Evaluation of Senescence and Its Prevention in Doxorubicin-Induced Cardiotoxicity Using Dynamic Engineered Heart Tissues.

Background: Doxorubicin is an essential cancer treatment, but its usefulness is hampered by the occurrence of cardiotoxicity. Nevertheless, the pathophysiology underlying doxorubicin-induced cardiotoxicity and the respective molecular mechanisms are poorly understood. Recent studies have suggested involvement of cellular senescence. Objectives: The aims of this study were to establish whether senescence is present in patients with doxorubicin-induced cardiotoxicity and to investigate if this could be used as a potential treatment target. Methods: Biopsies from the left ventricles of patients with severe doxorubicin-induced cardiotoxicity were compared with control samples. Additionally, senescence-associated mechanisms were characterized in 3-dimensional dynamic engineered heart tissues (dyn-EHTs) and human pluripotent stem cell-derived cardiomyocytes. These were exposed to multiple, clinically relevant doses of doxorubicin to recapitulate patient treatment regimens. To prevent senescence, dyn-EHTs were cotreated with the senomorphic drugs 5-aminoimidazole-4-carboxamide ribonucleotide and resveratrol. Results: Senescence-related markers were significantly up-regulated in the left ventricles of patients with doxorubicin-induced cardiotoxicity. Treatment of dyn-EHTs resulted in up-regulation of similar senescence markers as seen in the patients, accompanied by tissue dilatation, decreased force generation, and increased troponin release. Treatment with senomorphic drugs led to decreased expression of senescence-associated markers, but this was not accompanied by improved function. Conclusions: Senescence was observed in the hearts of patients with severe doxorubicin-induced cardiotoxicity, and this phenotype can be modeled in vitro by exposing dyn-EHTs to repeated clinically relevant doses of doxorubicin. The senomorphic drugs 5-aminoimidazole-4-carboxamide ribonucleotide and resveratrol prevent senescence but do not result in functional improvements. These findings suggest that preventing senescence by using a senomorphic during doxorubicin administration might not prevent cardiotoxicity.

Review: Precision Medicine Approaches for Genetic Cardiomyopathy: Targeting Phospholamban R14del.

PURPOSE OF REVIEW: Heart failure is a syndrome with poor prognosis and no curative options for the majority of patients. The standard one-size-fits-all-treatment approach, targeting neurohormonal dysregulations, helps to modulate symptoms of heart failure, but fails to address the cause of the problem. Precision medicine aims to go beyond symptom modulation and targets pathophysiological mechanisms that underlie disease. In this review, an overview of how precision medicine can be approached as a treatment strategy for genetic heart disease will be discussed. PLN R14del, a genetic mutation known to cause cardiomyopathy, will be used as an example to describe the potential and pitfalls of precision medicine. RECENT FINDINGS: PLN R14del is characterized by several disease hallmarks including calcium dysregulation, metabolic dysfunction, and protein aggregation. The identification of disease-related biological pathways and the effective targeting using several modalities, including gene silencing and signal transduction modulation, may eventually provide novel treatments for genetic heart disease. We propose a workflow on how to approach precision medicine in heart disease. This workflow focuses on deep phenotyping of patient derived material, including in vitro disease modeling. This will allow identification of therapeutic targets and disease modifiers, to be used for the identification of novel biomarkers and the development of precision medicine approaches for genetic cardiomyopathies.

Selenoprotein DIO2 Is a Regulator of Mitochondrial Function, Morphology and UPRmt in Human Cardiomyocytes.

Members of the fetal-gene-program may act as regulatory components to impede deleterious events occurring with cardiac remodeling, and constitute potential novel therapeutic heart failure (HF) targets. Mitochondrial energy derangements occur both during early fetal development and in patients with HF. Here we aim to elucidate the role of DIO2, a member of the fetal-gene-program, in pluripotent stem cell (PSC)-derived human cardiomyocytes and on mitochondrial dynamics and energetics, specifically. RNA sequencing and pathway enrichment analysis was performed on mouse cardiac tissue at different time points during development, adult age, and ischemia-induced HF. To determine the function of DIO2 in cardiomyocytes, a stable human hPSC-line with a DIO2 knockdown was made using a short harpin sequence. Firstly, we showed the selenoprotein, type II deiodinase (DIO2): the enzyme responsible for the tissue-specific conversion of inactive (T4) into active thyroid hormone (T3), to be a member of the fetal-gene-program. Secondly, silencing DIO2 resulted in an increased reactive oxygen species, impaired activation of the mitochondrial unfolded protein response, severely impaired mitochondrial respiration and reduced cellular viability. Microscopical 3D reconstruction of the mitochondrial network displayed substantial mitochondrial fragmentation. Summarizing, we identified DIO2 to be a member of the fetal-gene-program and as a key regulator of mitochondrial performance in human cardiomyocytes. Our results suggest a key position of human DIO2 as a regulator of mitochondrial function in human cardiomyocytes.