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Aims: RASopathies are caused by mutations in genes that alter the MAP kinase pathway and are marked by several malformations with cardiovascular disorders as the predominant cause of mortality. Mechanistic insights in the underlying pathogenesis in affected cardiac tissue are rare. The aim of the study was to assess the impact of RASopathy causing mutations on the human heart., Methods and Results: Using single cell approaches and histopathology we analyzed cardiac tissue from children with different RASopathy-associated mutations compared to age-matched dilated cardiomyopathy (DCM) and control hearts. The volume of cardiomyocytes was reduced in RASopathy conditions compared to controls and DCM patients, and the estimated number of cardiomyocytes per heart was ∼4-10 times higher. Single nuclei RNA sequencing of a 13-year-old RASopathy patient (carrying a PTPN11 c.1528C > G mutation) revealed that myocardial cell composition and transcriptional patterns were similar to <1 year old DCM hearts. Additionally, immaturity of cardiomyocytes is shown by an increased MYH6/MYH7 expression ratio and reduced expression of genes associated with fatty acid metabolism. In the patient with the PTPN11 mutation activation of the MAP kinase pathway was not evident in cardiomyocytes, whereas increased phosphorylation of PDK1 and its downstream kinase Akt was detected., Conclusion: In conclusion, an immature cardiomyocyte differentiation status appears to be preserved in juvenile RASopathy patients. The increased mass of the heart in such patients is due to an increase in cardiomyocyte number (hyperplasia) but not an enlargement of individual cardiomyocytes (hypertrophy)., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Dilated cardiomyopathy (DCM) is a leading cause of death in children with heart failure. The outcome of pediatric heart failure treatment is inconsistent, and large cohort studies are lacking. Progress may be achieved through personalized therapy that takes age- and disease-related pathophysiology, pathology, and molecular fingerprints into account. We present single nuclei RNA sequencing from pediatric patients with DCM as the next step in identifying cellular signatures., Methods: We performed single nuclei RNA sequencing with heart tissues from 6 children with DCM with an age of 0.5, 0.75, 5, 6, 12, and 13 years. Unsupervised clustering of 18 211 nuclei led to the identification of 14 distinct clusters with 6 major cell types., Results: The number of nuclei in fibroblast clusters increased with age in patients with DCM, a finding that was confirmed by histological analysis and was consistent with an age-related increase in cardiac fibrosis quantified by cardiac magnetic resonance imaging. Fibroblasts of patients with DCM >6 years of age showed a profoundly altered gene expression pattern with enrichment of genes encoding fibrillary collagens, modulation of proteoglycans, switch in thrombospondin isoforms, and signatures of fibroblast activation. In addition, a population of cardiomyocytes with a high proregenerative profile was identified in infant patients with DCM but was absent in children >6 years of age. This cluster showed high expression of cell cycle activators such as cyclin D family members, increased glycolytic metabolism and antioxidative genes, and alterations in ß-adrenergic signaling genes., Conclusions: Novel insights into the cellular transcriptomes of hearts from pediatric patients with DCM provide remarkable age-dependent changes in the expression patterns of fibroblast and cardiomyocyte genes with less fibrotic but enriched proregenerative signatures in infants.

While in adults major advances in heart failure therapy in patients with dilated cardiomyopathy were documented in the last two decades, research on the mechanism and therapies of heart failure in children with left ventricular dilated cardiomyopathy has lagged behind. Despite the lack of sufficient randomized prospective studies, ACE inhibitors are first line and ß-receptor antagonists are second-line strategies in children. Following the adult guidelines, without having data concerning the pediatric population, mineral corticoids are also accepted in the treatment of pediatric heart failure, while diuretics should only be used to achieve a euvolemic status. In cases of complete left bundle bunch block or prolonged QRS duration, cardiac resynchronization is an option. If these instruments are exploited, and the child is still listed for heart transplantation as destination, evolving therapies like pulmonary artery banding in cases of preserved right ventricular function and cardiac cell therapy in cases of localized ventricular dysfunction might represent additional treatment options. This review summarizes the actual guidelines and provides an outlook for evolving therapies.

