Apical Contraction Research Articles

The zonula adherens matura redefines the apical junction of intestinal epithelia

Cell-cell apical junctions of epithelia consist of multiprotein complexes that organize as belts regulating cell-cell adhesion, permeability, and mechanical tension: the tight junction (zonula occludens), the zonula adherens (ZA), and the macula adherens. The prevailing dogma is that at the ZA, E-cadherin and catenins are lined with F-actin bundles that support and transmit mechanical tension between cells. Using super-resolution microscopy on human intestinal biopsies and Caco-2 cells, we show that two distinct multiprotein belts are basal of the tight junctions as the intestinal epithelia mature. The most apical is populated with nectins/afadin and lined with F-actin; the second is populated with E-cad/catenins. We name this dual-belt architecture the zonula adherens matura. We find that the apical contraction apparatus and the dual-belt organization rely on afadin expression. Our study provides a revised description of epithelial cell-cell junctions and identifies a module regulating the mechanics of epithelia.

Development and Application of an Optogenetic Manipulation System to Suppress Actomyosin Activity in Ciona Epidermis.

Studying the generation of biomechanical force and how this force drives cell and tissue morphogenesis is challenging for understanding the mechanical mechanisms underlying embryogenesis. Actomyosin has been demonstrated to be the main source of intracellular force generation that drives membrane and cell contractility, thus playing a vital role in multi-organ formation in ascidian Ciona embryogenesis. However, manipulation of actomyosin at the subcellular level is impossible in Ciona because of the lack of technical tools and approaches. In this study, we designed and developed a myosin light chain phosphatase fused with a light-oxygen-voltage flavoprotein from Botrytis cinerea (MLCP-BcLOV4) as an optogenetics tool to control actomyosin contractility activity in the Ciona larva epidermis. We first validated the light-dependent membrane localization and regulatory efficiency on mechanical forces of the MLCP-BcLOV4 system as well as the optimum light intensity that activated the system in HeLa cells. Then, we applied the optimized MLCP-BcLOV4 system in Ciona larval epidermal cells to realize the regulation of membrane elongation at the subcellular level. Moreover, we successfully applied this system on the process of apical contraction during atrial siphon invagination in Ciona larvae. Our results showed that the activity of phosphorylated myosin on the apical surface of atrial siphon primordium cells was suppressed and apical contractility was disrupted, resulting in the failure of the invagination process. Thus, we established an effective technique and system that provide a powerful approach in the study of the biomechanical mechanisms driving morphogenesis in marine organisms.

Continuum description of confluent tissues with spatial heterogeneous activity.

A continuum description is built to characterize the stationary and transient deformations of confluent tissues subject to heterogeneous activities. By defining a coarse-grained texture matrix field to represent the shape and size of cells, we derive the coarse-grained stress tensor for the vertex model. Activity in the tissue takes the form of inhomogeneous apical contractions, which can be modeled as reductions of the vertex model reference areas or perimeters representing activity in the medial and perimeter regions of the cells, respectively. For medial activity, the extra stress is just an isotropic pressure, while for perimeter activity, it also has a deviatoric component, which is aligned with the texture matrix. The predictions of the continuum description are compared with the average spatiotemporal deformations obtained in simulations of the vertex model subject to localized apical contractions, showing an excellent agreement, even if the active patch is as small as one cell. The fluctuations around the average are more prominent when the activity is in the medial region due to the lack of negative active shape feedback, which, coupled with the confluent property, increases cellular shape and size variations.

572 INTRAMYOCARDIAL CALCIFICATION IN APICAL HYPERTROPHIC CARDIOMYOPATHY ASSESSED USING MULTIMODALITY IMAGING: OUR CASE SERIES

