Fetal Hypoxia Impacts on Proliferation and Differentiation of Sca-1+ Cardiac Progenitor Cells and Maturation of Cardiomyocytes: A Role of MicroRNA-210

Whole-Exome Sequencing Identifies Homozygote Nonsense Variants in LMOD2 Gene Causing Infantile Dilated Cardiomyopathy

As an essential component of the sarcomere, actin thin filament stems from the Z-disk extend toward the middle of the sarcomere and overlaps with myosin thick filaments. Elongation of the cardiac thin filament is essential for normal sarcomere maturation and heart function. This process is regulated by the actin-binding proteins Leiomodins (LMODs), among which LMOD2 has recently been identified as a key regulator of thin filament elongation to reach a mature length. Few reports have implicated homozygous loss of function variants of LMOD2 in neonatal dilated cardiomyopathy (DCM) associated with thin filament shortening. We present the fifth case of DCM due to biallelic variants in the LMOD2 gene and the second case with the c.1193G>A (p.W398*) nonsense variant identified by whole-exome sequencing. The proband is a 4-month male infant of Hispanic descent with advanced heart failure. Consistent with previous reports, a myocardial biopsy exhibited remarkably short thin filaments. However, compared to other cases of identical or similar biallelic variants, the patient presented here has an unusually late onset of cardiomyopathy during infancy. Herein, we present the phenotypic and histological features of this variant, confirm the pathogenic impact on protein expression and sarcomere structure, and discuss the current knowledge of LMOD2-related cardiomyopathy.

Epigenetic Modification Factors and microRNAs Network Associated with Differentiation of Embryonic Stem Cells and Induced Pluripotent Stem Cells toward Cardiomyocytes: A Review

More research is being conducted on myocardial cell treatments utilizing stem cell lines that can develop into cardiomyocytes. All of the forms of cardiac illnesses have shown to be quite amenable to treatments using embryonic (ESCs) and induced pluripotent stem cells (iPSCs). In the present study, we reviewed the differentiation of these cell types into cardiomyocytes from an epigenetic standpoint. We also provided a miRNA network that is devoted to the epigenetic commitment of stem cells toward cardiomyocyte cells and related diseases, such as congenital heart defects, comprehensively. Histone acetylation, methylation, DNA alterations, N6-methyladenosine (m⁶a) RNA methylation, and cardiac mitochondrial mutations are explored as potential tools for precise stem cell differentiation.

High cardiomyocyte diversity in human early prenatal heart development

Cardiomyocytes play key roles during cardiogenesis, but have poorly understood features, especially in prenatal stages. Here, we characterized human prenatal cardiomyocytes, 6.5-7 weeks post-conception, by integrating single-cell RNA sequencing, spatial transcriptomics, and ligand-receptor interaction information. Using a computational workflow developed to dissect cell type heterogeneity, localize cell types, and explore their molecular interactions, we identified eight types of developing cardiomyocyte, more than double compared to the ones identified in the Human Developmental Cell Atlas. These have high variability in cell cycle activity, mitochondrial content, and connexin gene expression, and are differentially distributed in the ventricles, including outflow tract, and atria, including sinoatrial node. Moreover, cardiomyocyte ligand-receptor crosstalk is mainly with non-cardiomyocyte cell types, encompassing cardiogenesis-related pathways. Thus, early prenatal human cardiomyocytes are highly heterogeneous and develop unique location-dependent properties, with complex ligand-receptor crosstalk. Further elucidation of their developmental dynamics may give rise to new therapies.

Recent insights into the microRNA and long non-coding RNA-mediated regulation of stem cell populations

Stem cells are undifferentiated cells that have multi-lineage differentiation. The transition from self-renewal to differentiation requires rapid and extensive gene expression alterations. Since different stem cells exhibit diverse non-coding RNAs (ncRNAs) expression profiles, the critical roles of ncRNAs in stem cell reprogramming, pluripotency maintenance, and differentiation have been widely investigated over the past few years. Hence, in this current review, the two main categories of ncRNAs, microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are discussed. While the primary way by which miRNAs restrict mRNA transcription is through miRNA-mRNA interaction, lncRNAs have a wide range of effects on mRNA functioning, including interactions with miRNAs. Both of these ncRNAs participate in the post-transcriptional regulation of crucial biological mechanisms, such as cell cycle regulation, apoptosis, aging, and cell fate decisions. These findings shed light on a previously unknown aspect of gene regulation in stem cell fate determination and behavior. Overall, we summarized the key roles of miRNAs (including exosomal miRNAs) and lncRNAs in the regulation of stem cell populations, such as cardiac, hematopoietic, mesenchymal, neural, and spermatogonial, as well ncRNAs' influence on malignancy through modulating cancer stem cells, which might significantly contribute to clinical stem cell therapy and in regenerative medicine.

Circulating microRNA: Myocardium-derived prenatal biomarker of ventricular septal defects

Background: Recently, circulating microRNAs (miRNAs) from maternal blood and amniotic fluid have been used as biomarkers for ventricular septal defect (VSD) diagnosis. However, whether circulating miRNAs are associated with fetal myocardium remains unknown.

Methods: Dimethadione (DMO) induced a VSD rat model. The miRNA expression profiles of the myocardium, amniotic fluid and maternal serum were analyzed. Differentially expressed microRNAs (DE-microRNAs) were verified by qRT–PCR. The target gene of miR-1-3p was confirmed by dual luciferase reporter assays. Expression of amniotic fluid-derived DE-microRNAs was verified in clinical samples.

