Recently, infant cases of acute heart failure attributable to rupture of the mitral chordae tendineae have been reported. However, little is known about the pathogenesis and clinical course of this condition.
The origin and developmental mechanisms underlying coronary vessels are not fully elucidated. Here we show that myocardium-derived angiopoietin-1 (Ang1) is essential for coronary vein formation in the developing heart. Cardiomyocyte-specific Ang1 deletion results in defective formation of the subepicardial coronary veins, but had no significant effect on the formation of intramyocardial coronary arteries. The endothelial cells (ECs) of the sinus venosus (SV) are heterogeneous population, composed of APJ-positive and APJ-negative ECs. Among these, the APJ-negative ECs migrate from the SV into the atrial and ventricular myocardium in Ang1-dependent manner. In addition, Ang1 may positively regulate venous differentiation of the subepicardial APJ-negative ECs in the heart. Consistently, in vitro experiments show that Ang1 indeed promotes venous differentiation of the immature ECs. Collectively, our results indicate that myocardial Ang1 positively regulates coronary vein formation presumably by promoting the proliferation, migration and differentiation of immature ECs derived from the SV.
Fibroblasts can be directly reprogrammed into cardiomyocyte-like cells (iCMs) by overexpression of cardiac transcription factors or microRNAs. However, induction of functional cardiomyocytes is inefficient, and molecular mechanisms of direct reprogramming remain undefined. Here, we demonstrate that addition of miR-133a (miR-133) to Gata4, Mef2c, and Tbx5 (GMT) or GMT plus Mesp1 and Myocd improved cardiac reprogramming from mouse or human fibroblasts by directly repressing Snai1, a master regulator of epithelial-to-mesenchymal transition. MiR-133 overexpression with GMT generated sevenfold more beating iCMs from mouse embryonic fibroblasts and shortened the duration to induce beating cells from 30 to 10 days, compared to GMT alone. Snai1 knockdown suppressed fibroblast genes, upregulated cardiac gene expression, and induced more contracting iCMs with GMT transduction, recapitulating the effects of miR-133 overexpression. In contrast, overexpression of Snai1 in GMT/miR-133-transduced cells maintained fibroblast signatures and inhibited generation of beating iCMs. MiR-133-mediated Snai1 repression was also critical for cardiac reprogramming in adult mouse and human cardiac fibroblasts. Thus, silencing fibroblast signatures, mediated by miR-133/Snai1, is a key molecular roadblock during cardiac reprogramming.
Sodium azide is a strong mutagen which has been successfully employed in mutation breeding of crop plants. In biological systems, it is metabolized to azidoalanine, but further bioactivation to a putative ultimate mutagen as well as the nature of the induced DNA modifications leading to mutations remain elusive. In this study, mutations induced in the CAN1 gene of yeast Saccharomyces cerevisiae by the representative mutagen 3-azido-1,2-propanediol (azidoglycerol, AZG) have been sequenced. Analysis of the forward mutation spectrum to canavanine resistance revealed that AZG induced nearly exclusively G:C to A:T transitions. AZG also induced reversions to tryptophan prototrophy by base-pair substitutions in a dose-dependent manner. This unusual mutational specificity may be shared by other organic azido compounds.
