B6-hXDH Mice

Catalog Number: C001586

Strain Name: C57BL/6NCya-Xdhtm1(hXDH)/Cya

Genetic Background: C57BL/6NCya

Reproduction: Homozygote x Homozygote

One of Cyagen's HUGO-GT™ (Humanized Genomic Ortholog for Gene Therapy) Mouse Strains

 

Strain Description

Hyperuricemia is a metabolic disorder characterized by abnormally elevated levels of uric acid (UA) in the blood. Uric acid, the end product of purine metabolism, may crystallize as urate in joints, leading to gouty arthritis or form stones in the kidneys when its concentration is excessively high. The clinical manifestations of gout include hyperuricemia, recurrent acute gouty arthritis, deposition of tophi, chronic tophaceous arthritis, and joint deformities. It commonly affects the kidneys, causing chronic interstitial nephritis and uric acid nephrolithiasis [1-3]. By 2020, the global prevalence of hyperuricemia and gout surpassed 1.1 billion cases. In China, the number of patients is projected to reach 200 million for hyperuricemia and 43.25 million for gout by 2024 [2-3]. With the increasing disease burden, the demand for pharmacological interventions for hyperuricemia and gout continues to grow.

Hyperuricemia is closely related to uric acid levels in the body, and current therapeutic agents mainly target the reduction of uric acid synthesis or the promotion of uric acid excretion to manage the condition. Xanthine oxidoreductase (XOR) plays a critical role in purine metabolism by catalyzing the oxidation of hypoxanthine to xanthine and subsequently to uric acid. It is thus a key regulatory point in uric acid synthesis and an important target for hyperuricemia treatment [4-5]. XOR exists in two forms: the reduced xanthine dehydrogenase (XDH) and the oxidized xanthine oxidase (XO). XDH, in its reduced state, catalyzes the conversion of hypoxanthine to xanthine and uric acid, generating reduced nicotinamide adenine dinucleotide (NADH). In contrast, XO, in its oxidized state, converts xanthine to uric acid and hydrogen peroxide. The inhibition of XO by xanthine oxidase inhibitors (XOIs) to reduce uric acid production is a widely adopted therapeutic strategy for hyperuricemia and gout [6]. However, safety concerns remain with existing XOIs, highlighting the urgent need for novel therapeutics with improved safety profiles. Small interfering RNA (siRNA) represents a promising research focus in this area.

This strain is a humanized mouse model of the Xdh gene, generated by replacing the mouse Xdh gene with the complete human XDH gene sequence, including its untranslated regions (UTRs), exons, and introns. The B6-hXDH mice express the human XDH gene and xanthine oxidase protein in a pattern similar to the endogenous Xdh gene in mice, making their genetic, protein expression, and biochemical features highly comparable to humans. This strain serves as an ideal preclinical platform for studying the pathological mechanisms of hyperuricemia and gout and for developing novel xanthine oxidase inhibitors and nucleic acid therapies.

Strain Strategy


Figure 1. Schematic representation of gene targeting in B6-hXDH mice. Gene-editing technology was used to replace the mouse Xdh sequence (from 5'UTR to 3'UTR) with the corresponding sequence from the human XDH gene.

 

Application

This strain is suitable for investigating the pathological mechanisms of hyperuricemia and gout, as well as for screening, developing, and evaluating the efficacy of targeted therapies.

 

Validation Data

1. Gene Expression Detection


Figure 2. Comparison of XDH gene expression between wild-type (WT) and B6-hXDH mice across tissues (6 weeks old). RT-qPCR analysis revealed human XDH gene expression in the colon, kidney, and liver of B6-hXDH mice, with no detectable expression of the endogenous mouse Xdh gene. The expression pattern of the human XDH gene in B6-hXDH mice was similar to that of the endogenous mouse Xdh gene in WT mice (Bars represent mean ± SEM, n=3).
ND: Not detected.

2. Protein Expression Detection


Figure 3. Detection of human xanthine oxidase protein in the liver and kidney of WT and B6-hXDH mice*. Western blot analysis confirmed the expression of human xanthine oxidase protein in B6-hXDH mice.
*Note: The antibody used was cross-reactive for both mouse and human proteins, resulting in bands in WT mice. However, RT-qPCR results confirmed the absence of mouse Xdh mRNA and the exclusive expression of human XDH mRNA in B6-hXDH mice.

3. Serum Uric Acid (UA) and Blood Urea Nitrogen (BUN) Levels


Figure 4. Serum levels of uric acid (UA) and blood urea nitrogen (BUN) in WT and B6-hXDH mice (6 to 7 weeks old). Biochemical analysis showed slightly lower serum UA levels in B6-hXDH mice compared to WT mice, with a more pronounced difference in male mice. No significant differences in serum BUN levels were observed between the two groups (Bars represent mean ± SEM, n=5).

References
[1]Du L, Zong Y, Li H, Wang Q, Xie L, Yang B, Pang Y, Zhang C, Zhong Z, Gao J. Hyperuricemia and its related diseases: mechanisms and advances in therapy. Signal Transduct Target Ther. 2024 Aug 28;9(1):212.
[2]Dalbeth N, Choi HK, Joosten LAB, Khanna PP, Matsuo H, Perez-Ruiz F, Stamp LK. Gout. Nat Rev Dis Primers. 2019 Sep 26;5(1):69.
[3]Dalbeth N, Gosling AL, Gaffo A, Abhishek A. Gout. Lancet. 2021 May 15;397(10287):1843-1855. doi: 10.1016/S0140-6736(21)00569-9. Epub 2021 Mar 30. Erratum in: Lancet. 2021 May 15;397(10287):1808.
[4]Furuhashi M. New insights into purine metabolism in metabolic diseases: role of xanthine oxidoreductase activity. Am J Physiol Endocrinol Metab. 2020 Nov 1;319(5):E827-E834. 
[5]Bortolotti M, Polito L, Battelli MG, Bolognesi A. Xanthine oxidoreductase: One enzyme for multiple physiological tasks. Redox Biol. 2021 May;41:101882.
[6]Lee Y, Hwang J, Desai SH, Li X, Jenkins C, Kopp JB, Winkler CA, Cho SK. Efficacy of Xanthine Oxidase Inhibitors in Lowering Serum Uric Acid in Chronic Kidney Disease: A Systematic Review and Meta-Analysis. J Clin Med. 2022 Apr 27;11(9):2468.