A highly reproducible mice model of chronic kidney disease: Evidences of behavioural abnormalities and blood-brain barrier disruption
Introduction
Chronic kidney disease (CKD) refers to a wide range of disease condition that affect the structure and function of the kidney, lasting for > 3 months, and leads to albuminuria and reduction in glomerular filtration rate (GFR) [7], [40]. The major causes for the development of CKD are diabetes, hypertension, glomerulonephritis and interstitial nephritis [7], [10]. There is an increase in the global prevalence of CKD, affecting > 15% of the population in developed nations [14], [17], [27]. With reduction in the GFR there occurs retention of uremic toxins and electrolyte imbalance [40], which necessitates, renal replacement therapies in the form of dialysis and kidney transplantation [44]. Due to retention of uremic toxins and electrolyte imbalance, CKD leads to cardiovascular disease, stroke [48], [49] and neurological complications (reviewed in Ref. [36]). In CKD patients, anxiety, depression, cognitive dysfunction, restless leg syndrome and reduced intelligence quotient are common diagnosis which hamper the quality of life [23], [28], [34], [36], [38], [39], [41], [60], [65]. In animal models, depression, anxiety and reduced exploratory and locomotor activities are reported [5], [16], [66].
One of the most widely used animal models of CKD is the surgical model [2], [21], [26], [37], [50]. However, owing to high mortality and need of sophisticated surgical methods, which alter the morphology of the animals as well, alternative models are sought. Yokozawa et al. [74] introduced rat model of CKD by administration of adenine with feed. Adenine and its metabolite (2,8-dihydroxyadenine) get deposited in renal tissues as crystals, as shown by Ikeda et al. [30] in rat model, and cause renal damages [5], [58], which leads to elevation in serum urea, creatinine and renal histological damage [9], [45], [62].
In rats with adenine-induced CKD, cardio-vascular damages have been investigated [22], while Ali et al. [5] reported on psycho-motor behavioural abnormalities. However, no behavioural study has been undertaken yet in mice model, and female mice have not yet been used as adenine-induced CKD model, to the best of our knowledge. In mice model of acute renal injury, disruption of blood-brain barrier (BBB) has been reported [42]. However, any such study is lacking in adenine-induced CKD model. In the present study, we induced CKD in adult female Swiss albino mice by administering high adenine diet. In this novel model, we investigated for renal fibrosis, psycho-motor behavioural abnormalities, neurological severity, BBB disruption, and histopathological changes in discrete brain regions.
Section snippets
Animals
Adult Swiss albino female mice of weight between 25 and 27 g (10 weeks old) were obtained from Pasteur Institute, Shillong, Meghalaya (India). They were housed in standard conditions of 12 h light/dark cycle, 24 ± 2 °C temperature and 60 ± 5% humidity; and were given standard feed and water ad libitum. An acclimatization time of 10 days was given prior to start of the experiment. The experimental protocols met the National Guidelines and were approved by the Institutional Animal Ethics Committee.
Chemicals and others
High adenine diet leads to decrease in body weight
Adenine, when given at 0.3% w/w mixed with feed for 4 weeks, leads to a significant reduction in body weight by 12.59% (compared to the initial body weight), while control mice (given standard feed) gained weight by 13.92% (Fig. 1A, B).
High adenine diet elevates serum urea and creatinine level
The level of serum urea has been found to be significantly higher in the adenine fed animals as compared to control (Fig. 1D). The treated mice had a mean urea level of 111.93 ± 2.40 mg/dL, while the control had 36.8 ± 0.56 mg/dL, thereby an increase of > 3-fold. The
Discussion
CKD is a global health issue with significant morbidity and mortality, and affects all levels of the nervous system (see Ref. [36]). However, detail study of the same are lacking in animal models, except the study by Ali et al. [5] in rat. In the present study, we established CKD in female Swiss albino mice by administering high adenine, and report on behavioural abnormalities (motor, psychometric and neurological severity) and BBB disruption.
The CKD mice model was generated by giving adenine
Conclusion
The present study reports development of a highly reproducible mice model of CKD induced by adenine feeding at the dose of 0.3% w/w mixed with diet for 4 weeks, having features of elevated serum urea and creatinine, and renal fibrosis. At this dose, deposition of adenine and 2,8-dihydroxyadenine crystals in renal tissues were observed. In this model, BBB disruption and behavioural abnormalities, including motor, psychometric and neurological severity, were found, which are reported hereby in
Conflict of interest
None declared.
Author contribution
MKM contributed by overall design of the experiment, performing the experiments, acquisition and interpretation of data, and drafting of the manuscript. AB contributed by conception of the idea and final approval of the manuscript. AG and SK contributed by revision of the manuscript.
Acknowledgment
We sincerely acknowledge the funding and support provided by the Department of Biotechnology (DBT), Govt. of India (under Rapid Grant for Young Investigator project; Sanction Order No. BT/PR6806/27/480/2012, dated August 05, 2013), and Department of Science and Technology, Govt. of India (Sanction Order No. SB/YS/LS-61/2014 dated March 04, 2015). MKM is recipient of Maulana Azad National Senior Research Fellowship from University Grant Commission, Govt. of India (MANF-2012-13-MUS-ASS-11201). We
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