Compact Myocardium Research Articles

The simple morphology of the sunfish heart.

The evolutionary conservation of the building plan of the heart suggests this organ is under substantial form-function constraints. Its form varies to such a degree, however, that it questions whether we understand the form-function relations of the heart. A previously published image of the heart of the sunfish (Mola mola, Tetraodontiformes) indicates the presence of an exceptionally simple topology of the chambers. Here, we describe the gross morphology of the sunfish heart (N = 7) because, we assess, this expands the known spectrum of cardiac form that is compatible with function. The usual teleost piscine compartments were present, guarded by valved junctions: sinus venosus, atrium, ventricle, and bulbus arteriosus. Especially, the ventricle was much displaced ventrally and the atrium was dorso-ventrally elongate. The ventricular central cavity exhibited a simple 90-degree curve, or a-quarter circle, and opened into an almost vertical bulbus arteriosus. Overall, the normal piscine S-topology of the cardiac chambers (when seen from the left) appeared distorted to a simpler J-shape. When compared to other fish, including a tetraodontiform boxfish, these highly unusual characters appeared to have evolved recently. The distantly related spotted tinselfish (Xenolepidichthys dalgleishi) resembles sunfish in shape, its heart is almost J-shaped, but the ventricle was sac-like and typically piscine. Surprisingly, the ventricular wall had a comparatively high proportion of compact myocardium, approximately 34%. The relative mass of the sunfish heart was typically piscine, approximately 0.08% of body mass. In conclusion, the sunfish heart may be the least curved cardiac structure described for any fully formed vertebrate.

Neddylation drives myofibrillogenesis in the developing heart.

Neddylation is a highly conserved post-translational modification that plays critical roles in various cellular processes through the modulation of cullins and non-cullin substrates. While neddylation is known to be essential for embryonic development, tumor growth, and organogenesis of different tissues, its role in cardiogenesis remains unexplored. Here, we investigated the role of neddylation in early cardiac development by deleting the gene encoding a regulatory subunit of the NEDD8-specific E1 activating enzyme, Nae1, globally and in a heart-specific fashion via Nkx2-5Cre. Global deletion of Nae1 in mice led to embryonic lethality before embryonic day (E) 8.5, whereas cardiac-specific NAE1 knockout mice died at around E12.5 with pronounced cardiac effusion and peripheral hemorrhage, characteristic of cardiac failure. Histological analysis revealed significant thinning of the compact myocardium and reduced trabeculae in mutant hearts, which were accompanied by reduced cardiomyocyte proliferation. Unbiased transcriptomic analysis identified perturbations in cardiomyocyte proliferation and myofibril architecture in mutant hearts. Subsequent analysis showed that loss of NAE1 disrupted sarcomere assembly dysregulated the expression of several important contractile proteins, and impaired mitochondrial function in the developing heart, which was accompanied by downregulation of key cardiac transcription factors including NKX2-5 and SRF. Collectively, our findings demonstrate the essential role of neddylation in cardiogenesis at least in part by driving cardiomyocyte proliferation and myofibrillogenesis.

Seguimiento Ecocardiográfico De Cambios Anatómicos Del Miocardio De Pacientes Pediátricos con Diagnóstico De Miocardiopatía No Compactada. 2017 – 2021

Background: Non-compaction cardiomyopathy (NCM) is known as the lack of maturation of the myocardium that is evidenced by prominent trabeculations and the presence of recesses in newborns and infants that can manifest clinically as heart failure. The purpose of the research is to evaluate the anatomical development of pediatric patients diagnosed with NCM at an early age. Clinical Case: Retrospective case series study of patients diagnosed with non-compaction cardiomyopathy during the first year of life, confirmed according to Jenni criteria, with echocardiographic follow-up every 6 months, from 2017 - 2021. The patients were diagnosed in the first months of life. life, 3 had associated heart disease, 3 had arrhythmias, 3 died and 1 abandoned the controls at 2 months of age. In the 3 patients who remained, it was evident that the ratio of non-compacted myocardium (NC) / compacted myocardium (C) only remained high in 1 patient. The ejection fraction (EF) improved in all patients, the number of trabeculae only decreased in one patient. Conclusions: Anatomical changes in patients diagnosed with non-compaction cardiomyopathy can evolve to myocardial maturation and improvement in ventricular function.

Pathophysiological and Pedigree Analysis of Left Ventricular Noncompaction in Japanese Macaques (Macaca fuscata).