Abstract Introduction Apical Hypertrophic Cardiomyopathy (ApHCM) characterized by persistent diastolic apical contraction results in dynamic apical small-vessel obstruction with microvascular ischemia. Of note, endomyocardial fibrosis (EMF) and calcification are described only in few patients. Case presentation We report 5 cases of ApHCM with apical intramyocardial calcification. They presented characteristic ECG pattern and fibrosis at echocardiogram. All patients presented a preserved ejection fraction (EF), except for one patient with mild reduced EF. Global longitudinal strain was reduced in 3 patients. Diastolic dysfunction was evidenced in 3 patients. Right ventricle involvement was detected in one patient only.On cardiac magnetic resonance, a superficial hypo-intense component, compatible with calcium and a deep layer featured by late gadolinium enhancement (LGE) related to fibrotic tissue, were revealed. LGE was present in all of patients in the apex. One patient presented an apical aneurysm, with high ESC-SCD risk score and ICD implantation. Conclusion EMF pathologic hallmarks were the endocardium and myocardium scarring, evolving to dystrophic calcification. In clinical practice, only a minority of ApHCM patients develops EMF and calcifications. Our clinical series is the largest one in literature. Analyzing patients’ history, a microvascular inflammatory trigger was evident in all of them, particularly severe chronic kidney disease, diabetes, high degree obesity, malaria infection, peripheral microangiopathy and form of thalassemia. This series could demonstrate the pathophysiological relation between apical fibrosis, calcification and microvascular ischemia due to hypertrophy and inflammatory conditions coexistence. A broader case series could evaluate any correlation with their long-term outcome and management strategies.

Embryo-scale epithelial buckling forms a propagating furrow that initiates gastrulation

Cell apical constriction driven by actomyosin contraction forces is a conserved mechanism during tissue folding in embryo development. While much is now understood of the molecular mechanism responsible for apical constriction and of the tissue-scale integration of the ensuing in-plane deformations, it is still not clear if apical actomyosin contraction forces are necessary or sufficient per se to drive tissue folding. To tackle this question, we use the Drosophila embryo model system that forms a furrow on the ventral side, initiating mesoderm internalization. Past computational models support the idea that cell apical contraction forces may not be sufficient and that active or passive cell apico-basal forces may be necessary to drive cell wedging leading to tissue furrowing. By using 3D computational modelling and in toto embryo image analysis and manipulation, we now challenge this idea and show that embryo-scale force balance at the tissue surface, rather than cell-autonomous shape changes, is necessary and sufficient to drive a buckling of the epithelial surface forming a furrow which propagates and initiates embryo gastrulation.

The cell polarity determinant Dlg1 facilitates epithelial invagination by promoting tissue-scale mechanical coordination.

Epithelial folding mediated by apical constriction serves as a fundamental mechanism to convert flat epithelial sheets into multilayered structures. It remains unknown whether additional mechanical inputs are required for apical constriction-mediated folding. Using Drosophila mesoderm invagination as a model, we identified an important role for the non-constricting, lateral mesodermal cells adjacent to the constriction domain ('flanking cells') in facilitating epithelial folding. We found that depletion of the basolateral determinant Dlg1 disrupts the transition between apical constriction and invagination without affecting the rate of apical constriction. Strikingly, the observed delay in invagination is associated with ineffective apical myosin contractions in the flanking cells that lead to overstretching of their apical domain. The defects in the flanking cells impede ventral-directed movement of the lateral ectoderm, suggesting reduced mechanical coupling between tissues. Specifically disrupting the flanking cells in wild-type embryos by laser ablation or optogenetic depletion of cortical actin is sufficient to delay the apical constriction-to-invagination transition. Our findings indicate that effective mesoderm invagination requires intact flanking cells and suggest a role for tissue-scale mechanical coupling during epithelial folding.

Feasibility of blood speckle imaging parameters as predictors of intracavitary thrombus in apical aneurysm

