expression changes of fibrosis markers. Parathyroid cell proliferation was markedly increased but without signs of glandular hypertrophy. Skeletal histology showed increased trabecular bone and bone marrow adiposity whereas bone biomarkers (CTX and PINP) suggested higher bone formation, but surprisingly, lower bone resorption and perturbations in mineral metabolism.ConclusionsWe present a novel, non-surgical method for induction of renal failure in mice. This is an important complement to existing uremic models for pathophysiological studies in acute and chronic kidney disease, especially in terms of tubulointerstitial lesions.

Adenine-induced hyperphosphatemia in a murine model of renal insufficiency

“…Studies that have investigated adenine-induced renal dysfunction have reported phosphate status in mice; however, serum phosphate was not significantly different from control phosphate at all time points selected post-induction of dietary adenine, likely due to alternating dietary adenine inclusion between 0.15 and 0.20% over a 60 day period [15]. Hence we sought to develop an adenine model that minimized weight loss possibly due to feed refusal, resulted in low or no mortality, effectively induced permanent changes in phosphate status, and did not confound feed intake with several dietary additives (i.e., adenine plus test compounds to alleviate renal dysfunction).…”

“…Rats have been the model of choice for studying adenineinduced hyperphosphatemia, and the advantages of murine-based adenine models have been recently realized and reported by several investigators [2,15,16,21]. A reliable model of chemically-induced hyperphosphatemia in mice is useful since mice require less test compound and knockouts are widely available for studying basic mechanisms involving hyperphosphatemia.…”

“…Neither report evaluated the effects on blood phosphate status, a hallmark of human CKD. In a separate report, authors found that C57BL/6J mice fed 2% adenine in a casein-based diet had inconsistently increased serum phosphate over a d10-60 exposure period [15]. In a preliminary study in our laboratory, C57BL/6 male mice fed 0.25% or higher adenine showed outright food refusal within 3 days (3 g/day to <1 g/day, unpublished data).…”

“…Only recently have murine models of CKD employed the use of adenine; a desirable extension of the rat model due to ease of genetic manipulation and conservation of testable compounds [2,[13][14][15][16]. Male C57BL/6 mice supplemented with 0.25% adenine had an accumulation of collagen and 2,8-dihydroxyadenine in renal tubules and an accompanying macrophage infiltrate [13].…”

“…In a preliminary study in our laboratory, C57BL/6 male mice fed 0.25% or higher adenine showed outright food refusal within 3 days (3 g/day to <1 g/day, unpublished data). Previous reports using 0.20% dietary adenine did not report anorexia but did show significant weight loss by day 10 of feeding adenine compared to control mice [15]. Exposure to adenine through food may have secondary anorexia effects through food refusal and may confound the examination of diet-based therapies, hence gavage was selected to ensure a daily dose of adenine regardless of feed intake.…”