Remodeling Events Research Articles

Abstract A009: Genetic disruption of CAPNS1 impedes triple-negative breast cancer metastasis: A case for selective calpain-1/2 inhibitors

Abstract Calpains are a family of 15 calcium-activated cysteine proteases that have emerged as potential therapeutic targets in triple negative breast cancer (TNBC). They regulate the function of their substrates via limited proteolytic processing and are involved in both pro- and anti-apoptotic signaling pathways, as well as membrane-cytoskeletal remodeling events associated with cell migration and invasion. The most well-understood members of the calpain family are the classical calpain-1 and calpain-2 isoforms, which are ubiquitously expressed heterodimers each consisting of a large catalytic subunit, encoded by the capn1 and capn2 genes, respectively, and a common small regulatory subunit encoded by capns1. Overexpression of calpain-1 and calpain-2 has been associated with shorter survival in HER2+ breast cancer and TNBC, respectively. We hypothesize that inhibition of calpain-1 and calpain-2 may be exploited to improve tumor response to cytotoxic chemotherapy and suppress metastasis. CRISPR-Cas9 mediated knockout of capns1 in AC2M2 mouse mammary carcinoma cells, which results in a loss of both calpain-1 and calpain-2 activity, disrupts migration and invasion in vitro and impedes lung metastasis in tail vein and orthotopic engraftment mouse models. Calpain knockout also sensitizes AC2M2 cells to the microtubule stabilizing drug paclitaxel, and preliminary results suggest that cancer cell intrinsic calpain depletion may prevent neoadjuvant chemotherapy-induced metastasis. To explore potential off-target effects associated with systemic calpain inhibition, we have established a novel transgenic mouse with conditional deletion of capns1 in its hematopoietic stem cell lineage. By comparing the immune profiles of wild-type and capns1 knockout mice, we aim to better understand how calpain inhibitors will affect various immune cell populations and their respective functions. We plan to extend this understanding to anticancer immunity by conducting tumor immunophenotyping experiments in syngeneic orthotopic engraftment models using wild-type and capns1 knockout mice. At present, no clinically relevant calpain inhibitors are available. However, using genetic approaches, we have validated calpain-1 and calpain-2 as relevant therapeutic targets in TNBC, providing rationale for the development of selective calpain inhibitors. Citation Format: Danielle Harper, Ivan Shapovalov, Samantha Cockburn, Jenny Min, Yan Gao, Peter A. Greer. Genetic disruption of CAPNS1 impedes triple-negative breast cancer metastasis: A case for selective calpain-1/2 inhibitors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Optimizing Therapeutic Efficacy and Tolerability through Cancer Chemistry; 2024 Dec 9-11; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(12_Suppl):Abstract nr A009.

Long Noncoding RNA Function in Smooth Muscle Cell Plasticity and Atherosclerosis.

In the healthy mature artery, vascular cells, including endothelial cells, smooth muscle cells (SMCs), and fibroblasts are organized in different layers, performing specific functions. SMCs located in the media are in a differentiated state and exhibit a contractile phenotype. However, in response to vascular injury within the intima, stimuli from activated endothelial cells and recruited inflammatory cells reach SMCs and induce a series of remodeling events in them, known as phenotypic switching. Indeed, SMCs retain a certain degree of plasticity and are able to transdifferentiate into other cell types that are crucial for both the formation and development of atherosclerotic lesions. Because of their highly cell-specific expression profiles and their widely recognized contribution to physiological and disease-related biological processes, long noncoding RNAs have received increasing attention in atherosclerosis research. Dynamic fluctuations in their expression have been implicated in the regulation of SMC identity. Sophisticated technologies are now available to allow researchers to access single-cell transcriptomes and study long noncoding RNA function with unprecedented precision. Here, we discuss the state of the art of long noncoding RNAs regulation of SMC phenotypic switching, describing the methodologies used to approach this issue and evaluating the therapeutic perspectives of exploiting long noncoding RNAs as targets in atherosclerosis.

RANK drives structured intestinal epithelial expansion during pregnancy.