Abstract Funding Acknowledgements Type of funding sources: None. Introduction In patients with apical aneurysm, left ventricular thrombus (LVT) is a major complication associated with systemic embolism. Likely, abnormalities in apical wall contraction produce stagnant flow which leads to the thrombus formation. Currently, there is a lack of knowledge about predictors of thrombus in such patients. However, new imaging techniques might be able to identify flow properties useful for risk stratification. Specifically, blood speckle imaging (BSI), a technology based on high-frame rate ultrasound, is a promising pattern-matching technique that could allow a comprehensive assessment of blood flow in patients with apical aneurysms (1,2). Purpose The aim of the study was to demonstrate the feasibility of obtaining quantitative and qualitative measurements with BSI in patients with apical aneurysms and to explore which parameters may be associated with LVT. Methods We examined cases of patients with apical aneurysm and LVT studied in our tertiary center. In order to exclude from our analysis the pro-inflammatory effects of the acute event, patients with thrombus formation within the first month after the ischemic event were excluded. Patients with current presence of thrombus were also discarded. A control group of patients with apical aneurysm but without history of LVT was included. A basic 2-dimensional echocardiography study was obtained, along with BSI images. BSI acquisitions were performed with a 29 cm/s (2.5 mHz) scale. Data regarding vortex flow were collected, including its presence, area, length, besides area without BSI vectors (Image 1). All measures were indexed by telediastolic left ventricular volume. Results Eight patients with apical aneurysms were enrolled in the study, four of them with history of LVT. Although in patients with history of thrombus a larger vortex area was found (Table 1), none of the differences in the BSI parameters was statistically significant. Conclusion This study shows for the first time the feasibility of BSI for characterizing complex flow patterns such as vortex in patients with apical aneurysms. Explorations in larger cohorts of patients are needed to prove significant findings with this technology in the future. Abstract Figure. Image 1 Abstract TABLE 1

Human neural tube morphogenesis in vitro by geometric constraints.

Understanding human organ formation is a scientific challenge with far-reaching medical implications1,2. Three-dimensional stem-cell cultures have provided insights into human cell differentiation3,4. However, current approaches use scaffold-free stem-cell aggregates, which develop non-reproducible tissue shapes and variable cell-fate patterns. This limits their capacity to recapitulate organ formation. Here we present a chip-based culture system that enables self-organization of micropatterned stem cells into precise three-dimensional cell-fate patterns and organ shapes. We use this system to recreate neural tube folding from human stem cells in a dish. Upon neural induction5,6, neural ectoderm folds into a millimetre-long neural tube covered with non-neural ectoderm. Folding occurs at 90% fidelity, and anatomically resembles the developing human neural tube. We find that neural and non-neural ectoderm are necessary and sufficient for folding morphogenesis. We identify two mechanisms drive folding: (1) apical contraction of neural ectoderm, and (2) basal adhesion mediated via extracellular matrix synthesis by non-neural ectoderm. Targeting these two mechanisms using drugs leads to morphological defects similar to neural tube defects. Finally, we show that neural tissue width determines neural tube shape, suggesting that morphology along the anterior-posterior axis depends on neural ectoderm geometry in addition to molecular gradients7. Our approach provides anew route to the study of human organ morphogenesis in health and disease.

Cell fate coordinates mechano-osmotic forces in intestinal crypt formation.

Intestinal organoids derived from single cells undergo complex crypt-villus patterning and morphogenesis. However, the nature and coordination of the underlying forces remains poorly characterized. Through light-sheet microscopy and large-scale imaging quantification, we demonstrate that crypt formation coincides with stark lumen volume reduction. We develop a 3D biophysical model to computationally screen different mechanical scenarios of crypt morphogenesis. Combining this with live-imaging data and multiple mechanical perturbations, we show that actomyosin-driven crypt apical contraction and villus basal tension work synergistically with lumen volume reduction to drive crypt morphogenesis, and demonstrate the existence of a critical point in differential tensions above which crypt morphology becomes robust to volume changes. Finally, we identified a sodium/glucose cotransporter specific to differentiated enterocytes that modulates lumen volume reduction via cell swelling in villus region. Altogether, our study uncovers the cellular basis of how cell fate modulates osmotic and actomyosin forces to coordinate robust morphogenesis.

Left ventricular contraction patterns in Takotsubo Syndrome and their correlation with long-term clinical outcome.