Heart disease remains a leading cause of death worldwide. Owing to the limited regenerative capacity of heart tissue, cardiac regenerative therapy has emerged as an attractive approach. Direct reprogramming of human cardiac fibroblasts (HCFs) into cardiomyocytes may hold great potential for this purpose. We reported previously that induced cardiomyocyte-like cells (iCMs) can be directly generated from mouse cardiac fibroblasts in vitro and vivo by transduction of three transcription factors: Gata4, Mef2c, and Tbx5, collectively termed GMT. In the present study, we sought to determine whether human fibroblasts also could be converted to iCMs by defined factors. Our initial finding that GMT was not sufficient for cardiac induction in HCFs prompted us to screen for additional factors to promote cardiac reprogramming by analyzing multiple cardiac-specific gene induction with quantitative RT-PCR. The addition of Mesp1 and Myocd to GMT up-regulated a broader spectrum of cardiac genes in HCFs more efficiently compared with GMT alone. The HCFs and human dermal fibroblasts transduced with GMT, Mesp1, and Myocd (GMTMM) changed the cell morphology from a spindle shape to a rod-like or polygonal shape, expressed multiple cardiac-specific proteins, increased a broad range of cardiac genes and concomitantly suppressed fibroblast genes, and exhibited spontaneous Ca(2+) oscillations. Moreover, the cells matured to exhibit action potentials and contract synchronously in coculture with murine cardiomyocytes. A 5-ethynyl-2-deoxyuridine assay revealed that the iCMs thus generated do not pass through a mitotic cell state. These findings demonstrate that human fibroblasts can be directly converted to iCMs by defined factors, which may facilitate future applications in regenerative medicine.
We present a case of a 9-year-old boy with nemaline myopathy and dilated cardiomyopathy. The combination of nemaline myopathy and cardiomyopathy is rare, and this is the first reported case of dilated cardiomyopathy associated with childhood-onset nemaline myopathy. A novel mutation, p.W358C, in ACTA1 was detected in this patient. An unusual feature of this case was that the patients cardiac failure developed during early childhood with no delay of gross motor milestones. The use of a ?-blocker did not improve his clinical course, and the patient died 6 months after diagnosis of dilated cardiomyopathy. Congenital nonprogressive nemaline myopathy is not necessarily a benign disorder: deterioration can occur early in the course of dilated cardiomyopathy with neuromuscular disease, and careful clinical evaluation is therefore necessary.
Hypereosinophilic syndrome (HES) is a group of disorders marked by the sustained overproduction of eosinophils, in which eosinophilic infiltration and inflammatory substance release cause damage to multiple organs. Eosinophilic cystitis (EC) is an inflammatory disorder caused by eosinophilic infiltration of the bladder wall. Although EC is often associated with eosinophilia, it has been rarely reported as a manifestation of HES. We report a case of EC as a primary manifestation of HES. The patient was a 27-year-old male with a history of complete intracardiac repair of tetralogy of Fallot who presented with an acute onset of dysuria accompanied by eosinophilia (7.5 × 10(3)/?l, 60% of white blood cells). Ultrasonography and MRI of the bladder showed a bladder mass, a biopsy of which revealed eosinophilic infiltration and degranulation.
Congenital heart defects (CHD) are the most common type of human birth defect and result in significant mortality worldwide. Despite numerous epidemiologic studies in the past decades, few genetic causes have been identified until recently. CHD result from abnormal morphogenesis of the systematic cardiovascular construction during development. Recent advances in molecular embryology, including the discovery of a new source of cardiac progenitor cells termed the second heart field (SHF), have revealed that the heart arises from multiple distinct embryonic origins. Cells derived from the SHF contribute to the development of the cardiac outflow tract, together with the other progenitor cell lineage called cardiac neural crest cells. Numerous cardiac transcription factors regulate these progenitor cells during heart development. Elucidation of the transcriptional network for these cardiac progenitor cells is essential for further understanding cardiac development and providing new insights into the morphogenesis of CHD. This review outlines the recent discoveries of the molecular embryology of the normal heart and the genetic basis of CHD.
Although echo Doppler machines have consistently advanced within a quarter of a century, age related prevalence of valvular regurgitation detected by currently available echo machines remains uncertain. The aim of this study was to investigate the prevalence and correlates of valvular regurgitation in healthy individuals.
