Microarray Analysis of Differential Gene Expression Profile Between Human Fetal and Adult Heart

Early-life exposure to lead changes cardiac development and compromises long-term cardiac function

Lead (Pb) is widely used in industrial and daily-use consumer products. Early-life exposure may increase the risk of lead-related heart problems in childhood. However, the effects of early-life lead exposure on fetal heart development and long-term cardiac outcomes are unknown. In this study, pregnant ICR mice were exposed to lead acetate trihydrate (50 mg/kg/d) via oral gavage from gestation day 1.5 until offspring weaning. Thereafter, the second hit model was established, two groups of offspring (4 weeks old) were either administered sterile saline or Angiotensin II (Ang II) for 4 weeks until euthanasia. We investigated lead-induced offspring heart damage from embryonic period to adulthood by echocardiographic analysis, pathological H&E staining, and ultrastructural examination, as well as mitochondrial function detection. The results showed early-life lead exposure predisposed offspring mice to decreased ejection fraction, increased left ventricular volume, accompanied by hypertrophy and dilation, cardiomyocyte sarcomere dysplasia, abnormal mitochondrial structure, mitochondrial dysfunction, and decreased expression of key sarcomeric and mitochondrial genes, rendering them more susceptible to cardiac hypertrophy, vascular wall thickening, cardiac fibrosis, apoptosis, and heart failure induced by Ang II infusion. This study elucidates early-life low dose lead exposure compromises cardiac development and exacerbates second hit-induced cardiac pathological responses in adulthood, which furnishes crucial scientific evidence pertaining to the cardiac toxicity and risk evaluation associated with early-life exposure to lead.

Insulin-like Growth Factor-2 (IGF-2) in Fibrosis

The insulin family consists of insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), their receptors (IR, IGF-1R and IGF-2R), and their binding proteins. All three ligands are involved in cell proliferation, apoptosis, protein synthesis and metabolism due to their homologous sequences and structural similarities. Insulin-like growth factor 2, a member of the insulin family, plays an important role in embryonic development, metabolic disorders, and tumorigenesis by combining with three receptors with different degrees of affinity. The main pathological feature of various fibrotic diseases is the excessive deposition of extracellular matrix (ECM) after tissue and organ damage, which eventually results in organic dysfunction because scar formation replaces tissue parenchyma. As a mitogenic factor, IGF-2 is overexpressed in many fibrotic diseases. It can promote the proliferation of fibroblasts significantly, as well as the production of ECM in a time- and dose-dependent manner. This review aims to describe the expression changes and fibrosis-promoting effects of IGF-2 in the skin, oral cavity, heart, lung, liver, and kidney fibrotic tissues.

Newborn infant skin gene expression: Remarkable differences versus adults

At birth, human infants are poised to survive in harsh, hostile conditions. An understanding of the state of newborn skin development and maturation is key to the maintenance of health, optimum response to injury, healing and disease. The observational study collected full-thickness newborn skin samples from 27 infants at surgery and compared them to skin samples from 43 adult sites protected from ultraviolet radiation exposure, as the standard for stable, mature skin. Transcriptomics profiling and gene set enrichment analysis were performed. Statistical analysis established over 25,000 differentially regulated probe sets, representing 10,647 distinct genes, in infant skin compared to adult skin. Gene set enrichment analysis showed a significant increase in 143 biological processes (adjusted p < 0.01) in infant skin, versus adult skin samples, including extracellular matrix (ECM) organization, cell adhesion, collagen fibril organization and fatty acid metabolic process. ECM organization and ECM structure organization were the biological processes in infant skin with the lowest adjusted P-value. Genes involving epidermal development, immune function, cell differentiation, and hair cycle were overexpressed in adults, representing 101 significantly enriched biological processes (adjusted p < 0.01). The processes with the highest significant difference were skin and epidermal development, e.g., keratinocyte differentiation, keratinization and cornification intermediate filament cytoskeleton organization and hair cycle. Enriched Gene Ontology (GO) biological processes also involved immune function, including antigen processing and presentation. When compared to ultraviolet radiation-protected adult skin, our results provide essential insight into infant skin and its ability to support the newborn's preparedness to survive and flourish, despite the infant's new environment laden with microbes, high oxygen tension and potential irritants. This fundamental knowledge is expected to guide strategies to protect and preserve the features of unperturbed, young skin.

Cardiac pathologies in mouse loss of imprinting models are due to misexpression of H19 long noncoding RNA

Maternal loss of imprinting (LOI) at the H19/IGF2 locus results in biallelic IGF2 and reduced H19 expression and is associated with Beckwith–-Wiedemann syndrome (BWS). We use mouse models for LOI to understand the relative importance of Igf2 and H19 mis-expression in BWS phenotypes. Here we focus on cardiovascular phenotypes and show that neonatal cardiomegaly is exclusively dependent on increased Igf2. Circulating IGF2 binds cardiomyocyte receptors to hyperactivate mTOR signaling, resulting in cellular hyperplasia and hypertrophy. These Igf2-dependent phenotypes are transient: cardiac size returns to normal once Igf2 expression is suppressed postnatally. However, reduced H19 expression is sufficient to cause progressive heart pathologies including fibrosis and reduced ventricular function. In the heart, H19 expression is primarily in endothelial cells (ECs) and regulates EC differentiation both in vivo and in vitro. Finally, we establish novel mouse models to show that cardiac phenotypes depend on H19 lncRNA interactions with Mirlet7 microRNAs.

The developmental transcriptome of the human heart

The human heart develops through complex mechanisms producing morphological and functional changes during gestation. We have recently demonstrated using diffusion tensor MRI that over the relatively short space of 40 days, between 100-140 days gestational age, the ventricular myocardium transforms from a disorganised tissue to the ordered structure characteristic of mature cardiac tissue. However, the genetic basis underpinning this maturation is unclear. Herein, we have used RNA-Seq to establish the developmentally-regulated transcriptome of gene expression in the developing human heart across three gestational ages in the first and second trimester. By comparing 9 weeks gestational age (WGA) with 12 WGA, we find 288 genes show significant differential expression. 305 genes were significantly altered comparing 12 and 16 WGA, and 806 genes differentially expressed between 9 and 16 WGA. Network analysis was used to identify genetic interactions, node properties and gene ontology categories. In summary, we present a comprehensive transcriptomic analysis of human heart development during early gestation, and identify differentially expressed genes during heart development between 9 and 16 weeks, overlapping the first and early second trimester.