Left ventricular noncompaction (LVNC) involving genetic mutation is categorized as an unclassified cardiomyopathy, and its diagnostic criteria have not been standardized. This could be because precise animal models of LVNC have not been created in any laboratory animal species. This study aimed to analyze the pathophysiology and familial tendency of LVNC in Japanese macaques. Two Japanese macaques with LVNC, and their parents who were suspected of having cardiac disease, were examined. One macaque with LVNC was examined using chest radiography, echocardiography, cardiac biomarkers, cardiac MRI, and pathologic examination, and the other macaque was examined using chest radiography, echocardiography, and cardiac biomarkers. Their common father and the mother of one of the macaques with LVNC were tested for chest radiography and cardiac biomarkers. Echocardiography revealed a meshwork with trabeculation and deep intertrabecular recesses in all their left ventricular walls. The 2 macaques with LVNC demonstrated a layered appearance of the myocardium, consisting of noncompacted myocardium on the endocardial side and compacted myocardium on the epicardial side, with a noncompacted/compacted ratio of 6.0 and 5.8, respectively. One of the 2 macaques with LVNC (case 1) had elevated levels of troponin I, troponin T, atrial natriuretic peptide, and brain natriuretic peptide. The second macaque with LVNC (case 2) showed blood flow in the intertrabecular recesses on echocardiography. The common father (case 3) of the 2 macaques with LVNC and the mother (case 4) of one of the macaques with LVNC had elevated levels of troponin I and troponin T. In case 1, histopathologic examination revealed fibrous thickening of the endocardium, fibrosis of the myocardial interstitium, myocardial disarray, vacuolar degeneration, anisonucleosis, and necrosis of myocardial cells. This suggests that Japanese macaques could serve as a reliable animal model of human LVNC.

Searching for genetic determinants for left ventricular non-compaction.

Left ventricular non-compaction (LVNC) is still a pathology around which there are numerous controversies regarding the criteria for its diagnosis, presentation, prognosis, and even classification into the appropriate group of diseases. So far, about 190 genes in which mutations may be associated with LVNC have been described, and in each of them, several to several dozen different loci have been discovered. We decided to analyze the frequency of single nucleotide variants (SNVs) in correlation to Petersen's criteria. We retrospectively analyzed the results of cardiac magnetic resonance (CMR) studies. Twenty-three patients who met Petersen's criteria agreed to participate in the research and take blood samples for genetic testing. Next, we prospectively included 24 volunteers who did not meet Petersen's criteria. Petersen's criteria were complied with ratio of non-compacted to compacted myocardium (NC/C) ≥2.3. A total of 47 DNA samples were analyzed based on the selected regions of the following genes: β-myosin heavy chain (MYH7), α-cardiac actin (ACTC1), cardiac troponin T (TNNT2), myosin binding protein-C (MYBPC3), LIM-domain binding protein 3 (LBD3), and taffazin (TAZ). In total, 248 substitutions in exons and introns were obtained for all analyzed samples. No statistically significant differences were detected between the mentioned groups. No significant difference in either downward or upward trends in the number of substitutions in relation to the increasing trabeculation is observed. We indicated differences in the occurrence of the studied SNVs between groups, especially for rs8037241 (3'UTR region of ACTC1) and rs2675686 (LDB3), but they also did not show statistical significance. Although we did not find a significant correlation between the co-occurrence of individual mutations with LVNC, it is worth noting that the presence of one of the four mutations in the range rs8037241 (ACTC1 3'UTR), rs3729998 (TNNT2e. 12), and rs727503240 (MYH7e. 39) increases the risk of LVNC more than 4 times. An inverse association between the number of SNVs and the meeting the Petersen's criteria was demonstrated for studied LDB3 region and rs397516254 in exon 39 of the MYH7 gene. To our knowledge, no studies have been published comparing the prevalence of selected SNVs in a group of healthy subjects and in a group meeting the Petersen criteria for LVNC. Among both completely healthy individuals who did not meet the Petersen criteria for LVNC as well as those with symptoms who met these criteria we found a similar incidence of SNVs in the ACTC1, TNNT2, LDB3 and MYH7 genes segments analyzed. Further studies are required to confirm or exclude "potentially protective" SNV in the 39th exon of MYH7 (rs397516254) and the role of co-occurrence of individual SNVs in rs8037241 (ACTC1 3'UTR), rs3729998 (TNNT2), and rs727503240 (MYH7) for the increase of the risk of LVNC.

