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Modulation of alpha-actin and alpha-actinin proteins in cardiomyocytes by retinoic acid during development.

Early heart development is known to be sensitive to retinoid concentrations. Although the influence of retinoids on cardiac morphogenesis has been described previously, the effect of retinoids on cardiomyocyte differentiation during development has not been characterized. We quantified the effects of the retinoic acids all-trans RA and 13-cis RA on alpha-actin and alpha-actinin at the subcellular level in cultures of chick embryo cardiomyocytes obtained from Hamburger and Hamilton's (HH) stage 22, 32 and 40 embryos. The retinoids increased the concentration of alpha-actin and alpha-actinin in the cytoplasmic and cytoskeletal fractions of cells at all three stages of development. The effect was greatest in cardiomyocytes treated for 24 h with all-trans RA and in cells from HH22 embryos. The greatest increases in alpha-actin concentration occurred in the cytoskeletal fraction of HH22 cells cultured for 24 h with all-trans or 13-cis RA, whereas the greatest increases in alpha-actinin were found in the cytoplasmic fraction of HH22 cells exposed to retinoids for 24 h. We conclude that retinoic acid plays a role in the reorganization of the pattern of sarcomeric protein expression during cardiomyocyte differentiation.

Actinin↗

Distribution of beta-1 integrin in the developing rat heart.

Cell-cell and cell-matrix interactions play critical roles in various developmental processes including differentiation, proliferation, and migration. Members of the integrin family of cell surface components are important mediators of these cell-extracellular matrix (ECM) contacts or interactions. The ECM provides signals to individual cells essential for development and differentiation and plays essential roles in establishing and maintaining the complex structure of the vertebrate heart. Integrins provide a fundamental link for transduction of developmental signals to cells. Integrin expression by cardiac myocytes is altered during neonatal heart development and disease; however, little is known regarding the spatial and temporal patterns of integrin expression during embryonic and fetal heart development. Essential to understanding the role of integrins in the organization of the heart, the present studies have localized beta-1 integrin protein and mRNA in fetal and neonatal rat hearts. Beta-1 integrin is predominantly found in regions of remodeling (trabeculae) in the early heart (10-13 days of gestation). Later in development (15 days of gestation onward), beta-1 integrin is abundant in regions containing an elaborate ECM, such as the valves. These studies further support the hypothesis that the expressions of integrins and ECM are coordinately regulated in the developing heart.

Animals↗

The use of myocytes as a model for developing successful heart preservation solutions.

The development of a successful method to preserve the heart for relatively long periods (24-48 hr) requires demonstrating successful orthotopic transplantation and long-term survival after preservation. There are, however, multiple variables that may affect the quality of heart preservation, and it is nearly impossible to systematically study all the variables in this complicated model. One model that may be useful to study how preservation parameters affect heart cell preservation is the isolated myocyte preparation. In this study myocytes were isolated from the rabbit heart and the effects of up to 24 hr cold storage on viability measured to determine if this would be a suitable preservation model. Myocytes were stored in various preservation solutions including; EuroCollins (EC), two cardioplegic solutions (Stanford [ST] and Bretschneider solution [HTK]) and the University of Wisconsin solution (UW) with or without the addition of polyethylene glycol. The viability of myocytes was judged by measuring the effects of preservation and rewarming after preservation on cellular morphology (percent rod-shaped cells), ATP concentration, and LDH release. Myocytes preserved in the cardioplegic solutions were least well preserved after 12 and 24 hr storage, as judged by the loss of rod-shaped morphology and lower ATP concentration. Preservation in EC resulted in a decrease in the percent rod-shaped cells after 12 hr and 24 hr storage that was greater than obtained in the UW solutions. The best preservation of myocyte morphology and highest content of ATP was obtained in myocytes stored in the UW solutions, especially those containing PEG. The myocyte model of heart preservation shows a loss of cell integrity that is related to the preservation solution (HTK greater than ST greater than EC greater than UW-PEG) and these results are similar to what has been shown in the past with other models of heart preservation. Thus the myocyte model appears to be a useful method to test how many preservation solutions and preservation variables affect heart cell metabolism. In the future, results from these types of studies may find use in developing improved heart preservation solutions for testing in the orthotopic transplant model.

Adenosine↗

Mitochondrial component of the phosphorylcreatine shuttle is enhanced during rat heart perinatal development.