BackgroundTakotsubo Syndrome (TTS) is diagnosed in 1–2% of all patients presenting with acute coronary syndrome. Next to the typical apical manifestation, other locations of left ventricular contraction abnormality are possible, but their relationship to patient characteristics, clinical correlates as well as long-term outcome are poorly understood.Methods & resultsWe retrospectively analyzed 126 patients presenting TTS. Cases were categorized according to left ventricular contraction abnormality patterns: typical apical pattern (71%, n = 89) vs. atypical patterns (29%, n = 37). Cases with typical TTS showed significantly higher levels of troponin I (3.12 ng/ml vs. 1.32 ng/ml, p = 0.013) and creatin kinase (CK) on admission (461 (±1207)U/l vs. 173 (±177) U/l, p = 0.03) as well as peak CK (973 (±2860)U/l vs. 301 (±328) U/l, p = 0.03) and more often ischemia related ECG changes (p = 0.02). Follow-up data was available for 85% of the patients. Median FU time was 4.4 years (IQR 1.4–7.7 years). All-cause mortality during follow-up was 39%, with no significant difference between patients with typical or atypical TTS (43% vs. 29%, p = 0.17). In multivariate logistic regression analysis, only anemia was predictive for long-term mortality (OR 3.93, 95%CI 1.02–2.08, p = 0.015). The majority of surviving patients (69%) reported good quality of life, even though only 56% reported being symptom-free.ConclusionPatients with TTS have poor long-term prognosis with an overall mortality of 39.1% within 4 years and nearly half of all patients report persisting symptoms. Even though the apical contraction pattern is associated with higher elevation of serum markers for myocardial damage, it was not associated with higher long-term mortality.

Buckling of an Epithelium Growing under Spherical Confinement.

SummaryMany organs are formed through folding of an epithelium. This change in shape is usually attributed to tissue heterogeneities, for example, local apical contraction. In contrast, compressive stresses have been proposed to fold a homogeneous epithelium by buckling. While buckling is an appealing mechanism, demonstrating that it underlies folding requires measurement of the stress field and the material properties of the tissue, which are currently inaccessible in vivo. Here, we show that monolayers of identical cells proliferating on the inner surface of elastic spherical shells can spontaneously fold. By measuring the elastic deformation of the shell, we infer the forces acting within the monolayer and its elastic modulus. Using analytical and numerical theories linking forces to shape, we find that buckling quantitatively accounts for the shape changes of our monolayers. Our study shows that forces arising from epithelial growth in three-dimensional confinement are sufficient to drive folding by buckling.

P815Tako-Tsubo Cardiomyopathy: clinical correlations of typical and atypical left ventricular contraction patterns

Abstract Background Takotsubo cardiomyopathy (TCM) is diagnosed in 1–2% of all patients presenting with acute coronary syndrome (ACS). Clinical differences in individuals presenting with either the typical (apical) or atypical (midventricular, basal and focal) localization of left ventricular contraction abnormalities are not well understood. Methods We retrospectively analyzed 102 consecutive patients diagnosed with TCM based on clinical presentation, coronary angiography, and laevocardiography. Patients with different contraction abnormality patterns were compared regarding sex, clinical presentation, trigger for TCM, LV-function and LV enddiastolic pressure (LVEDP) as well as coronary artery disease. Results Of all TCM 102 patients, 69 (68%) presented with the typical pattern of apical contraction abnormality. 33 patients (32%) had an atypical pattern: 22 (22%) with the midventricular type, 2 (2%) with the basal type and 9 (9%) with a focal type. There was no difference in sex distribution among the different types of TCM (female: typical 86% vs atypical 85% p=0.83). Presentation as a ST-elevation ACS was more common in patients with atypical compared to typical TCM (21% vs. 17%; p=0.85), but without statistical significance. Cardiogenic shock (typical 6% vs atypical 3%; p=0.91) as well as intra-hospital death (typical 3% vs atypical 3%; p=0.56) were rare in both types. A trigger was not more common in patients with typical TCM (58% vs atypical 55%; p=0.91). The trigger was more often physical in typical (73%) and atypical TCM (78%) than psychological, but the distribution did not differ between the two types (p=0.92). 83.6% of the patients showed an impaired LV-EF. Median LV-EF in patients with typical TCM (35% (IQR 25–40)) tended to be lower than in patients with atypical TCM (40% (IQR 25–40); p=0.63; LV-EF ≤30% typical TCM 45% vs. atypical TCM 39%; p=0.75). In 72% (73/102) of the patients the LVEDP was determined. In 75% (55/73) the LVEDP was elevated (>15mmHg). LVEDP tended to be more often elevated in patients with typical TCM (83% vs. atypical 52%; p=0.11). Extent of coronary artery disease did not differ in the different types of TCM. Coronary stenosis >50% was rare (typical TCM 20% vs atypical TCM 9%; p=0.26), whereas exclusion of coronary artery disease was common in both types (typical TCM 71%; atypical TCM 76%; p=0.79). Conclusion While an apical contraction anomaly is the most common type of presentation in TCM, atypical contraction patterns are found in 32% of the patients. Overall, psychological triggers are not found as frequently in TCM as previously described. Patients with typical and atypical TCM do not differ in clinical presentation, LV-EF, LVEDP and extent of coronary artery disease.