Left ventricular trabeculation in Hominidae: divergence of the human cardiac phenotype

Although the gross morphology of the heart is conserved across mammals, subtle interspecific variations exist in the cardiac phenotype, which may reflect evolutionary divergence among closely-related species. Here, we compare the left ventricle (LV) across all extant members of the Hominidae taxon, using 2D echocardiography, to gain insight into the evolution of the human heart. We present compelling evidence that the human LV has diverged away from a more trabeculated phenotype present in all other great apes, towards a ventricular wall with proportionally greater compact myocardium, which was corroborated by post-mortem chimpanzee (Pan troglodytes) hearts. Speckle-tracking echocardiographic analyses identified a negative curvilinear relationship between the degree of trabeculation and LV systolic twist, revealing lower rotational mechanics in the trabeculated non-human great ape LV. This divergent evolution of the human heart may have facilitated the augmentation of cardiac output to support the metabolic and thermoregulatory demands of the human ecological niche.

Local variation in stress response of juvenile anadromous brown trout, Salmo trutta.

Habitat fragmentation may cut off anadromous salmonids from parts of their potential native habitat and separate previously connected populations. Understanding the consequences of this is vital for fish management and prioritization of restoration activities. Here, we show that there is a significant difference in the body morphology, physiological stress response, and aspects contributing to aerobic capacity between juvenile anadromous brown trout, Salmo trutta, collected at a downstream site and an upstream site, separated by 2 km and several challenging stream sections, in a small unfragmented stream system in western Sweden. Following a standardized stress test, there were significant differences between fish from the upstream and downstream sites (plasma cortisol concentration, plasma osmolality, hematocrit, hemoglobin concentration, and mean corpuscular hemoglobin concentration). Plasma glucose concentration did not significantly differ between fish from the two sites. Fish from the upstream site had larger spleen mass, although there was no evidence of differences in ventricle mass or proportion of compact ventricular myocardium. These physiological differences indicate local variation in stress response and highlight the importance of considering local trait variation in river management. If a section of the river becomes fragmented or degraded, and there are differences in the juveniles in different parts of the river, the consequence for the population might be larger than the proportional loss of habitat.

A RARE CASE OF INTERVENTRICULAR SEPTUM DUPLICATION

Abstract Case Report A 62–year–old man, history of hypertension. In 2015, there was suspicion of non–compaction cardiomyopathy, and he underwent cardiac MRI at another facility (report not available). The patient reported palpitations and dyspnea with exertion, leading to a follow–up visit. EKG showed sinus rhythm 90/min, nonspecific intraventricular conduction delay and isolated monomorphic ventricular ectopic beats. Echo revealed a mildly dilated left ventricle (end–diastolic volume 88 ml/m), systolic function at the lower limits of normal (EF 53%), and prominent muscular structures near the posterior interventricular septum (SIV), likely related to anomalies of the papillary muscles (prominent and possibly duplicated posterior–medial papillary muscle). There was apical trabecular protrusion, which did not meet the criteria for non–compaction (NC/C ratio in systole approximately 1), with no other significant findings. The cardiac MRI, performed to assess dilated cardiomyopathy, revealed a conspicuous structural abnormality in the septo–papillary region, located medio–apically and paraseptal–endocardial in the left ventricle. This anomaly lacked evident chordae tendineae with the mitral valve leaflets and exhibited synchronous systo–diastolic motion with the left ventricular wall, suggesting septal duplication. The septal thickness was slightly reduced, particularly in the medio–apical region. Additionally, there was hypertrabeculation of the posterior and lateral walls of the left ventricle, exceeding the threshold for non–compaction (NC/C ratio in end–diastole: 2.6 – normal range: <2.3). Left ventricular mass was normal (mass: 173.52 g; mass/body surface area (BSA): 86.58 g/m). Basal septum, medio–apical septum and medio–apical lateral wallshowed hypokinetic contractility. The left ventricle was dilated (end–diastolic diameter: 55.0 mm; end–systolic diameter: 45.3 mm – end–diastolic volume: 230 ml; stroke volume/BSA: 57.6 ml/m² – EF: 51%). Areas of late gadolinium enhancement (LGE) were observed in the anterior medio–basal septum and at the site of the described structural muscular anomaly, both displaying an intramural non–ischemic pattern. Conclusions The described findings suggest a picture of dilated cardiomyopathy and an associated structural septo–papillary anomaly of uncertain diagnostic interpretation (septum duplication with associated non–compacted myocardium? duplicated posterior–medial papillary muscle with associated non–compacted myocardium?).