Congenital heart defects (CHD) are very common in patients with trisomy 18 (T18) and trisomy 13 (T13). The surgical indication of CHD remains controversial since the natural history of these trisomies is documented to be poor. To investigate the outcome of CHD in patients with T18 and T13, we collected and evaluated clinical data from 134 patients with T18 and 27 patients with T13 through nationwide network of Japanese Society of Pediatric Cardiology and Cardiac Surgery. In patients with T18, 23 (17%) of 134 were alive at this survey. One hundred twenty-six (94%) of 134 patients had CHDs. The most common CHD was ventricular septal defect (VSD, 59%). Sixty-five (52%) of 126 patients with CHD developed pulmonary hypertension (PH). Thirty-two (25%) of 126 patients with CHD underwent cardiac surgery and 18 patients (56%) have survived beyond postoperative period. While palliative surgery was performed in most patients, six cases (19%) underwent intracardiac repair for VSD. Operated patients survived longer than those who did not have surgery (P < 0.01). In patients with T13, 5 (19%) of 27 patients were alive during study period. Twenty-three (85%) of 27 patients had CHD and 13 (57%) of 27 patients had PH. Atrial septal defect was the most common form of CHD (22%). Cardiac surgery was done in 6 (26%) of 23 patients. In this study, approximately a quarter of patients underwent surgery for CHD in both trisomies. Cardiac surgery may improve survival in selected patients with T18.
During pregnancy, progesterone inhibits the growth-promoting actions of estrogen in the uterus. However, the mechanism for this is not clear. The attenuation of estrogen-mediated proliferation of the uterine epithelium by progesterone is a prerequisite for successful implantation. Our study reveals that progesterone-induced expression of the basic helix-loop-helix transcription factor Hand2 in the uterine stroma suppresses the production of several fibroblast growth factors (FGFs) that act as paracrine mediators of mitogenic effects of estrogen on the epithelium. In mouse uteri lacking Hand2, continued induction of these FGFs in the stroma maintains epithelial proliferation and stimulates estrogen-induced pathways, resulting in impaired implantation. Thus, Hand2 is a critical regulator of the uterine stromal-epithelial communication that directs proper steroid regulation conducive for the establishment of pregnancy.
Congenital heart defects (CHDs) occur in 0.5-1% of live births, yet the underlying genetic etiology remains mostly unknown. Recently, a new source of myocardial cells, namely the second heart field (SHF), was discovered in the splanchnic mesoderm. Abnormal development of the SHF leads to a spectrum of outflow tract defects, such as persistent truncus arteriosus and tetralogy of Fallot. Intracellular Ca(2+) signaling is known to be essential for many aspects of heart biology including heart development, but its role in the SHF is uncertain. Here, we analyzed mice deficient for genes encoding inositol 1,4,5-trisphosphate receptors (IP(3)Rs), which are intracellular Ca(2+) release channels on the endo/sarcoplasmic reticulum that mediate Ca(2+) mobilization. Mouse embryos that are double mutant for IP(3)R type 1 and type 3 (IP(3)R1(-/-)IP(3)R3(-/-)) show hypoplasia of the outflow tract and the right ventricle, reduced expression of specific molecular markers and enhanced apoptosis of mesodermal cells in the SHF. Gene expression analyses suggest that IP(3)R-mediated Ca(2+) signaling may involve, at least in part, the Mef2C-Smyd1 pathway, a transcriptional cascade essential for the SHF. These data reveal that IP(3)R type 1 and type 3 may play a redundant role in the development of the SHF.
Cardiogenesis involves the contributions of multiple progenitor pools, including mesoderm-derived cardiac progenitors known as the first and second heart fields. Disruption of genetic pathways regulating individual subsets of cardiac progenitors likely underlies many forms of human cardiac malformations. Hand2 is a member of the basic helix loop helix (bHLH) family of transcription factors and is expressed in numerous cell lineages that contribute to the developing heart. However, the early embryonic lethality of Hand2-null mice has precluded lineage-specific study of its function in myocardial progenitors. Here, we generated and used a floxed allele of Hand2 to ablate its expression in specific cardiac cell populations at defined developmental points. We found that Hand2 expression within the mesoderm-derived second heart field progenitors was required for their survival and deletion in this domain recapitulated the complete Hand2-null phenotype. Loss of Hand2 at later stages of development and in restricted domains of the second heart field revealed a spectrum of cardiac anomalies resembling forms of human congenital heart disease. Molecular analyses of Hand2 mutant cells revealed several genes by which Hand2 may influence expansion of the cardiac progenitors. These findings demonstrate that Hand2 is essential for survival of second heart field progenitors and that the graded loss of Hand2 function in this cardiac progenitor pool can cause a spectrum of congenital heart malformation.