Objective: Dilated cardiomyopathy is a leading cause of cardiac death in children. Approximately 30% of children die or need cardiac transplantation in the first year after establishing the diagnosis. New strategies are needed to improve the outcome in this high-risk patient population., Method and Results: We present our experience in 38 patients below the age of three years, who were diagnosed with dilated cardiomyopathy and who were treated at our institution between 2006 and 2012. The treatment strategy involved institution of β-blockers and angiotensin-converting enzyme inhibitors as soon as feasible. In selected cases, pulmonary artery banding or intracoronary autologous bone marrow-derived cell therapy was performed. The median age at presentation was six months (range 1-26 months). The median follow-up age was 16 months (range 2-80 months). Kaplan-Meier analysis of survival after dilated cardiomyopathy diagnosis revealed a one-year survival of 97% and a five-year survival of 86%. The rate of freedom from death or heart transplantation was 82% at one year and 69% at five years. Surviving patients who were free of transplantation, at the follow-up at 25 months (3-80 months), showed a significant improvement in left ventricular ejection fraction (from 19±11 to 46±16%) and left ventricular end-diastolic diameter (z-score from 4.6±2.4 to 1.4±1.6). In addition, the levels of B-type natriuretic peptide improved significantly (from 3330±3840 to 171±825 pg/ml)., Conclusion: Our data suggest that the clinical approach described here may result in a markedly improved medium-term outcome in young children with dilated cardiomyopathy. Further studies are required to evaluate whether these approaches reduce end-points such as transplantation or death.

Background: Dilated cardiomyopathy (DCM) in childhood has a considerable morbidity and mortality and high incidence of heart transplantation. Pulmonary artery banding (PAB) has been proposed in patients with corrected transposition of the great arteries to retrain the sub-pulmonic left ventricle (LV) and to improve a failing sub-aortic right ventricle. We evaluated the short-term and medium-term effects of PAB in young patients with LVDCM., Methods: A retrospective single-center observational study was performed to evaluate the possible benefits of a dilatable surgical PAB in infants and young children with LVDCM., Results: Reported are 12 patients (10 infants, 2 toddlers) with LVDCM referred for heart transplant who received a surgical PAB. There were no hospital deaths. Clinical functional status improved in all patients. The pressure gradient across the PAB increased within 20 days from 28 ± 7 to 43 ± 15 mm Hg. The LV ejection fraction increased from 14.5% ± 5% pre-PAB to 27% ± 13% at hospital discharge and to 47% ± 10% at 3 to 6 months. The LV end-diastolic diameter (z-score) decreased (p > 0.001) from 46 ± 6.1 (+7.0 ± 1.3) to 35 ± 15 mm (+3.0 ± 1.3) after 3 to 6 months and to 34 ± 15 mm (+1.3 ± 1.14) after a median age of 2 years (maximum 6.6 years), respectively. Plasma B-type natriuretic peptide levels decreased from 3431 ± 2610 to 288 ± 321 pg/ml at discharge and to 102 ± 96 pg/ml 22 months later. Eight children were subsequently de-banded by transcatheter technique and 6 of them are currently at Ross Heart Failure Classification for Children class I. Two patients, both with non-compaction DCM, deteriorated at 5 and 6 months after PAB debanding and finally died., Conclusion: In young children with LVDCM and still-preserved right ventricular function, PAB led to an improvement of LV and mitral valve function by ventricular interaction., (Copyright © 2013 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.)

DCM is the most common cardiomyopathy in childhood. Effectiveness of anticongestive therapy is limited in most cases and about one-third of children diagnosed with DCM die or receive heart transplantation within the first year after diagnosis. Cardiac stem cell transplantation has become a promising therapy to treat heart failure in adult patients. Based on these promising results, the cardiac stem cell therapy might also represent a new therapeutic option particularly in young children. The present case documents for the first time intracoronary administration of autologous bone marrow-derived progenitor cells in a critically ill two-yr-old child with severe heart failure caused by DCM. Because of progressive worsening of the clinical condition despite maximal anticongestive treatment, the decision to perform autologous stem cell therapy was made. Cardiac stem cell therapy proved to be technically feasible, was associated with improvement in cardiac function, and might represent an option before heart transplantation in children with severe heart failure.