Aerobic metabolism is enhanced during perinatal heart development in parallel with increased cardiac function. The mitochondrial component of the phosphorylcreatine shuttle is important in providing energy for contraction and was examined in weanling and adult rat left ventricle. Creatine kinase activity was enhanced in tissue homogenate and purified cardiac myocytes of adults. Mitochondrial analyses attribute this enhancement to increased creatine kinase activity per milligram mitochondrial protein. Other enzymatic markers of mitochondrial function are not enhanced in activity during perinatal heart growth. The unique response of creatine kinase points to the shuttle mechanism and of mitochondrial creatine kinase, in particular, as a major contributor to heart functional regulation.

3-Hydroxyacyl CoA Dehydrogenases↗

[Variability in the diameter of the capillaries of the human heart during development].

Seventy-eight hearts from persons, who had not suffered any cardiovascular disorders during their life time, have been studied. Microcirculatory bed vessels are revealed by impregnation with silver nitrate after V. V. Kuprianov. The values of the capillary diameters obtained are mathematically treated using T. H. Bayes formula. Periods of individual development of the heart are defined when a high functional activity of the capillary bed of the auricles and ventricles is noted. Evidently, this is one of the factors contributing to development of the cardiac ischemic disease.

Adolescent↗

Microinjecting recombinant rainbow trout Ea4-peptide of pro-IGF-I into zebrafish embryos causes abnormal development in heart, red blood cells, and vasculature.

E-peptides and mature insulin-like growth factors (IGFs) are produced from pre-pro-IGFs during post-translational processing and co-secreted into the circulation. Previously, we reported that introduction of a transgene encoding the secreted form of rainbow trout (rt) Ea4-peptide or human (h) Eb-peptide into newly fertilized eggs of medaka (Oryzias latipes) and zebrafish (Danio rerio) resulted in developmental defects in heart, red blood cells and vasculature. In addition to vasculature and red blood cell developmental defects, multiple phenocopies of heart developmental defects categorized by developmental arrest at cardiomyocyte, heart tube and heart looping stages were also observed. These results raise a question of whether rtEa4- or hEb-peptide exerts pleiotropic inhibitory effects on heart, vasculature and red blood cell development in fish embryos. To answer this question, various amounts of recombinant rtEa4-peptide were microinjected into zebrafish eggs at 1.5, 2.5 and 5.5 h post-fertilization (hpf). Although a dose-dependent developmental defect in heart, vasculature and red blood cells was observed in embryos microinjected with rtEa4-peptide at 1.5 and 2.5 hpf, the heart development in all of the microinjected embryos was arrested at the cardiomyocyte stage. Furthermore, the mRNA levels of Nkx2.5, GATA5, VEGF, GATA1 and GATA2 genes in defective embryos were significantly reduced by rtEa4-peptide. These results confirm our previous findings that rtEa4- or hEb-peptide exhibits pleiotropic effects in inhibiting heart, vasculature and red blood cell development in zebrafish embryos.

Animals↗

Formation of myocardium after the initial development of the linear heart tube.

Well after formation of the primary linear heart tube, the mesenchymal cardiac septa become largely myocardial, and myocardial sleeves are formed along the caval and pulmonary veins. This second wave of myocardium formation can be envisioned to be the result of recruitment of cardiomyocytes by differentiation from flanking mesenchyme and/or by migration from existing myocardium (myocardialization). As a first step to elucidate the underlying mechanism, we studied in chicken heart development the formation of myocardial cells within intra- and extracardiac mesenchymal structures. We show that the second wave of myocardium formation proceeds in a caudal-to-cranial gradient in vivo. At the venous pole, loosely arranged networks of cardiomyocytes are observed in the dorsal mesocardium from H/H19 onward, in the atrioventricular cushion region from H/H26 onward, and in the proximal outflow tract (conus) from H/H29 onward. The process is completed at H/H stage 43. Subsequently, we determined the potential of the different cardiac compartments to form myocardial networks in a 3D in vitro culture assay. This analysis showed that the competency to form myocardial networks in vitro is a characteristic of the myocardium that is flanked by intra- or extracardiac mesenchyme, i.e., the inflow tract, atrioventricular canal, and outflow tract. These cardiac compartments can be induced to form myocardial networks by a temporally released or secreted signal that is similar throughout the entire heart. Atrial and ventricular compartments are not competent and do not produce the inducer. Moreover, cardiac cushion mesenchyme was found to be able to (trans-)differentiate into cardiomyocytes in the in vitro culture assay. The combined observations suggest that a common mechanism and molecular regulatory pathway underlies the recruitment of mesodermal cells into the cardiogenic lineage during this second wave of myocardium formation through the entire heart.