Author Correction: Basolateral protrusion and apical contraction cooperatively drive Drosophila germ-band extension.

In the version of this Article originally published, the authors cited the wrong articles for reference numbers 18, 30 and 31; the correct ones are listed below. Furthermore, four additional references have been inserted at numbers 37, 38, 39 and 40 as in the list below, and the original references 37-40 have been renumbered. These corrections have been made in the online versions of the Article.

Jak-Stat pathway induces Drosophila follicle elongation by a gradient of apical contractility.

Tissue elongation and its control by spatiotemporal signals is a major developmental question. Currently, it is thought that Drosophila ovarian follicular epithelium elongation requires the planar polarization of the basal domain cytoskeleton and of the extra-cellular matrix, associated with a dynamic process of rotation around the anteroposterior axis. Here we show, by careful kinetic analysis of fat2 mutants, that neither basal planar polarization nor rotation is required during a first phase of follicle elongation. Conversely, a JAK-STAT signaling gradient from each follicle pole orients early elongation. JAK-STAT controls apical pulsatile contractions, and Myosin II activity inhibition affects both pulses and early elongation. Early elongation is associated with apical constriction at the poles and with oriented cell rearrangements, but without any visible planar cell polarization of the apical domain. Thus, a morphogen gradient can trigger tissue elongation through a control of cell pulsing and without a planar cell polarity requirement.

Ultra Fast Contractions and Emergent Dynamics in a Living Active Solid - The Epithelium of the Primitive Animal Trichoplax adhaerens

Apical contractions in epithelial sheets are often associated with embryogenesis. Conventionally, these contractions are slow and precisely controlled in space and time, patterning the shape and form of a developing embryo. In this work we report the discovery of ultra-fast epithelial contractions (50% cell area in 1 second, at least an order of magnitude faster) in a “simple” primitive marine invertebrate, Trichoplax adherence, lacking neurons or muscles. Using theoretical calculations, we demonstrate that this speed can still be explained by existing models of acto-myosin contractility and load reduction. We show that tissue architecture is reducing the load on the molecular motors at work. Furthermore, live imaging of the whole animal in vivo reveals emerging contraction patterns, including propagating radial and axial waves. We hypothesize a new role of cellular contractions in epithelium - keeping tissue integrity and enabling resilience to rupture via “active cohesion”. Studying this primitive epithelium highlights a novel unstudied realm in active soft matter.

The non-canonical Wnt-PCP pathway shapes the mouse caudal neural plate.

The last stage of neural tube (NT) formation involves closure of the caudal neural plate (NP), an embryonic structure formed by neuromesodermal progenitors and newly differentiated cells that becomes incorporated into the NT. Here, we show in mouse that, as cell specification progresses, neuromesodermal progenitors and their progeny undergo significant changes in shape prior to their incorporation into the NT. The caudo-rostral progression towards differentiation is coupled to a gradual reliance on a unique combination of complex mechanisms that drive tissue folding, involving pulses of apical actomyosin contraction and planar polarised cell rearrangements, all of which are regulated by the Wnt-PCP pathway. Indeed, when this pathway is disrupted, either chemically or genetically, the polarisation and morphology of cells within the entire caudal NP is disturbed, producing delays in NT closure. The most severe disruptions of this pathway prevent caudal NT closure and result in spina bifida. In addition, a decrease in Vangl2 gene dosage also appears to promote more rapid progression towards a neural fate, but not the specification of more neural cells.