Patients with Down syndrome (DS) and a left-to-right shunt often develop early severe pulmonary hypertension (PH) and pulmonary vascular obstructive disease (PVOD); the pathophysiological mechanisms underlying the development of these complications are yet to be determined. To investigate the mechanisms, we evaluated the biosynthesis of thromboxane (TX) A(2) and prostacyclin (PGI(2)) in four groups of infants, cross-classified as shown below, by measuring the urinary excretion levels of 11-dehydro-TXB(2) and 2,3-dinor-6-keto-PGF(1alpha): DS infants with a left-to-right shunt and PH (D-PH, n = 18), DS infants without congenital heart defect (D-C, n = 8), non-DS infants with a left-to-right shunt and PH (ND-PH, n = 12), and non-DS infants without congenital heart defect (ND-C, n = 22). The urinary excretion ratios of 11-dehydro-TXB(2) to 2,3-dinor-6-keto-PGF(1alpha) in the D-PH, D-C, ND-PH, and ND-C groups were 7.69, 4.71, 2.10, and 2.27, respectively. The ratio of 11-dehydro-TXB(2) to 2,3-dinor-6-keto-PGF(1alpha) was higher in the presence of DS (P < 0.001), independently of the presence of PH (P = 0.297). The predominant biosynthesis of TXA(2) over PGI(2), leading to vasoconstriction, was observed in DS infants, irrespective of the presence/absence of PH. This imbalance in the biosynthesis of vasoactive eicosanoids may account for the rapid progression of PVOD in DS infants with a left-to-right shunt.
Inositol 1,4,5-trisphosphate receptors (IP3R1, 2, and 3) are intracellular Ca2+ release channels that regulate various vital processes. Although the ryanodine receptor type 2, another type of intracellular Ca2+ release channel, has been shown to play a role in embryonic cardiomyocytes, the functions of the IP3Rs in cardiogenesis remain unclear.
Although left ventricular diastolic function has been shown to deteriorate with advancing age, its gender-specific change is unknown. The aim of this study was to investigate age- and gender-specific changes in tissue Doppler-derived left ventricular diastolic index, E.
Congenital heart diseases (CHD) occur in nearly 1% of all live births and are the major cause of infant mortality and morbidity. Although an improved understanding of the genetic causes of CHD would provide insight into the underlying pathobiology, the genetic etiology of most CHD remains unknown. Here we show that mutations in the gene encoding the transcription factor GATA6 cause CHD characteristic of a severe form of cardiac outflow tract (OFT) defect, namely persistent truncus arteriosus (PTA). Two different GATA6 mutations were identified by systematic genetic analysis using DNA from patients with PTA. Genes encoding the neurovascular guiding molecule semaphorin 3C (SEMA3C) and its receptor plexin A2 (PLXNA2) appear to be regulated directly by GATA6, and both GATA6 mutant proteins failed to transactivate these genes. Transgenic analysis further suggests that, in the developing heart, the expression of SEMA3C in the OFT/subpulmonary myocardium and PLXNA2 in the cardiac neural crest contributing to the OFT is dependent on GATA transcription factors. Together, our data implicate mutations in GATA6 as genetic causes of CHD involving OFT development, as a result of the disruption of the direct regulation of semaphorin-plexin signaling.
Congenital heart diseases (CHD) result from abnormal morphogenesis of the embryonic cardiovascular system and usually involve defects in specific structural components of the developing heart and vessels. Therefore, an understanding of "Molecular Embryology", with specific focus on the individual modular steps involved in cardiovascular morphogenesis, is particularly relevant to those wishing to have a better insight into the origin of CHD. Recent advances in molecular embryology suggest that the cardiovascular system arises from multiple distinct embryonic origins, and a population of myocardial precursor cells in the pharyngeal mesoderm anterior to the early heart tube, denoted the "second heart field", has been identified. Discovery of the second heart field has important implications for the interpretation of cardiac outflow tract development and provides new insights into the morphogenesis of CHD.