Animals↗

Nodose placode provides ectomesenchyme to the developing chick heart in the absence of cardiac neural crest.

The cardiac neural crest provides both ectomesenchyme and parasympathetic postganglionic neurons to the developing heart. Ablation of cardiac neural crest results in persistent truncus arteriosus, a condition in which the conotruncal and aorticopulmonary septa do not form in the developing heart. Parasympathetic postganglionic neurons are abundantly present in hearts with persistent truncus arteriosus, which indicates a "regeneration" of the neural component of the cardiac neural crest without comparable restitution of the ectomesenchymal component. The neural component has been shown to be provided by cells from the nodose placode following ablation of the cardiac neural crest. This investigation has shown that ectomesenchymal cells are also supplied to a limited extent by the nodose placode which normally has no ectomesenchymal derivatives. Although placode-derived ectomesenchyme helps to strengthen the wall of the cardiac outflow vessel, it is not competent to induce conotruncal and aorticopulmonary septal closure.

Animals↗

Third heart sound and elevated jugular venous pressure as markers of the subsequent development of heart failure in patients with asymptomatic left ventricular dysfunction.

PURPOSE: To determine the independent prognostic value of a third heart sound (S(3)) and elevated jugular venous pressure in patients with asymptomatic left ventricular dysfunction. METHODS: We performed a post hoc analysis of 4102 participants from the Studies of Left Ventricular Dysfunction (SOLVD) prevention trial. In that trial, participants with asymptomatic or minimally symptomatic left ventricular dysfunction (New York Association class I or II, left ventricular ejection fraction < or =0.35, no treatment for heart failure) were allocated randomly to enalapril or placebo and followed for a mean (+/- SD) of 34 +/- 14 months. The presence of an S(3) and elevated jugular venous pressure was ascertained by physical examination at study enrollment. We used multivariate proportional hazards models to determine whether these physical examination findings were associated with the development of heart failure, a prespecified endpoint of the SOLVD prevention trial. RESULTS: At baseline, 209 subjects (5.1%) had an S(3) and 70 (1.7%) had elevated jugular venous pressure. Heart failure developed in 1044 subjects (25.5%). After adjusting for other markers of disease severity, an S(3) was associated with an increased risk of heart failure (relative risk [RR] = 1.38; 95% confidence interval [CI]: 1.09 to 1.73; P = 0.007) and the composite endpoint of death or development of heart failure (RR = 1.34; 95% CI: 1.09 to 1.64; P = 0.005). Elevated jugular venous pressure was also associated with these outcomes in multivariate models. CONCLUSION: The physical examination provides prognostic information among patients with asymptomatic or minimally symptomatic left ventricular dysfunction.

Analysis of Variance↗

[Studies on morphogenesis and visualization of the early embryonic heart with regard to the development of conotruncal heart defects].

Most congenital cardiovascular malformations have their origins during early morphogenesis, and some forms of adult-onset cardiovascular disease also arise during embryonic development. Conotruncal heart defects comprise a major category of congenital heart disease and are found in children with a relative high frequency. These defects are associated with a high mortality risk in utero, and after postnatal surgical repair; embryologically they are linked with dextroposed aorta, which is an anomaly of the ventricular outflow tract with malalignment of the great arteries. The etiology and pathogenesis of dextroposed aorta is not known but is thought to be due to abnormal looping and/or incorrect "wedging" of the outflow tract (i.e., wedged positioning of the aorta between the atrioventricular valves) during early heart development. We have studied the morphology and visual development of the embryonic heart in an animal model of dextropsed aorta in a series of experiments to determine possible mechanisms for dextropositioning of the aorta. At this, we have employed besides established methods for analysis of anatomy and pathology (morphological studies, cardiac morphometry, histology, scanning electron microscopy and immunhistochemistry) also new imaging techniques (videocinephotography and time-lapse studies with a digital high-speed video camera, confocal and scanning electron microscopy, optical coherence tomography (OCT) and magnetic resonance microscopy (MRM) for 3D reconstruction of the heart) to achieve a better visualization of normal and pathological changes during heart development. The paper at hand summarizes the results of these studies.

Adult↗

Vinculin knockout results in heart and brain defects during embryonic development.