The relationship between sarcomerogenesis and the development of tissue organization of the myocardium in embryonic chicken cardiogenesis

Background. The general basis for understanding how the limited range of sarcomere contraction ensures cardiac output during systole is the analysis of the ontogenetic formation and local features of the development of the myofibrillar structure of cardiomyocytes by comparing the phase states of the myocardium. The purpose of the research is to determine phase and topological features and quantitative ultrastructural characteristics of sarcomerogenesis in cardiomyocytes of chicken embryos. Methods. Embryos of Cobb500 crossbred chickens were studied from the beginning of the 6th day to the 21st day of incubation. Ultrastructural features of contractile cardiomyocytes in different areas of ventricular and atrial myocardium in systole and diastole were studied using transmission electron microscopy. Results. At the 29th stage of development of chicken embryos in diastole, immature sarcomeres had different lengths. The average length of sarcomeres was 1.86±0.09 μm in the left ventricle and 1.91±0.21 μm in the right ventricle. At the 36th stage in the state of diastole, a significant increase in the length of sarcomeres was observed in the compact myocardium of the left ventricle and left atrium, while in the right parts of the heart, the increase in Z-Z distance was less active. In the right units of the heart, sarcomeres with unequal lengths were more often found in the compact myocardium and in the trabeculae. In different areas of the myolamella and trabeculae, the degree of relaxation of sarcomeres during simulation of maximum diastole was not the same. Incomplete relaxation of sarcomeres was noted in the initial and final sections of the muscle plates. In the middle part of the trabeculae, the length of the sarcomeres was significantly longer (1.82±0.04 μm), and in the intermediate (main) part of the muscle plates of the compact ventricular myocardium, the sarcomeres were 10.4% (p<0.05) longer, than in their basis. Conclusion. By the end of prenatal cardiogenesis, the tangential orientation of the Z-discs of myofibrils and the shape of cardiomyocytes in systole was formed and strengthened due to the mutual displacement of neighboring myolamella during the counter-directional rotation of the basal and apical parts of the left ventricle during the shortening of sarcomeres to 1.83±0.04 μm. In the right ventricle and atrial myocardium, systolic contraction did not change the orthogonal orientation of telophragms and intercalated discs when sarcomeres were shortened to 1.79-1.84 μm. In the state of diastole, the orthogonal orientation of Z-discs is characteristic of contractile cardiomyocytes of all chambers when the length of sarcomeres reaches 2.17±0.07 μm in the intermediate part of the myolamella of both ventricles, 2.12±0.13 μm in the middle part of atrial and ventricular trabeculae, 2.02±0.10 μm at the base of trabeculae of all chambers and muscle plates of both ventricles.

Formation and development of lamellar histoarchitecture of the ventricular myocardium of chick embryos

Background. The existence of several models of the myolamellar structure of the ventricular myocardium, which currently has a number of contradictory provisions, reflects the need for a reasonable integration of the results of different methods. Under these circumstances, the study of those ontogenetic mechanisms that are responsible for the formation and development of the myolamellar architecture of the myocardium is of great interest. The purpose of the study is to determine the ontogenetic transformations of the embryonic chicken heart that ensure the formation and development of the myolamellar structure of the ventricular myocardium. Methods. The work examined the embryos of Cobb500 cross chickens from the beginning of the 10th day to the 21st day of incubation. The lamellar organization of the ventricular myocardium was studied using light and transmission electron microscopy. Results. Starting from the 36th stage according to NN (the beginning of the 10th day of incubation), the active development of the stromal component was observed in the heart of chicken embryos, which led to the division of the tissue of the compact ventricular myocardium into groups of muscle fibers in the form of narrow elongated flat plates containing thicker than 3 to 5 rows of cardiomyocytes. At the 41st and 43rd stages of development, active development of the intercellular matrix and division of the myocardium mass into muscle plates continued as part of the compact ventricular myocardium. The intercellular spaces within the plates narrowed, and between the myolamellae, the perimysium accumulated elements of the microcirculatory bed, functionally active fibroblasts, a large amount of amorphous substance, and bundles of formed collagen fibers. At the final stages of embryogenesis, the muscle plates of the left ventricle acquired a pronounced spiral orientation with a gradual displacement of the long axis of the muscle fibers in the direction from the apex of the ventricle to its base. In the wall of the right ventricle, the location of the myolamella acquired a transverse oblique-circular orientation. Conclusion. A comparison of the structure and geometry of the myolamella made it possible to reveal that starting from the 38th stage of development in the left ventricle, the conditions for the translational-rotational mechanism of chamber contraction were formed and increased, in which the formation of the difference between the systolic and diastolic volumes of the left ventricle is ensured not only by the longitudinal apico-basal vector compression of the cavity, but also by mutual sliding of spirally oriented plates in the ventricular wall. In right ventricle, the contraction mechanism is based on the longitudinal-circular compression of the chamber in accordance with the oblique-circular orientation of the muscle fibers in the composition of the myolamella without displacement in the state of systole.

