Spontaneous calcified tongue lesions in DBA mice

Identification of a DBA/2 Mouse Sub-strain as a Model for Pseudoxanthoma Elasticum-Like Tissue Calcification

Ectopic calcification in the cardiovascular system adversely affects life prognosis. DBA/2 mice experience calcification owing to low expression of Abcc6 as observed in pseudoxanthoma elasticum (PXE) patients; however, little is known about its characteristics as a calcification model. In this study, we explore the suitability of a DBA/2 sub-strain as a PXE-like tissue calcification model, and the effect of a bisphosphonate which prevents calcification of soft tissues in hypercalcemic models was evaluated. The incidence of calcification of the heart was compared among several sub-strains and between both sexes of DBA/2 mice. mRNA expression of calcification-related genes was compared with DBA/2 sub-strains and other mouse strains. In addition, progression of calcification and calciprotein particle formation in serum were examined. Among several sub-strains of DBA/2 mice, male DBA/2CrSlc mice showed the most remarkable cardiac calcification. In DBA/2CrSlc mice, expression of the anti-calcifying genes Abcc6, Enpp1 and Spp1 was lower than that in C57BL/6J, and expression of Enpp1 and Spp1 was lower compared with other sub-strains. Calcification was accompanied by accelerated formation of calciprotein particle, which was prevented by daily treatment with bisphosphonate. A model suitable for ectopic calcification was identified by choosing a sub-strain of DBA/2 mice, in which genetic characteristics would contribute to extended calcification.

Tryptophan Pathway Abnormalities in a Murine Model of Hereditary Glaucoma

Background: It has been shown that a possible pathogenetic mechanism of neurodegeneration in the mouse model of glaucoma (DBA/2J) may be an alteration of kynurenic acid (KYNA) in the retina. This study aimed to verify the hypothesis that alterations of tryptophan (TRP) metabolism in DBA/2J mice is not limited to the retina. Methods: Samples of the retinal tissue and serum were collected from DBA/2J mice (6 and 10 months old) and control C57Bl/6 mice of the same age. The concentration of TRP, KYNA, kynurenine (KYN), and 3-hydroxykynurenine (3OH-K) was measured by HPLC. The activity of indoleamine 2,3-dioxygenase (IDO) was also determined as a KYN/TRP ratio. Results: TRP, KYNA, L-KYN, and 3OH-K concentration were significantly lower in the retinas of DBA/2J mice than in C57Bl/6 mice. 3OH-K concentration was higher in older mice in both strains. Serum TRP, L-KYN, and KYNA concentrations were lower in DBA/2J than in age-matched controls. However, serum IDO activity did not differ significantly between compared groups and strains. Conclusions: Alterations of the TRP pathway seem not to be limited to the retina in the murine model of hereditary glaucoma.

Differential Expression of Hypertensive Phenotypes in BXD Mouse Strains in Response to Angiotensin II

BACKGROUND

Besides environmental risk factors, genetic factors play a crucial role in the pathogenesis of primary hypertension. The current study is to unravel whether hypertensive phenotypes vary in mice with different genetic background.

METHODS

Hypertension was induced in C57BL/6J (B6), DBA/2J (D2), and 25 BXD strains by administrating angiotensin (Ang)II (2.5 mg/kg/day infused by osmotic minipump) for 4 weeks. Systolic blood pressure was monitored before (baseline) and after 4 weeks of AngII treatment by tail cuff. Cardiac and renal fibrosis was evaluated by picrosirius red staining and collagen volume fraction (CVF) was quantitated using imaging analyzing system; cardiac transforming growth factor (TGF)-β gene expression was monitored by RT-PCR, and inflammatory response was detected by immunohistochemical ED-1 staining.

RESULTS

AngII infusion caused hypertension in all strains. However, blood pressure elevation was more evident in the D2 strain than the B6 group, while it was widely variable among BXD strains. Furthermore, chronic AngII treatment lead to development of hypertensive cardiac and renal diseases. Cardiac and renal CVF levels in the D2 strain was significantly higher than the B6 cohort, whereas these varied vastly across BXD strains. Moreover, cardiac TGF-β mRNA levels were markedly diverse among various mouse strains.

CONCLUSION

Our study unequivocally demonstrates that in response to AngII, BXDs with different genetic background expressed hypertension phenotypes with varied degree in severity. It implicates that genomics contribute to pathogenesis of primary hypertension. Building upon the genotype and hypertensive phenotypes, the BXD cohort can be further exploited experimentally to identify genes that influence blood pressure.

A Murine Hypertrophic Cardiomyopathy Model: The DBA/2J Strain

Familial hypertrophic cardiomyopathy (HCM) is attributed to mutations in genes that encode for the sarcomere proteins, especially Mybpc3 and Myh7. Genotype-phenotype correlation studies show significant variability in HCM phenotypes among affected individuals with identical causal mutations. Morphological changes and clinical expression of HCM are the result of interactions with modifier genes. With the exceptions of angiotensin converting enzyme, these modifiers have not been identified. Although mouse models have been used to investigate the genetics of many complex diseases, natural murine models for HCM are still lacking. In this study we show that the DBA/2J (D2) strain of mouse has sequence variants in Mybpc3 and Myh7, relative to widely used C57BL/6J (B6) reference strain and the key features of human HCM. Four-month-old of male D2 mice exhibit hallmarks of HCM including increased heart weight and cardiomyocyte size relative to B6 mice, as well as elevated markers for cardiac hypertrophy including β-myosin heavy chain (MHC), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and skeletal muscle alpha actin (α1-actin). Furthermore, cardiac interstitial fibrosis, another feature of HCM, is also evident in the D2 strain, and is accompanied by up-regulation of type I collagen and α-smooth muscle actin (SMA)-markers of fibrosis. Of great interest, blood pressure and cardiac function are within the normal range in the D2 strain, demonstrating that cardiac hypertrophy and fibrosis are not secondary to hypertension, myocardial infarction, or heart failure. Because D2 and B6 strains have been used to generate a large family of recombinant inbred strains, the BXD cohort, the D2 model can be effectively exploited for in-depth genetic analysis of HCM susceptibility and modifier screens.