Cardiomyocyte hyperplasia and immaturity but not hypertrophy are characteristic features of patients with RASopathies

Cardiovascular aspects of Noonan syndrome and related disorders

Noonan syndrome and other RASopathies constitute an important group of disorders to be considered in the differential diagnosis in individuals with congenital heart defects and hypertrophic cardiomyopathy. The cardiovascular phenotype of RASopathies is complex and comprises a spectrum of abnormalities, including not only congenital defects but also abnormalities affecting the lymphovascular system and other anomalies of the vascular system, which may emerge over the course of an individual's lifetime. Affected individuals typically present with a syndromic phenotype, exhibiting additional physical symptoms outside of the cardiovascular system and neuropsychological deficits. Genetic testing of the established disease genes for RASopathies is an effective method for identifying the underlying genetic variant in the majority of cases. This approach is strongly recommended to facilitate a more precise prognosis and the potential for personalized targeted therapies. Screening for RASopathy-associated gene variants in individuals with isolated CHDs, HCM, or other isolated cardiovascular features outside the NS spectrum appears to have limited clinical utility. However, it should be noted that the RASopathy phenotype may be challenging to discern in cases of mild or oligosymptomatic involvement, or it may be obscured by the presence of severe medical conditions, particularly in very young children.

Rostafuroxin, the inhibitor of endogenous ouabain, ameliorates chronic undernutrition-induced hypertension, stroke volume, cardiac output, left-ventricular fibrosis and alterations in Na+-transporting ATPases in rats

Our aim has been to investigate the effect of Rostafuroxin, an inhibitor of endogenous cardiotonic steroids (EO/CTS), on cardiac structure and function and cardiac Na+ transport in undernourished hypertensive Wistar rats, and to determine whether chronic undernutrition is a modifiable risk factor for cardiovascular-kidney-metabolic (CKM) syndrome. Echocardiographic studies evaluated stroke volume cardiac output, ejection fraction, mitral valve early diastolic blood flow/late diastolic blood flow (E/A) ratio, and right renal resistive index. The cardiomyocyte area and collagen infiltration of cardiac tissue were investigated, as also the activities of the cardiac ouabain-sensitive (Na++K+)ATPase ((Na++K+)ATPase Sens) and ouabain-resistant Na+-ATPase (Na+-ATPase Res). Undernourished hypertensive rats presented tachycardia, reduced stroke volume, decreased cardiac output, preserved fractional shortening and ejection fraction, unmodified mitral valve E/A ratio, and increased right renal resistive index. Cardiomyocyte size decreased and intense collagen infiltration had occurred. The (Na++K+)ATPase Sens activity decreased, whereas that of Na+-ATPase Res increased. Rostafuroxin selectively modified some of these echocardiographic and molecular parameters: it increased stroke volume and cardiac output and prevented histopathological alterations. The drug decreased and increased the activities of (Na++K+)ATPase Sens and Na+-ATPase Res, respectively, in normonourished rats, and the opposite trend was found in the undernourished group. It is concluded that chronic undernutrition in rats can provoke structural, functional, histological, and molecular cardiovascular alterations that, with the simultaneous changes in renal parameters described in this and in previous studies, configure an undescribed type of CKM syndrome. The data also demonstrate that the blockade of EO/CTS ameliorates stroke volume and cardiac output, thus preventing or delaying the worsening of the syndrome.

Biomarker Landscape in RASopathies

RASopathies are a group of related genetic disorders caused by mutations in genes within the RAS/MAPK signaling pathway. This pathway is crucial for cell division, growth, and differentiation, and its disruption can lead to a variety of developmental and health issues. RASopathies present diverse clinical features and pose significant diagnostic and therapeutic challenges. Studying the landscape of biomarkers in RASopathies has the potential to improve both clinical practices and the understanding of these disorders. This review provides an overview of recent discoveries in RASopathy molecular profiling, which extend beyond traditional gene mutation analysis. mRNAs, non-coding RNAs, protein expression patterns, and post-translational modifications characteristic of RASopathy patients within pivotal signaling pathways such as the RAS/MAPK, PI3K/AKT/mTOR, and Rho/ROCK/LIMK2/cofilin pathways are summarized. Additionally, the field of metabolomics holds potential for uncovering metabolic signatures associated with specific RASopathies, which are crucial for developing precision medicine. Beyond molecular markers, we also examine the role of histological characteristics and non-invasive physiological assessments in identifying potential biomarkers, as they provide evidence of the disease's effects on various systems. Here, we synthesize key findings and illuminate promising avenues for future research in RASopathy biomarker discovery, underscoring rigorous validation and clinical translation.

Time-dependent effects of BRAF-V600E on cell cycling, metabolism, and function in engineered myocardium

Candidate cardiomyocyte (CM) mitogens such as those affecting the extracellular signal-regulated kinase (ERK) signaling pathway represent potential targets for functional heart regeneration. We explored whether activating ERK via a constitutively active mutant of B-raf proto-oncogene (BRAF), BRAF-V600E (caBRAF), can induce proproliferative effects in neonatal rat engineered cardiac tissues (ECTs). Sustained CM-specific caBRAF expression induced chronic ERK activation, substantial tissue growth, deficit in sarcomeres and contractile function, and tissue stiffening, all of which persisted for at least 4 weeks of culture. caBRAF-expressing CMs in ECTs exhibited broad transcriptomic changes, shift to glycolytic metabolism, loss of connexin-43, and a promigratory phenotype. Transient, doxycycline-controlled caBRAF expression revealed that the induction of CM cycling is rapid and precedes functional decline, and the effects are reversible only with short-lived ERK activation. Together, direct activation of the BRAF kinase is sufficient to modulate CM cycling and functional phenotype, offering mechanistic insights into roles of ERK signaling in the context of cardiac development and regeneration.