Left ventricular function assessment including or excluding trabeculations in left ventricular non-compaction, a preliminary case-control cardiac magnetic resonance study.

Functional assessment of compact myocardium and hypertrabeculations in left ventricular non-compaction (LVNC) is underestimated with regards to the morphological spectrum of disease. We aimed to assess whether measuring concurrently left ventricular (LV) volume, mass and ejection fraction (LVEF) with and without trabeculation inclusion on cine magnetic resonance (cineMR) could help diagnose patients with LVNC by comparison to normal individuals with an excess of myocardial trabeculations. This retrospective single center magnetic resonance imaging study (Bichat University Hospital) of 67 consecutive patients with echocardiographic hypertrabeculations seen at echocardiography between March 2011 and October 2018 included 30 patients with known LVNC and 16 control subjects with simple hypertrabeculations (non-compact/compact (NC/C) ratio between 1.8 and 2.2, trabeculations involving 10% to 17% of the left ventricle) using steady-state free precession (SSFP) cine sequences in the standard views. LV volumes, mass and LVEF were measured with and without trabeculation inclusion using CVI42 software. Follow-up was studied in 20 patients and 14 controls. Functional parameters were compared using Student's paired t-test. Pearson product moment correlation coefficients were calculated. Bland-Altman analysis determined the inter- and intra-reader functional data reproducibility. When excluding the trabeculations (i.e. non-compacted myocardium) from measurements, LVEF was within normal ranges both in patients and controls, while it increased by 9.8%±1.6% in LVNC and decreased by 10.9%±1.4% in controls when trabeculae were included in the endocardial contours (P<0.0001). The overall myocardial mass remained stable according to the diastolic or systolic phase in LVNC whereas it significantly decreased in controls. Depending whether trabeculations were included or not, LVEF measurements were significantly different between patients with LVNC and controls. These distinctive measurements might be used as an adjunctive clinical tool to help confirm the diagnosis of LVNC.

The changing morphology of the ventricular walls of mouse and human with increasing gestation.

That the highly trabeculated ventricular walls of the developing embryos transform to the arrangement during the fetal stages, when the mural architecture is dominated by the thickness of the compact myocardium, has been explained by the coalescence of trabeculations, often erroneously described as 'compaction'. Recent data, however, support differential rates of growth of the trabecular and compact layers as the major driver of change. Here, these processes were assessed quantitatively and visualized in standardized views. We used a larger dataset than has previously been available of mouse hearts, covering the period from embryonic day 10.5 to postnatal day 3, supported by images from human hearts. The volume of the trabecular layer increased throughout development, in contrast to what would be expected had there been 'compaction'. During the transition from embryonic to fetal life, the rapid growth of the compact layer diminished the proportion of trabeculations. Similarly, great expansion of the central cavity reduced the proportion of the total cavity made up of intertrabecular recesses. Illustrations of the hearts with the median value of left ventricular trabeculation confirm a pronounced growth of the compact wall, with prominence of the central cavity. This corresponds, in morphological terms, to a reduction in the extent of the trabecular layer. Similar observations were made in the human hearts. We conclude that it is a period of comparatively slow growth of the trabecular layer, rather than so-called compaction, that is the major determinant of the changing morphology of the ventricular walls of both mouse and human hearts.

Soft-Matter Physics Provides New Insights on Myocardial Architecture: Automatic and Quantitative Identification of Topological Defects in the Trabecular Myocardium.

This article is the third in our series dedicated to the analysis of cardiac myoarchitecture as a nematic chiral liquid crystal (NCLC). Previously, we introduced the concept of topological defects (disclinations) and focused on their visual identification inside the compact myocardium. Herein, we investigate these using a mathematical and automated algorithm for the reproducible identification of a larger panel of topological defects throughout the myocardium of 13 perinatal and 11 early infant hearts. This algorithm identified an average of 29 ± 11 topological defects per slice with a 2D topological charge of m = +1/2 and an average of 27 ± 10 topological defects per slice with a 2D topological charge of m = -1/2. The excess of defects per slice with a 2D topological charge of m = +1/2 was statistically significant (p < 0.001). There was no significant difference in the distribution of defects with a 2D topological charge of m = +1/2 and m = -1/2 between perinatal and early infant hearts. These defects were mostly arranged in pairs, as expected in nematics, and located inside the trabecular myocardium. When isolated, defects with a 2D topological charge of m = +1/2 were located near the luminal extremity of the trabeculae and those with a 2D topological charge of m = -1/2 were located at the anterior and posterior part of the interventricular septum. These findings constitute an advance in the characterization of the deep cardiac myoarchitecture for application in developmental and pathological studies.