The vinculin gene codes for a cytoskeletal protein, found in focal adhesion plaques and in cell-cell adherens junctions. Vinculin was inactivated by homologous recombination using a targeting vector in embryonic stem (ES) cells. The heterozygous ES cells were introduced into mice by established procedures to produce heterozygous animals that were normal and fertile. No homozygous vinculin-/- embryos were born and analyses during the gestational period showed that the vinculin null embryos were small and abnormal from day E8 but some survived until E10. The most prominent defect was lack of midline fusion of the rostral neural tube, producing a cranial bilobular appearance and attenuation of cranial and spinal nerve development. Heart development was curtailed at E9.5, with severely reduced and akinetic myocardial and endocardial structures. Mutant embryos were 30-40% smaller, somites and limbs were retarded and ectodermal tissues were sparse and fragile. Fibroblasts (MEF) isolated from mutant embryos were shown to have reduced adhesion to fibronectin, vitronectin, laminin and collagen compared to wild-type levels. In addition, migration rates over these substrata were two-fold higher and the level of focal adhesion kinase (FAK) activity was three-fold higher. We conclude that vinculin is necessary for normal embryonic development, probably because of its role in the regulation of cell adhesion and locomotion, cell behaviors essential for normal embryonic morphogenesis, although specific roles in neural and cardiac development cannot be ruled out.

Animals↗

Targeted cardiac expression of soluble Fas prevents the development of heart failure in mice with cardiac-specific expression of MCP-1.

Monocyte chemoattractant protein-1 (MCP-1) plays a crucial role in initiating coronary heart disease by recruiting monocytes/macrophages to the vessel wall. Transgenic mice with cardiac-specific expression of MCP-1 manifest cardiac inflammation and develop heart failure. The pathways mediating the detrimental effects of MCP-1 expression have not been defined. We postulate that the Fas ligand (FasL) derived from the infiltrating mononuclear cells causes death of cardiac cells resulting in the development of heart failure. Here, we tested this hypothesis by determining whether inhibition of FasL function through cardiac-specific expression of soluble Fas (sFas) would rescue the MCP-1 transgenic mice from developing heart failure. We generated mice with cardiac-specific expression of sFas and double homozygous transgenic mice that express both MCP-1 and sFas. Cardiac-specific expression of sFas in MCP mice, in fact, inhibited apoptosis of infiltrating mononuclear cells, normalized circulating C-reactive protein (CRP) levels, and prevented macrophage activation as well as production of proinflammatory cytokines, tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 in the hearts. sFas expression resulted in restoration of cardiac structure, preservation of cardiac function, and a significant prolongation of survival of MCP mice. These results demonstrate that FasL released from infiltrating mononuclear cells plays a critical role in the detrimental effects of MCP-1 expression, and suggest that Fas/FasL signaling represents a novel therapeutic target for heart failure.

Animals↗

Expression of mRNAs for neurotrophins and their receptors in developing rat heart.

Because the neurotrophic system has not been systematically studied in developing heart, we studied the expression of mRNAs for neurotrophins and their high- and low-affinity receptors by radioactive in situ hybridization in the rat heart from embryonic day 9 (E9) to parturition. The neurotrophin-3 (NT-3) transcripts were seen in the group of Leu-7 immunoreactive cells in the ventricular region from E11 to parturition, suggesting that NT-3 is expressed in the part of the developing conduction system, mRNAs for truncated trk receptors, trkC.TK- and trkB.T1, were expressed in the outflow tract at E12 and in the walls of developing aorta and pulmonary trunk from E13 to parturition, whereas the mRNA for catalytic trkC.TK+ was revealed in the walls of aorta and pulmonary trunk from E13 to parturition and in the cardiac ganglion neurons from E14 to adult stage. Transcripts for low-affinity neurotrophin receptor (p75) were transiently seen in the distal outflow tract from E11 to E13, declining by E14. At E18, p75 transcripts were also seen in the cardiac ganglia. Transcripts for nerve growth factor, neurotrophin-4/5, trkA, or trkB.TK+ were not detected. Expression of NT-3 mRNA in the developing conduction system and of trkC.TK + mRNA in the cardiac neurons suggests a role for NT-3 in the innervation of the conduction system. Expression of trkC.TK+ in the wall of aorta and pulmonary trunk suggests that NT-3 also may affect the development of the smooth muscle cells.

Aging↗