Results: MiRNAs were differentially expressed in VSD fetal rats and might be involved in cardiomyocyte differentiation and apoptosis. MiR-1-3p, miR-1b and miR-293-5p were downregulated in the myocardium and upregulated in amniotic fluid/maternal serum. The expression of amniotic fluid-derived DE-microRNAs (miR-1-3p, miR-206 and miR-184) was verified in clinical samples. Dual luciferase reporter assays confirmed that miR-1-3p directly targeted SLC8A1/NCX1.

Conclusion: MiR-1-3p, miR-1b and miR-293-5p are downregulated in VSD myocardium and upregulated in circulation and may be released into circulation by cardiomyocytes. MiR-1-3p targets SLC8A1/NCX1 and participates in myocardial apoptosis. MiR-1-3p upregulation in circulation is a direct and powerful indicator of fetal VSD and is expected to serve as a prenatal VSD diagnostic marker.

Epigenetics in Congenital Heart Disease

Embryonic heart development is an intricate process that mainly involves morphogens, transcription factors, and cardiac genes. The precise spatiotemporal expression of these genes during different developmental stages underlies normal heart development. Thus, mutation or aberrant expression of these genes may lead to congenital heart disease (CHD). However, evidence demonstrates that the mutation of genes accounts for only a small portion of CHD cases, whereas the aberrant expression regulated by epigenetic modification plays a predominant role in the pathogenesis of CHD. In this review, we provide essential knowledge on the aberrant epigenetic modification involved in the pathogenesis of CHD. Then, we discuss recent advances in the identification of novel epigenetic biomarkers. Last, we highlight the epigenetic roles in some adverse intrauterine environment‐related CHD, which may help the prevention, diagnosis, and treatment of these kinds of CHD.

Characterization of early myocardial inflammation in ischemia-reperfusion injury

Background

Myocardial injury may be caused by myocardial ischemia-reperfusion (IR), and salvaging such an injury is still a great challenge in clinical practice. This study comprehensively characterized the physiopathologic changes of myocardial injury after IR to explore the underlying mechanism in the early reperfusion phase with particular emphasis on early myocardial inflammation.

Methods and Results

The experimental IR model was obtained by the left anterior descending artery's transient ligation of C57BL/6 mice. T2W signals of all mice showed increased signal at different IR stages. It was positively correlated with inflammatory cytokines and cells. T2W imaging by 7.0 T MRI surprisingly detected signal enhancement, but histopathology and flow cytometry did not reveal any inflammatory cells infiltration within 3 h after IR. Cardiomyocyte swelling and increased vascular permeability were observed by WGA staining and ultrastructural analysis, respectively. The 3 h IR group showed that the cardiomyocytes were severely affected with disintegrating myofilaments and mitochondria. Both VEGF and phosphorylated Src protein were markedly expressed in the 3 h IR group in comparison with the sham group, and TUNEL staining displayed little positive cells. Cleaved caspase-3 apoptin also has similar expression levels with that of the sham group. Resident macrophages had notably become M1 phenotype. The T2W signal was still elevated, and we observed that collagen deposition occurred from 1 to 7 days.

Conclusions

The inflammation response during the first week after reperfusion injury gradually increase 3 h later, but the main manifestation before that was edema. This study indicated that the first 3 h may be crucial to the early rescue process for reperfusion-induced myocardial injury due to inflammatory cell infiltration absence and apoptosis.

Antenatal Hypoxia Accelerates the Onset of Alzheimer's Disease Pathology in 5xFAD Mouse Model

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder associated with cognitive impairment and later dementia among the elderly. Mounting evidence shows that adverse maternal environments during the fetal development increase the risk of diseases later in life including neurological disorders, and suggests an early origin in the development of AD-related dementia (ADRD) in utero. In the present study, we investigated the impact of antenatal hypoxia and fetal stress on the initiation of AD-related pathology in offspring of 5xFAD mice. We showed that fetal hypoxia significantly reduced brain and body weight in the fetal and the early postnatal period, which recovered in young adult mice. Using spontaneous Y-maze, novel object recognition (NOR), and open field (OF) tasks, we found that antenatal hypoxia exacerbated cognitive decline in offspring of 5xFAD compared with normoxia control. Of interest, fetal hypoxia did not alter intraneuronal soluble amyloid-β (Aβ) oligomer accumulation in the cortex and hippocampus in 5xFAD mouse offspring, indicating that antenatal hypoxia increased the vulnerability of the brain to synaptotoxic Aβ in the disease onset later in life. Consistent with the early occurrence of cognitive decline, we found synapse loss but not neuronal death in the cerebral cortex in 5xFAD but not wild-type (WT) offspring exposed to antenatal hypoxia. Furthermore, we also demonstrated that antenatal hypoxia significantly increased microglial number and activation, and reactive astrogliosis in the cerebral cortex in WT offspring. Moreover, antenatal hypoxia resulted in an exacerbated increase of microgliosis and astrogliosis in the early stage of AD in 5xFAD offspring. Together, our study reveals a causative link between fetal stress and the accelerated onset of AD-related pathology, and provides mechanistic insights into the developmental origin of aging-related neurodegenerative disorders.