A fetal rat model of ventricular noncompaction caused by intrauterine hyperglycemia

BackgroundThis study aims to develop a fetal rat model of ventricular noncompaction (NVM) using streptozotocin (STZ)-induced gestational hyperglycemia and compare it with a retinoic acid (RA) model. MethodsFemale SD rats were categorized into STZ, RA, and normal control (NC) groups. The STZ group was given a high-fat diet pre-pregnancy and 35 mg/kg of 2% STZ postpregnancy. The RA group received a 90 mg/kg dose of RA on day 13 postpregnancy. Embryonic myocardial morphology was analyzed through HE staining, and embryonic cardiomyocyte ultrastructures were studied using electron microscopy. Diagnoses of NVM were based on a ratio of noncompact myocardium (N) to compact myocardium (C) >1.4, accompanied by thick myocardial trabeculae and a thin myocardial compaction layer. Kruskal-Wallis test determined N/C ratio differences among groups. ResultsBoth STZ and RA groups displayed significant NVM characteristics. The left ventricular (LV) N/C in the STZ, RA, and NC groups were 1.983 (1.423-3.527), 1.640 (1.197-2.895), and 0.927 (0.806-1.087), respectively, with a statistically significant difference (P<0.001). The right ventricular (RV) N/C in the STZ, RA, and NC groups were 2.097 (1.364-3.081), 1.897 (1.337-2.662), and 0.869 (0.732-1.022), respectively, with a significant difference (P<0.001). Electron microscopy highlighted marked endoplasmic reticulum swelling in embryonic cardiomyocytes from both STZ and RA groups. ConclusionOur model underscores the pivotal role of an adverse intrauterine developmental environment in the onset of NVM. This insight holds significant implications for future studies exploring the pathogenesis of NVM.

Nonsense Variant PRDM16-Q187X Causes Impaired Myocardial Development and TGF-β Signaling Resulting in Noncompaction Cardiomyopathy in Humans and Mice.

PRDM16 plays a role in myocardial development through TGF-β (transforming growth factor-beta) signaling. Recent evidence suggests that loss of PRDM16 expression is associated with cardiomyopathy development in mice, although its role in human cardiomyopathy development is unclear. This study aims to determine the impact of PRDM16 loss-of-function variants on cardiomyopathy in humans. Individuals with PRDM16 variants were identified and consented. Induced pluripotent stem cell-derived cardiomyocytes were generated from a proband hosting a Q187X nonsense variant as an in vitro model and underwent proliferative and transcriptional analyses. CRISPR (clustered regularly interspaced short palindromic repeats)-mediated knock-in mouse model hosting the Prdm16Q187X allele was generated and subjected to ECG, histological, and transcriptional analysis. We report 2 probands with loss-of-function PRDM16 variants and pediatric left ventricular noncompaction cardiomyopathy. One proband hosts a PRDM16-Q187X variant with left ventricular noncompaction cardiomyopathy and demonstrated infant-onset heart failure, which was selected for further study. Induced pluripotent stem cell-derived cardiomyocytes prepared from the PRDM16-Q187X proband demonstrated a statistically significant impairment in myocyte proliferation and increased apoptosis associated with transcriptional dysregulation of genes implicated in cardiac maturation, including TGF-β-associated transcripts. Homozygous Prdm16Q187X/Q187X mice demonstrated an underdeveloped compact myocardium and were embryonically lethal. Heterozygous Prdm16Q187X/WT mice demonstrated significantly smaller ventricular dimensions, heightened fibrosis, and age-dependent loss of TGF-β expression. Mechanistic studies were undertaken in H9c2 cardiomyoblasts to show that PRDM16 binds TGFB3 promoter and represses its transcription. Novel loss-of-function PRDM16 variant impairs myocardial development resulting in noncompaction cardiomyopathy in humans and mice associated with altered TGF-β signaling.

