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Understanding longitudinal biventricular structural and functional changes in a pulmonary hypertension Sugen-hypoxia rat model by cardiac magnetic resonance imaging.

ABSTRACT: Cardiac magnetic resonance-derived ventricular variables are predictive of mortality in pulmonary arterial hypertension. Rodent models which emphasize ventricular function, allowing serial monitoring, are needed to identify pathophysiological features and novel therapies for pulmonary arterial hypertension. We investigated longitudinal changes in the Sugen-hypoxia model during disease progression. Sprague Dawley rats (n?=?32) were divided into two groups. (1) Sugen-hypoxia: a dose of subcutaneous Sugen-5416 and placed in hypobaric hypoxia for two weeks followed by normoxia for three weeks. (2) Normoxia: maintained at normal pressure for five weeks. Rats were examined at five or eight weeks with right-heart catheter, cardiac magnetic resonance, and autopsy. Compared to normoxic controls (23.9?±?4.1?mmHg), right ventricular systolic pressure was elevated in Sugen-hypoxia rats at five and eight weeks (40.9?±?15.5?mmHg, p?=?0.026; 48.9?±?9.6?mmHg, p?=?0.002). Right ventricular end-systolic volume index was increased in eight weeks Sugen-hypoxia (0.28?±?0.04 µlcm-2, p?=?0.003) compared to normoxic controls (0.18?±0.03?mlcm-2). There was progressive dilatation of the right ventricular at eight weeks Sugen-hypoxia compared to normoxic controls (0.75?±?0.13 µlcm-2 vs 0.56?±?0.1 µlcm-2 p?=?0.02). Ventricle mass index by cardiac magnetic resonance at five weeks (0.34?±?0.06, p?=?0.003) and eight weeks Sugen-hypoxia (0.34?±?0.06, p?=?0.002) were higher than normoxic controls (0.21?±?0.04). Stroke volume, right ventricular ejection fraction, and left ventricular variables were preserved in Sugen-hypoxia. Ventricular changes during the course of illness in a pulmonary arterial hypertension rodent model can be examined by cardiac magnetic resonance. These changes including right ventricular hypertrophy and subsequent dilatation are similar to those seen in pulmonary arterial hypertension patients. Despite the persisting pulmonary hypertension, there are features of adaptive cardiac remodeling through the study duration.

SUBMITTER: Jayasekera G

PROVIDER: S-EPMC7011361 | biostudies-literature | 2020 Jan-Mar

REPOSITORIES: biostudies-literature

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Understanding longitudinal biventricular structural and functional changes in a pulmonary hypertension Sugen-hypoxia rat model by cardiac magnetic resonance imaging.

Jayasekera Geeshath G Wilson Kathryn S KS Buist Hanna H Woodward Rosemary R Uckan Aysel A Hughes Colin C Nilsen Margaret M Church A Colin AC Johnson Martin K MK Gallagher Lindsay L Mullin James J MacLean Mandy R MR Holmes William M WM Peacock Andrew J AJ Welsh David J DJ

Pulmonary circulation 20200101 1

Cardiac magnetic resonance-derived ventricular variables are predictive of mortality in pulmonary arterial hypertension. Rodent models which emphasize ventricular function, allowing serial monitoring, are needed to identify pathophysiological features and novel therapies for pulmonary arterial hypertension. We investigated longitudinal changes in the Sugen-hypoxia model during disease progression. Sprague Dawley rats (<i>n</i> = 32) were divided into two groups. (1) Sugen-hypoxia: a dose of subc ...[more]

PMID: 32095230

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Project description:Pulmonary vasoreactivity could determine the responsiveness to vasodilators and, in turn, the prognosis of pulmonary hypertension (PH). We hypothesized that pulmonary vasoreactivity is impaired, and we examined the underlying mechanisms in the Sugen-hypoxia rat model of severe PH. Male Sprague-Dawley rats were injected with Sugen (20 mg/kg s.c.) and exposed to hypoxia (9% O2) for 3 weeks, followed by 4 weeks in normoxia (Su/Hx), or treated with Sugen alone (Su) or hypoxia alone (Hx) or neither (Nx). After hemodynamic measurements, the heart was assessed for right ventricular hypertrophy (Fulton's index); the pulmonary artery, aorta, and mesenteric arteries were isolated for vascular function studies; and contractile markers were measured in pulmonary arteries using quantitative polymerase chain reaction (PCR). Other rats were used for morphometric analysis of pulmonary vascular remodeling. Right ventricular systolic pressure and Fulton's index were higher in Su/Hx versus Su, Hx, and Nx rats. Pulmonary vascular remodeling was more prominent in Su/Hx versus Nx rats. In pulmonary artery rings, contraction to high KCl (96 mM) was less in Su/Hx versus Nx and Su, and phenylephrine-induced contraction was reduced in Su/Hx versus Nx, Hx, and Su. Acetylcholine (ACh)-induced relaxation was less in Su/Hx versus Nx and Hx, suggesting reduced endothelium-dependent vasodilation. ACh relaxation was inhibited by nitric oxide synthase (NOS) and guanylate cyclase blockade in all groups, suggesting a role of the NO-cGMP pathway. Nitrate/nitrite production in response to ACh was less in Su/Hx versus Nx, supporting reduced endothelial NO production. Sodium nitroprusside (10-8 M) caused less relaxation in Su/Hx versus Nx, Hx, and Su, suggesting a decreased responsiveness of vascular smooth muscle (VSM) to vasodilators. Neither contraction nor relaxation differed in the aorta or mesenteric arteries of all groups. PCR analysis showed decreased expression of contractile markers in pulmonary artery of Su/Hx versus Nx. The reduced responsiveness to vasoconstrictors and NO-mediated vasodilation in the pulmonary, but not systemic, vessels may be an underlying mechanism of severe PH in Su/Hx rats and appears to involve attenuation of the NO relaxation pathway and a switch of pulmonary VSM cells to a synthetic less reactive phenotype.

Dataset Information

Understanding longitudinal biventricular structural and functional changes in a pulmonary hypertension Sugen-hypoxia rat model by cardiac magnetic resonance imaging.

Publications

Understanding longitudinal biventricular structural and functional changes in a pulmonary hypertension Sugen-hypoxia rat model by cardiac magnetic resonance imaging.

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