Cardiomyocyte-Specific Overexpression of Activated Yes-Associated Protein Modified-RNA Promotes Cardiomyocyte Proliferation and Myocardial Regeneration.

Background: The proliferative capacity of cardiomyocytes in adult mammalian hearts is far too low to replace the cells that are lost to myocardial infarction. Both cardiomyocyte proliferation and myocardial regeneration can be improved via the overexpression of a constitutively active variant of YAP5SA (Yes-associated protein, 5SA [active] mutant), but persistent overexpression of proliferation-inducing genes could lead to hypertrophy and arrhythmia, whereas off-target expression in fibroblasts and macrophages could increase fibrosis and inflammation.

Methods And Results: Transient overexpression of YAP5SA or GFP (green fluorescent protein; control) was targeted to cardiomyocytes via our cardiomyocyte-specific modified mRNA translation system (CM-SMRTs or CM-SMRTs, respectively).

Identification of FDA-approved drugs that induce heart regeneration in mammals.

Targeting Meis1 and Hoxb13 transcriptional activity could be a viable therapeutic strategy for heart regeneration. In this study, we performd an in silico screening to identify FDA-approved drugs that can inhibit Meis1 and Hoxb13 transcriptional activity based on the resolved crystal structure of Meis1 and Hoxb13 bound to DNA. Paromomycin (Paro) and neomycin (Neo) induced proliferation of neonatal rat ventricular myocytes in vitro and displayed dose-dependent inhibition of Meis1 and Hoxb13 transcriptional activity by luciferase assay and disruption of DNA binding by electromobility shift assay.

Hypoxia-induced stabilization of HIF2A promotes cardiomyocyte proliferation by attenuating DNA damage.

Introduction: Gradual exposure to a chronic hypoxic environment leads to cardiomyocyte proliferation and improved cardiac function in mouse models through a reduction in oxidative DNA damage. However, the upstream transcriptional events that link chronic hypoxia to DNA damage have remained obscure.

Aim: We sought to determine whether hypoxia signaling mediated by the hypoxia-inducible factor 1 or 2 (HIF1A or HIF2A) underlies the proliferation phenotype that is induced by chronic hypoxia.

Analysis of cardiac single-cell RNA-sequencing data can be improved by the use of artificial-intelligence-based tools.

Single-cell RNA sequencing (scRNAseq) enables researchers to identify and characterize populations and subpopulations of different cell types in hearts recovering from myocardial infarction (MI) by characterizing the transcriptomes in thousands of individual cells. However, the effectiveness of the currently available tools for processing and interpreting these immense datasets is limited. We incorporated three Artificial Intelligence (AI) techniques into a toolkit for evaluating scRNAseq data: AI Autoencoding separates data from different cell types and subpopulations of cell types (cluster analysis); AI Sparse Modeling identifies genes and signaling mechanisms that are differentially activated between subpopulations (pathway/gene set enrichment analysis), and AI Semisupervised Learning tracks the transformation of cells from one subpopulation into another (trajectory analysis).

A three-dimensional culture system for generating cardiac spheroids composed of cardiomyocytes, endothelial cells, smooth-muscle cells, and cardiac fibroblasts derived from human induced-pluripotent stem cells.

Cardiomyocytes (CMs), endothelial cells (ECs), smooth-muscle cells (SMCs), and cardiac fibroblasts (CFs) differentiated from human induced-pluripotent stem cells (hiPSCs) are the fundamental components of cell-based regenerative myocardial therapy and can be used as models for mechanistic studies and drug testing. However, newly differentiated hiPSC-CMs tend to more closely resemble fetal CMs than the mature CMs of adult hearts, and current techniques for improving CM maturation can be both complex and labor-intensive. Thus, the production of CMs for commercial and industrial applications will require more elementary methods for promoting CM maturity.

Cardiomyocyte Cell-Cycle Regulation in Neonatal Large Mammals: Single Nucleus RNA-Sequencing Data Analysis an Artificial-Intelligence-Based Pipeline.

Adult mammalian cardiomyocytes have very limited capacity to proliferate and repair the myocardial infarction. However, when apical resection (AR) was performed in pig hearts on postnatal day (P) 1 (AR) and acute myocardial infarction (MI) was induced on P28 (MI), the animals recovered with no evidence of myocardial scarring or decline in contractile performance. Furthermore, the repair process appeared to be driven by cardiomyocyte proliferation, but the regulatory molecules that govern the AR-induced enhancement of myocardial recovery remain unclear.

Retronasal Aroma of Beef Pate Analyzed by a Chewing Simulator.

In retronasal aroma, the targeted aroma compounds are released from food during chewing. The changes in the food structures during chewing strongly influence the release of the compounds, therefore affecting the perception of food. Here, the relationship between retronasal aroma and food deliciousness based on the physicochemical properties of aroma compounds was examined.

TT-10-loaded nanoparticles promote cardiomyocyte proliferation and cardiac repair in a mouse model of myocardial infarction.

The meager regenerative capacity of adult mammalian hearts appears to be driven by the proliferation of endogenous cardiomyocytes; thus, strategies targeting mechanisms of cardiomyocyte cell cycle regulation, such as the Hippo/Yes-associated protein (Hippo/Yap) pathway, could lead to the development of promising therapies for heart disease. The pharmacological product TT-10 increases cardiomyocyte proliferation by upregulating nuclear Yap levels. When intraperitoneal injections of TT-10 were administered to infarcted mouse hearts, the treatment promoted cardiomyocyte proliferation and was associated with declines in infarct size 1 week after administration, but cardiac function worsened at later time points.