Pentachloronitrobenzene disturbed murine ventricular wall development by inhibiting cardiomyocyte proliferation via Hec1 downregulation

Exposure to the organochlorine fungicide pentachloronitrobenzene (PCNB) causes developmental abnormalities, including cardiac malformation. However, the molecular mechanism of PCNB cardiotoxicity remains elusive. We found that oral administration of PCNB to pregnant mice induced a hypoplastic wall with significant thinning of the compact myocardium in the developing hearts. PCNB significantly downregulates the expression of Hec1, a member of the NDC80 kinetochore complex, resulting in aberrant spindles, chromosome missegregation and an arrest in cardiomyocyte proliferation. Cardiac-specific ablation of Hec1 sharply inhibits cardiomyocyte proliferation, leading to thinning of the compact myocardium and embryonic lethality. Mechanistically, we found that activating transcription factor 3 (ATF3) transactivates Hec1 expression. Either HEC1 or ATF3 overexpression significantly rescues mitotic defects and restore the decreased proliferative ability of cardiomyocytes caused by PCNB exposure. Our findings highlight that maternal PCNB exposure disrupts embryonic cardiac function by inhibiting cardiomyocyte proliferation and interfering with ventricular wall development, partially attributed to the downregulation of the Atf3-Hec1 axis.

Long-term stress induced cortisol downregulation, growth reduction and cardiac remodeling in Atlantic salmon.

Stress and elevated plasma cortisol in salmonids have been linked with pathological remodeling of the heart and deterioration of fitness and welfare. However, these associations were based on biomarkers that fail to provide a retrospective view of stress. This study is the first whereby the association of long-term stress, using scale cortisol as a chronic stress biomarker, with cardiac morphology and growth performance of wild Atlantic salmon (Salmo salar) is made. Growth, heart morphology, plasma and scale cortisol levels, and expression of genes involved in cortisol regulation of the hypothalamic-pituitary-interrenal axis of undisturbed fish (control) were compared with those of fish exposed daily to stress for 8 weeks. Though scale cortisol levels showed a time-dependent accumulation in both groups, plasma and scale cortisol levels of stress group fish were 29.1% and 25.0% lower than those of control fish, respectively. These results correlated with the overall upregulation of stress-axis genes involved in the systemic negative feedback of cortisol, and local feedback via 11β-hydroxysteroid dehydrogenases, glucocorticoid and mineralocorticoid receptors in the stress treatment at the hypothalamus and pituitary level. These lower cortisol levels were, however, counterintuitive in terms of the growth performance as stress group fish grew 33.7% slower than control fish, which probably influenced the 8.4% increase in relative ventricle mass in the stress group. Though compact myocardium area between the treatments was comparable, these parameters showed significant linear correlations with scale cortisol levels, indicating the involvement of chronic stress in cardiac remodeling. These findings underscore the importance of scale cortisol as biomarker when associating chronic stress with long-term processes including cardiac remodeling.

Role and prognostic relevance of cardiac magnetic resonance imaging in the assessment of left ventricular non-compaction cardiomyopathy: review and meta-analysis

Abstract Background Left ventricular non-compaction (LVNC) is a heterogeneous myocardial disorder characterized by prominent myocardial trabeculation with deep inter-trabecular recesses, thin epicardial layer of compacted myocardium and extensive non-compacted inner muscular layer. Although several diagnostic criteria have been proposed, prediction of major adverse cardiovascular and cerebrovascular events (MACCE) still remains challenging in patients with LVNC. Objectives Objectives of our study were to perform systemic review and meta-analysis of published literature evaluating role and prognostic significance of the late gadolinium enhancement (LGE) in cardiac magnetic resonance imaging (CMR) study, its association with MACCE and characteristics of CMR derived feature-tracking (FT) strain analysis in patients with LVNC. Methods The objectives, literature search strategies, inclusion and exclusion criteria, outcome measurements, and methods of statistical analysis were analyzed according to an established protocol of the cochrane collaboration steps and meta-analysis of observational studies in epidemiology recommendations (MOOSE). Case control studies with evaluated prevalence of LGE in LVNC cardiomyopathy patients with and without MACCE and studies comparing FT strain: left ventricular global longitudinal (LV GLS), global circumferential (GCS) and global radial (GRS) strain between patients with and without LVNC has been included in the analysis. Results A total of 936 papers were collected according to our searching criteria, of those 9 studies including 416 LVNC cardiomyopathy patients with MACCE and 673 LVNC patients without MACCE and with evaluated LGE (including three studies with LVNC and heart failure), also 6 studies including 267 LVNC patients and 283 controls with evaluated FT LV GLS, GCS and GRS (measured in four studies) were selected. LGE was more frequently observed in LVNC patients with MACCE as compared to those without MACCE [RR (95 %CI) 2.52 (1.63 to 3.88); p&amp;lt;0.00001] (Fig.1). FT LV GLS was significantly more affected in LVNC patients compared to controls (St. mean difference (95 %CI): 1.40 (0.69 to 2.11); p&amp;lt;0.00001], as well as GCS and GRS (Fig. 2). Conclusions In patients with LVNC evaluated with CMR, LGE shows association with adverse cardiovascular and cerebrovascular events. CMR deformation indices: FT LV GLS, GCS, and GRS are significantly affected in patients with LVNC as compared to controls. This new CMR technique may be a complementary tool for timely detection and differentiation of LVNC cardiomyopathy and to avoid life threatening adverse events.Figure 1Figure 2

