A Model of Left Ventricular Dysfunction Complicated by CAWS Arteritis in DBA/2 Mice

Abstract

It was reported previously that a Candida albicans water-soluble fraction (CAWS), including a mannoprotein and β-glucan complex, has strong potency in inducing fatal necrotizing arteritis in DBA/2 mice. In this study, histopathological changes and cardiac function were investigated in this system. One mg/day of CAWS was given to DBA/2 mice via peritoneal injection for five days. The CAWS-treated DBA/2 mice were induced aortitis and died at an incidence of 100% within several weeks. Histological findings included stenosis in the left ventricular outflow tract (LVOT) and severe inflammatory changes of the aortic valve with fibrinoid necrosis. Cardiomegaly was observed and heart weight increased 1.62 fold (P < 0.01). Echocardiography revealed a severe reduction in contractility and dilatation of the cavity in the left ventricle (LV): LV fractional shortening (LVFS) decreased from 71% to 38% (P < 0.01), and the LV end-diastolic diameter (LVDd) increased from 2.21 mm to 3.26 mm (P < 0.01). The titer of BNP mRNA increased in the CAWS-treated group. Severe inflammatory changes resulting from CAWS brought about lethal LV dysfunction by aortic valve deformation with LVOT stenosis. This system is proposed as an easy and useful experimental model of heart failure because CAWS arteritis can be induced by CAWS injection alone.

Figure 1

Kaplan-Meier analysis of CAWS arteritis in DBA/2 mice. CAWS treatment DBA/2 mice were administered with CAWS one mg/mouse via peritoneal injections for five consecutive days. DBA/2 mice at four or five weeks of age were maintained in specific pathogen free (SPF) conditions and observed every day. All CAWS treatment mice died between five and eight weeks after treatment. P < 0.005 for survival of untreated versus CAWS treatment mice at six weeks after the CAWS treatment; n = 8 (control) and n = 10 (CAWS treatment).

Figure 2

CAWS arteritis development and progress in DBA/2 mice. Cardiovascular tissue was sampled every week after CAWS administration, and induced aortitis was observed with an incidence of 100%. The first week panel (a, b—1w) shows slight aortic valve thickening and endocardial inflammation of the Valsalva sinuses; left coronary (LC) sinus, right coronary (RC) sinus, and noncoronary (NC) sinus. The second week panel (a, b—2w) shows expansion of the severe inflammatory lesion around the left coronary arteries (LCA). The third and fourth week panels (a, b—3w and 4w) show the features of the necrosis-related vasculitis. Inflammatory cells have spread to all the layers and sinuses with fibrinoid necrosis in the elastic lamina (arrows). Severe stenosis was found in coronary arteries because of inflammatory cells accumulation.

Figure 3

The tissue image of the CAWS arteritis by electron microscope. The images demonstrated direct invasion to the elastic fiber (a) and the activated inflammatory cells accumulation in the abscess-like lesion (b).

Figure 4

Cardiomegaly and histopathological changes of the aortic root due to CAWS arteritis. Macroscopic cardiomegaly and concentric left ventricular hypertrophy were observed in the CAWS treatment group (a, b). The panels (c) represent enlarged views of each aortic valve. Inflammatory cells were located mainly in the aortic valve and Valsalva sinus, and severe stenosis of the left ventricular outflow tract (LVOT) was found in CAWS arteritis. There was no evidence of necrosis or fibrosis to indicate broad infarctions in the left ventricular wall. The cross sectional area of CAWS-treated cardiomyocyte was increased by 1.14 fold (d).

Figure 5

Heart weight and time course of body weight in CAWS arteritis. (a) The column graph represents the heart weight (HW)/body weight (BW) ratio, which increased significantly by 1.62-fold (P < 0.01); n = 8 (untreated) and n = 7 (CAWS treatment). (b) The time course of body weight with/without CAWS treatment DBA/2 mice.

Figure 6

Comparison of the cardiac function measured by echocardiography in untreated and CAWS treatment DBA/2 mice. CAWS treatment DBA/2 mice developed left ventricular dilution and dysfunction between six and seven week after CAWS administration (a). Echocardiography revealed a diffuse, severe reduction of contractility in the left ventricle after CAWS treatment. Left ventricular fractional shortening (LVFS) decreased from 71% to 38% (P < 0.01), and dilation of the left ventricular diastolic dimension (LVDd) was observed from 2.21 mm to 3.26 mm (P < 0.01) (b); n = 10 (untreated) and n = 6 (CAWS treatment).

Figure 7

mRNA expression of murine BNP in CAWS arteritis. The cDNA levels of murine BNP were examined by RT-PCR and found to be increased.

Figure 8

Summarized time course of CAWS-induced systemic inflammation and vasculitis.