Cyclin D2 Overexpression Enhances the Efficacy of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Myocardial Repair in a Swine Model of Myocardial Infarction.

Background: Human induced pluripotent stem cells with normal (wild-type) or upregulated (overexpressed) levels of CCND2 (cyclin D2) expression were differentiated into cardiomyocytes (CCND2CMs or CCND2CMs, respectively) and injected into infarcted pig hearts.

Methods: Acute myocardial infarction was induced by a 60-minute occlusion of the left anterior descending coronary artery. Immediately after reperfusion, CCND2CMs or CCND2CMs (3×10 cells each) or an equivalent volume of the delivery vehicle was injected around the infarct border zone area.

Identification of tetracycline combinations as EphB1 tyrosine kinase inhibitors for treatment of neuropathic pain.

Previous studies have demonstrated that the synaptic EphB1 receptor tyrosine kinase is a major mediator of neuropathic pain, suggesting that targeting the activity of this receptor might be a viable therapeutic option. Therefore, we set out to determine if any FDA-approved drugs can act as inhibitors of the EphB1 intracellular catalytic domain. An in silico screen was first used to identify a number of tetracycline antibiotics which demonstrated potential docking to the ATP-binding catalytic domain of EphB1.

Changes in Cardiomyocyte Cell Cycle and Hypertrophic Growth During Fetal to Adult in Mammals.

The failure of adult cardiomyocytes to reproduce themselves to repair an injury results in the development of severe cardiac disability leading to death in many cases. The quest for an understanding of the inability of cardiac myocytes to repair an injury has been ongoing for decades with the identification of various factors which have a temporary effect on cell-cycle activity. Fetal cardiac myocytes are continuously replicating until the time that the developing fetus reaches a stage of maturity sufficient for postnatal life around the time of birth.

Experimental Hypoxia as a Model for Cardiac Regeneration in Mice.

Experimental hypoxia has been used for decades to examine the adaptive response to low-oxygen environments. Various models have been studied, including flies, worms, fish, rodents, and humans. Our lab has recently used this technology to examine the effect of environmental hypoxia on mammalian heart regeneration.

A calcineurin-Hoxb13 axis regulates growth mode of mammalian cardiomyocytes.

A major factor in the progression to heart failure in humans is the inability of the adult heart to repair itself after injury. We recently demonstrated that the early postnatal mammalian heart is capable of regeneration following injury through proliferation of preexisting cardiomyocytes and that Meis1, a three amino acid loop extension (TALE) family homeodomain transcription factor, translocates to cardiomyocyte nuclei shortly after birth and mediates postnatal cell cycle arrest. Here we report that Hoxb13 acts as a cofactor of Meis1 in postnatal cardiomyocytes.

Mechanism of Eccentric Cardiomyocyte Hypertrophy Secondary to Severe Mitral Regurgitation.

Background: Primary valvular heart disease is a prevalent cause of morbidity and mortality in both industrialized and developing countries. Although the primary consequence of valvular heart disease is myocardial dysfunction, treatment of valvular heart diseases centers around valve repair or replacement rather than prevention or reversal of myocardial dysfunction. This is particularly evident in primary mitral regurgitation (MR), which invariably results in eccentric hypertrophy and left ventricular (LV) failure in the absence of timely valve repair or replacement.

Hypoxia promotes primitive glycosaminoglycan-rich extracellular matrix composition in developing heart valves.

During postnatal heart valve development, glycosaminoglycan (GAG)-rich valve primordia transform into stratified valve leaflets composed of GAGs, fibrillar collagen, and elastin layers accompanied by decreased cell proliferation as well as thinning and elongation. The neonatal period is characterized by the transition from a uterine environment to atmospheric O, but the role of changing O levels in valve extracellular matrix (ECM) composition or morphogenesis is not well characterized. Here, we show that tissue hypoxia decreases in mouse aortic valves in the days after birth, concomitant with ECM remodeling and cell cycle arrest of valve interstitial cells.

Hypoxia-induced myocardial regeneration.

The underlying cause of systolic heart failure is the inability of the adult mammalian heart to regenerate damaged myocardium. In contrast, some vertebrate species and immature mammals are capable of full cardiac regeneration following multiple types of injury through cardiomyocyte proliferation. Little is known about what distinguishes proliferative cardiomyocytes from terminally differentiated, nonproliferative cardiomyocytes.

Hypoxia induces heart regeneration in adult mice.

The adult mammalian heart is incapable of regeneration following cardiomyocyte loss, which underpins the lasting and severe effects of cardiomyopathy. Recently, it has become clear that the mammalian heart is not a post-mitotic organ. For example, the neonatal heart is capable of regenerating lost myocardium, and the adult heart is capable of modest self-renewal.

Visualization and Lineage Tracing of Pax7 Spermatogonial Stem Cells in the Mouse.

The precise identity of spermatogonial stem cells-the germline stem cell of the adult testis-remains a controversial topic. Technical limitations have included the lack of specific markers and methods for lineage tracing of A spermatogonia and their subsets. Immunolocalization of proteins in tissue sections has been a standard tool for the in situ identification and visualization of rare cellular subsets.

Regulation of FOXO3 subcellular localization by Kit ligand in the neonatal mouse ovary.

Purpose: Foxo3 protein is required in the oocyte nucleus for the maintenance of primordial follicles in a dormant state. PI3K/AKT-dependent phosphorylation of Foxo3 leads to its relocalization to the cytoplasm and subsequent follicular activation. However, the nature of the upstream signals controlling Foxo3 activity and subcellular localization remains unknown.