Abstract 12088: Left Ventricular Non-Compaction, Coronary Artery Fistula, and Infective Endocarditis: A Rare Combination

Description of Case: A 48-year-old man underwent echocardiography for multifocal subacute infarctions found on brain MRI. No intracardiac shunts were found, but prominent LV trabeculae raised suspicion of LV non-compaction (LVNC). LV ejection fraction was 53%, and LV volume was within upper-normal range. Cardiac MRI confirmed these findings, although non-compacted:compacted myocardium ratio was 1.9. (Panel A-B) A right coronary artery to LV fistula was also diagnosed. (Panel C-D) The patient was followed-up uneventfully, but 10 months later was admitted after a generalized seizure episode. Brain MRI detected multiple new hemorrhagic infarcts, and echocardiography revealed a 10.8mmх10.1mm mobile mass and high-speed diastolic flow near the basolateral LV wall. (Panel E-F) Gemella morbillorum was identified on two blood cultures. The patient underwent surgery for fistula closure and vegetation resection. Vegetation pathology and culture however was negative for bacterial growth. Paroxysmal atrial fibrillation was also detected, before discharge with full recovery. Discussion: LVNC and coronary artery fistula (CAF) are both caused by arrest in embryonic myocardial compaction. Despite a hypothetical common origin, reports of co-occurrence are extremely rare. This is the first to report the association of a mild form of LVNC and a single large CAF. This is also the first to report infective endocarditis due to CAF by G. morbillorum . G. morbillorum infective endocarditis is rare, subacute in course, and causes significant destruction. The extensive, prolonged embolism found here has not been reported in other cases of CAF-associated infective endocarditis and may be due to G. morbillorum .

Nrg1 Regulates Cardiomyocyte Migration and Cell Cycle in Ventricular Development.

Cardiac ventricles provide the contractile force of the beating heart throughout life. How the primitive endocardium-layered myocardial projections called trabeculae form and mature into the adult ventricles is of great interest for biology and regenerative medicine. Trabeculation is dependent on the signaling protein Nrg1 (neuregulin-1). However, the mechanism of action of Nrg1 and its role in ventricular wall maturation are poorly understood. We investigated the functions and downstream mechanisms of Nrg1 signaling during ventricular chamber development using confocal imaging, transcriptomics, and biochemical approaches in mice with cardiac-specific inactivation or overexpression of Nrg1. Analysis of cardiac-specific Nrg1 mutant mice showed that the transcriptional program underlying cardiomyocyte-oriented cell division and trabeculae formation depends on endocardial Nrg1 to myocardial ErbB2 (erb-b2 receptor tyrosine kinase 2) signaling and phospho-Erk (phosphorylated extracellular signal-regulated kinase; pErk) activation. Early endothelial loss of Nrg1 and reduced pErk activation diminished cardiomyocyte Pard3 and Crumbs2 (Crumbs Cell Polarity Complex Component 2) protein and altered cytoskeletal gene expression and organization. These alterations are associated with abnormal gene expression related to mitotic spindle organization and a shift in cardiomyocyte division orientation. Nrg1 is crucial for trabecular growth and ventricular wall thickening by regulating an epithelial-to-mesenchymal transition-like process in cardiomyocytes involving migration, adhesion, cytoskeletal actin turnover, and timely progression through the cell cycle G2/M phase. Ectopic cardiac Nrg1 overexpression and high pErk signaling caused S-phase arrest, sustained high epithelial-to-mesenchymal transition-like gene expression, and prolonged trabeculation, blocking compact myocardium maturation. Myocardial trabecular patterning alterations resulting from above- or below-normal Nrg1-dependent pErk activation were concomitant with sarcomere actin cytoskeleton disorganization. The Nrg1 loss- and gain-of-function transcriptomes were enriched for Yap1 (yes-associated protein-1) gene signatures, identifying Yap1 as a potential downstream effector. Furthermore, biochemical and imaging data reveal that Nrg1 influences pErk activation and Yap1 nuclear-cytoplasmic distribution during trabeculation. These data establish the Nrg1-ErbB2/ErbB4-Erk axis as a crucial regulator of cardiomyocyte cell cycle progression and migration during ventricular development.