Ineffective and prolonged apical contraction is associated with chest pain and ischaemia in apical hypertrophic cardiomyopathy

To investigate the hypothesis that persistence of apical contraction into diastole is linked to reduced myocardial perfusion and chest pain. Apical hypertrophic cardiomyopathy (HCM) is defined by left ventricular (LV) hypertrophy predominantly of the apex. Hyperdynamic contractility resulting in obliteration of the apical cavity is often present. Apical HCM can lead to drug-refractory chest pain. We retrospectively studied 126 subjects; 76 with apical HCM and 50 controls (31 with asymmetrical septal hypertrophy (ASH) and 19 with non-cardiac chest pain and culprit free angiograms and structurally normal hearts). Perfusion cardiac magnetic resonance imaging (CMR) scans were assessed for myocardial perfusion reserve index (MPRi), late gadolinium enhancement (LGE), LV volumes (muscle and cavity) and regional contractile persistence (apex, mid and basal LV). In apical HCM, apical MPRi was lower than in normal and ASH controls (p<0.05). In apical HCM, duration of contractile persistence was associated with lower MPRi (p<0.01) and chest pain (p<0.05). In multivariate regression, contractile persistence was independently associated with chest pain (p<0.01) and reduced MPRi (p<0.001). In apical HCM, regional contractile persistence is associated with impaired myocardial perfusion and chest pain. As apical myocardium makes limited contributions to stroke volume, apical contractility is also largely ineffective. Interventions to reduce apical contraction and/or muscle mass are potential therapies for improving symptoms without reducing cardiac output.

P23-5 - Improvement of Refractory Heart Failure Using CRT in a Patient With QRS Duration Less Than 120 ms: A Case Report

A 50-year-old woman who had a cardiomegaly and low left ventricular ejection fraction, left ventricular end diastolic volume 231 mL, left ventricular end systolic volume 181 mL, LVEF 18%, BNP 488 pg/dL, NYHA class 4 was diagnosed heart failure. She has dyspnea on effort and orthopnea for a couple of months. She had a sinus rhythm and did not have a coronary artery disease. Although she was given optimal medical therapies, her symptoms were not getting better. She was in stage C heart failure and we decided to do cardiac resynchronization therapy. Her QRS duration was 114 m sec and she did not have a typical echocardiographic findings of dyssynchrony. Two weeks after implantation, she could discharged from hospital and six months later, she had no symptoms of heart failure. Her left ventricle became smaller and dramatically improved ejection fraction, left ventricular end diastolic volume 184 mL, left ventricular end systolic volume 98 mL, LVEF 47%, BNP 5.4 pg/dL, NYHA class 2. In this case, correction of the intraventricular dyssynchrony may not be the key to improve heart failure. Before CRT implantation, apical circumferential strain was relatively preserved. After CRT implantation, circumferential strain and longitudinal strain of apical long axis view and 4ch view were improved. The propriety of apical contraction might be related to the myocardial response to electrical stimulation.

Basolateral protrusion and apical contraction cooperatively drive Drosophila germband extension

Basolateral protrusion and apical contraction cooperatively drive Drosophila germband extension

Basolateral protrusion and apical contraction cooperatively drive Drosophila germ-band extension.

Throughout development, tissues undergo complex morphological changes, resulting from cellular mechanics that evolve over time and in three-dimensional space. During Drosophila germ-band extension (GBE), cell intercalation is the key mechanism for tissue extension, and the associated apical junction remodelling is driven by polarized myosin-II-dependent contraction. However, the contribution of the basolateral cellular mechanics to GBE remains poorly understood. Here, we characterize how cells coordinate their shape from the apical to the basal side during rosette formation, a hallmark of cell intercalation. Basolateral rosette formation is driven by cells mostly located at the dorsal/ventral part of the rosette (D/V cells). These cells exhibit actin-rich wedge-shaped basolateral protrusions and migrate towards each other. Surprisingly, the formation of basolateral rosettes precedes that of the apical rosettes. Basolateral rosette formation is independent of apical contractility, but requires Rac1-dependent protrusive motility. Furthermore, we identified Src42A as a regulator of basolateral rosette formation. Our data show that in addition to apical contraction, active cell migration driven by basolateral protrusions plays a pivotal role in rosette formation and contributes toGBE.