Large animal models of pressure overload-induced cardiac left ventricular hypertrophy to study remodelling of the human heart with aortic stenosis

Pathologic cardiac hypertrophy is a common consequence of many cardiovascular diseases, including aortic stenosis (AS). AS is known to increase the pressure load of the left ventricle, causing a compensative response of the cardiac muscle, which progressively will lead to dilation and heart failure. At a cellular level, this corresponds to a considerable increase in the size of cardiomyocytes, known as cardiomyocyte hypertrophy, while their proliferation capacity is attenuated upon the first developmental stages. Cardiomyocytes, in order to cope with the increased workload (overload), suffer alterations in their morphology, nuclear content, energy metabolism, intracellular homeostatic mechanisms, contractile activity, and cell death mechanisms. Moreover, modifications in the cardiomyocyte niche, involving inflammation, immune infiltration, fibrosis, and angiogenesis, contribute to the subsequent events of a pathologic hypertrophic response. Considering the emerging need for a better understanding of the condition and treatment improvement, as the only available treatment option of AS consists of surgical interventions at a late stage of the disease, when the cardiac muscle state is irreversible, large animal models have been developed to mimic the human condition, to the greatest extend. Smaller animal models lack physiological, cellular and molecular mechanisms that sufficiently resemblance humans and in vitro techniques yet fail to provide adequate complexity. Animals, such as the ferret (Mustello purtorius furo), lapine (rabbit, Oryctolagus cunigulus), feline (cat, Felis catus), canine (dog, Canis lupus familiaris), ovine (sheep, Ovis aries), and porcine (pig, Sus scrofa), have contributed to research by elucidating implicated cellular and molecular mechanisms of the condition. Essential discoveries of each model are reported and discussed briefly in this review. Results of large animal experimentation could further be interpreted aiming at prevention of the disease progress or, alternatively, at regression of the implicated pathologic mechanisms to a physiologic state. This review summarizes the important aspects of the pathophysiology of LV hypertrophy and the applied surgical large animal models that currently better mimic the condition.

RhoA: a dubious molecule in cardiac pathophysiology

The Ras homolog gene family member A (RhoA) is the founding member of Rho GTPase superfamily originally studied in cancer cells where it was found to stimulate cell cycle progression and migration. RhoA acts as a master switch control of actin dynamics essential for maintaining cytoarchitecture of a cell. In the last two decades, however, RhoA has been coined and increasingly investigated as an essential molecule involved in signal transduction and regulation of gene transcription thereby affecting physiological functions such as cell division, survival, proliferation and migration. RhoA has been shown to play an important role in cardiac remodeling and cardiomyopathies; underlying mechanisms are however still poorly understood since the results derived from in vitro and in vivo experiments are still inconclusive. Interestingly its role in the development of cardiomyopathies or heart failure remains largely unclear due to anomalies in the current data available that indicate both cardioprotective and deleterious effects. In this review, we aimed to outline the molecular mechanisms of RhoA activation, to give an overview of its regulators, and the probable mechanisms of signal transduction leading to RhoA activation and induction of downstream effector pathways and corresponding cellular responses in cardiac (patho)physiology. Furthermore, we discuss the existing studies assessing the presented results and shedding light on the often-ambiguous data. Overall, we provide an update of the molecular, physiological and pathological functions of RhoA in the heart and its potential in cardiac therapeutics.

The copeptin response after physical activity is not associated with cardiac biomarkers or asymptomatic coronary artery disease: The North Sea Race Endurance Exercise Study (NEEDED) 2013

BACKGROUND

Copeptin concentrations increase both during acute coronary syndrome and following physical exercise. The relationship between copeptin increase following physical exercise and coronary artery disease (CAD) is uncertain. The aim of this study was to 1) describe the copeptin response following strenuous physical exercise, and 2) investigate the determinants of exercise induced copeptin concentrations, particularly in relation to cardiac biomarkers and CAD.

METHODS

Serum samples were collected from 97 recreational cyclists 24h before, and immediately, 3 and 24h after a 91-km bike race. Three subjects were subsequently diagnosed with significant asymptomatic CAD. Delta copeptin concentrations were correlated to patient characteristics and to biomarker concentrations.

RESULTS

Participants were 42.8±9.6years, and 76.3% were male. Copeptin concentrations increased to maximal levels immediately after the race and were normalized in >90% after 3h. A total of 53% and 39% exceeded the 95th and 99th percentile of the assay (10 and 19pmol/L) respectively. In multivariate models, race time, serum sodium, creatinine and cortisol were significant predictors of copeptin levels. There was no correlation between changes in copeptin and changes in cardiac biomarkers (hs-cTnI, hs-cTnT and BNP). Copeptin concentrations were normal in the subjects with asymptomatic CAD.

CONCLUSIONS

The moderate, short-term, exercise induced copeptin increase observed in the present study was not related to hs-cTn or BNP levels. Copeptin was normal in three asymptomatic recreational athletes with significant CAD.