Uricase-deficient rat is generated with CRISPR/Cas9 technique

Abstract

Urate oxidase (uricase, Uox) is a big obstacle for scientists to establish stable animal models for studying hyperuricemia and associated disorders. Due to the low survival rate of uricase-deficient mice, we generated a Uox-knockout model animal from Sprague Dawley (SD) rats using the CRISPR/Cas9 technique by deleting exons 2 to 4 of the Uox gene. The uricase-deficient rats were named “Kunming-DY rats”, and were apparently healthy with more than a 95% survival up to one year. The male rats’ serum uric acid (SUA) increased to 48.3 ± 19.1 µg/ml, significantly higher than those of wild-type rats. Some indexes of the blood fat like total triglyceride, low density lipoprotein, and renal function indexes including blood urea nitrogen and serum creatinine were significantly different from those of wild-type rats, however, all the indexes were close to or in normal ranges. Histological renal changes including mild glomerular/tubular lesions were observed in these uricase-deficient rats. Thus, “Kunming-DY rats” with stable uricase-deficiency were successfully established and are an alternative model animal to study hyperuricemia and associated diseases mimicking human conditions.

Aboriginal Bacterial Flora in the Uricase-Deficient Rat Gut is Not the Main Factor Affecting Serum Uric Acid

“…SCXK (Chuan) 2008–24). Uox −/− (Kunming-DY) and wild-type rats of the same age (45 days old) were generated in our laboratory as previously described [ 9 ].…”

“…Breeding. Uox -/rats were generated, identified, and raised in our laboratory as previously described [9]. Briefly, the male Uox -/rats were mated with the female Uox -/rats for three weeks to generate their offspring.…”

“…Furthermore, most experiments on lowering the SUA levels by affecting bacteria were carried out in animals who expressed uricase [ 2 – 4 , 7 , 8 ]. In order to exclude the tangling factor of the host's uricase, uricase-deficient (Uox −/− ) rats were generated by our team on the background of Sprague–Dawley (SD) rats; they were named “Kunming-DY rats” [ 9 ], a type of closed colony animals rather than inbred animals, such as C57BL/6J [ 10 , 11 ]. Different from Uox −/− mice [ 10 , 11 ], the SUA level in the male Uox −/− rats was about 48.3 ± 19.1 μ g/ml [ 9 ], which significantly increased but still much lower than that in Uox −/− mice.…”

“…In order to exclude the tangling factor of the host's uricase, uricase-deficient (Uox −/− ) rats were generated by our team on the background of Sprague–Dawley (SD) rats; they were named “Kunming-DY rats” [ 9 ], a type of closed colony animals rather than inbred animals, such as C57BL/6J [ 10 , 11 ]. Different from Uox −/− mice [ 10 , 11 ], the SUA level in the male Uox −/− rats was about 48.3 ± 19.1 μ g/ml [ 9 ], which significantly increased but still much lower than that in Uox −/− mice. Since the level of SUA in the Uox −/− rats was similar to that in men, it has been suggested that the rats could be one of the optimal animals to study gout and associated diseases.…”

Modulation of Urate Transport by Drugs

“…Kunming rats were healthy with more than 95% survival up to one year. Mean SU in male Kunming rats was 48.3 µg/mL, significantly higher compared to wild-type male Sprague-Dawley rats (under 20 µg/mL in the study) [ 78 ]. In the rat model of fructose-induced hyperuricemia, treatment with uricase-expressing engineered bacteria significantly decreased serum urate levels [ 79 ], supporting the notion that exogenous uricase may improve hyperuricemia.…”