Recent reports have shown that cardiomyopathy caused by hemochromatosis in severe aplastic anemia is reversible after reduced-intensity allogeneic stem-cell transplantation (RIST). We comprehensively evaluated cardiac and autonomic nerve function to determine whether cardiac dysfunction due to causes other than hemochromatosis is attenuated after RIST. In five patients with cardiac dysfunction before transplant, we analyzed the changes in cardiac and autonomic nerve function after transplant, using electrocardiography (ECG), echocardiography, radionuclide angiography (RNA), serum markers, and heart rate variability (HRV), before and up to 100 days after transplant. There was no significant improvement in cardiac function in any patient and no significant alteration in ECG, echocardiogram, RNA, or serum markers. However, on time-domain analysis of HRV, the SD of normal-to-normal RR intervals (SDNN) and the coefficient of variation of the RR interval (CVRR) decreased significantly 30 and 60 days after transplant (P = 0.04 and 0.01, respectively). Similarly, on frequency-domain analysis of HRV, low and high frequency power (LF and HF) significantly and temporarily decreased (P = 0.003 and 0.03, respectively). Notably, in one patient who had acute heart failure after transplantation, the values of SDNN, CVRR, r-MSSD, LF, and HF at 30 and 60 days after transplantation were the lowest of all the patients. In conclusion, this study suggests that (a) RIST is well-tolerated in patients with cardiac dysfunction, but we cannot expect improvement in cardiac dysfunction due to causes other than hemochromatosis; and (b) monitoring HRV may be useful in predicting cardiac events after RIST.
Muscle is a contractile tissue of animals, dedicated to produce force and cause motion. In higher animals, there are two types of muscle tissue: (a) striated muscle, including all voluntary skeletal muscles and involuntary cardiac muscle, and (b) smooth muscle consisting of involuntary muscles, including those of the viscera, blood vessels, and uterus. Although muscle growth and regeneration take place throughout vertebrate life, the heart is the first organ to start functioning, with continued development until delivery. Skeletal muscles, on the other hand, develop in four successive, temporally distinct phases of embryonic, fetal, neonatal, and adult muscle with the postnatal phase being basically hypertrophy. Unlike terminally differentiated skeletal and cardiac muscles in adults, smooth muscle cells retain their plasticity and the phenotype can change reversibly in response to environmental changes. For the past 20 years, the availability of gene recombination technology directed the focus of studies on transcription factors and signaling molecules, and we would like to review what has been explored by recent studies on myogenesis.
Linezolid, an oxazolidinone antibiotic, exhibits a broad spectrum of activity against Gram-positive bacteria. It has been licensed for adult use in Japan since 2006 for MRSA infections, and has also been used off-label for pediatric patients. At our university hospital, a total of 16 infants and children (including one non-Japanese Asian) were administered linezolid owing to infection with multidrug-resistant Gram-positive bacteria, after consent had been provided. All patients had severe underlying diseases or indications for surgery. Eighty-eight percent of the causal microorganisms were methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-resistant coagulase-negative Staphylococcus and all were sensitive to linezolid. Linezolid was administered because the antecedent anti-MRSA medications were ineffective or contraindicated, or intravenous-to-oral switch therapy was requested owing to cardiac or orthopedic surgical-site infections. The median duration of administration was 13 days (range 3-31 days). The overall efficacy was 91 % (10/11) in those for whom efficacy could be evaluated. Only two patients (both teen-aged) encountered linezolid-related adverse effects (13 %, 2/16). One patient showed elevation of liver enzymes (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]), requiring that administration be withdrawn, but enzyme levels returned to normal after the patient had been switched to vancomycin. The other patient showed transiently decreased platelet counts. Linezolid is considered generally safe and effective for children in Japan, especially for those who cannot use other anti-MRSA medications or those who require oral antibiotics for infections with multidrug-resistant Gram-positive bacteria.
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