During reproduction, multiple species such as insects and all mammals undergo extensive physiological and morphological adaptions to ensure health and survival of the mother and optimal development of the offspring. Here we report that the intestinal epithelium undergoes expansion during pregnancy and lactation in mammals. This enlargement of the intestinal surface area results in a novel geometry of expanded villi. Receptor activator of nuclear factor-κΒ (RANK, encoded by TNFRSF11A) and its ligand RANKL were identified as a molecular pathway involved in this villous expansion of the small intestine in vivo in mice and in intestinal mouse and human organoids. Mechanistically, RANK-RANKL protects gut epithelial cells from cell death and controls the intestinal stem cell niche through BMP receptor signalling, resulting in the elongation of villi and a prominent increase in the intestinal surface. As a transgenerational consequence, babies born to female mice that lack Rank in the intestinal epithelium show reduced weight and develop glucose intolerance after metabolic stress. Whereas gut epithelial remodelling in pregnancy/lactation is reversible, constitutive expression of an active form of RANK is sufficient to drive intestinal expansion followed by loss of villi and stem cells, and prevents the formation of Apcmin-driven small intestinal stem cell tumours. These data identify RANK-RANKL as a pathway that drives intestinal epithelial expansion in pregnancy/lactation, one of the most elusive and fundamental tissue remodelling events in mammalian life history and evolution.

An inhibitory segment within G-patch activators tunes Prp43-ATPase activity during ribosome assembly

Mechanisms by which G-patch activators tune the processive multi-tasking ATP-dependent RNA helicase Prp43 (DHX15 in humans) to productively remodel diverse RNA:protein complexes remain elusive. Here, a comparative study between a herein and previously characterized activators, Tma23 and Pxr1, respectively, defines segments that organize Prp43 function during ribosome assembly. In addition to the activating G-patch, we discover an inhibitory segment within Tma23 and Pxr1, I-patch, that restrains Prp43 ATPase activity. Cryo-electron microscopy and hydrogen-deuterium exchange mass spectrometry show how I-patch binds to the catalytic RecA-like domains to allosterically inhibit Prp43 ATPase activity. Tma23 and Pxr1 contain dimerization segments that organize Prp43 into higher-order complexes. We posit that Prp43 function at discrete locations on pre-ribosomal RNA is coordinated through toggling interactions with G-patch and I-patch segments. This could guarantee measured and timely Prp43 activation, enabling precise control over multiple RNA remodelling events occurring concurrently during ribosome formation.

Role of NLRP3 Inflammasome in Heart Failure Patients Undergoing Cardiac Surgery as a Potential Determinant of Postoperative Atrial Fibrillation and Remodeling: Is SGLT2 Cotransporter Inhibition an Alternative for Cardioprotection?

In heart failure (HF) patients undergoing cardiac surgery, an increased activity of mechanisms related to cardiac remodeling may determine a higher risk of postoperative atrial fibrillation (POAF). Given that atrial fibrillation (AF) has a negative impact on the course and management of HF, including the need for anticoagulation therapy, identifying the factors associated with AF occurrence after cardiac surgery is crucial for the prognosis of these patients. POAF is thought to occur when various clinical and biochemical triggers act on susceptible cardiac tissue (first hit), with oxidative stress and inflammation during cardiopulmonary bypass (CPB) surgery being potential contributing factors (second hit). However, the molecular mechanisms involved in these processes remain poorly characterized. Recent research has shown that patients who later develop POAF often have pre-existing abnormalities in calcium handling and activation of NLRP3-inflammasome signaling in their atrial cardiomyocytes. These molecular changes may make cardiomyocytes more susceptible to spontaneous Ca2+-releases and subsequent arrhythmias, particularly when exposed to inflammatory mediators. Additionally, some clinical studies have linked POAF with elevated preoperative inflammatory markers, but there is a need for further research in order to better understand the impact of CPB surgery on local and systemic inflammation. This knowledge would make it possible to determine whether patients susceptible to POAF have pre-existing inflammatory conditions or cellular electrophysiological factors that make them more prone to developing AF and cardiac remodeling. In this context, the NLRP3 inflammasome, expressed in cardiomyocytes and cardiac fibroblasts, has been identified as playing a key role in the development of HF and AF, making patients with pre-existing HF with reduced ejection fraction (HFrEF) the focus of several clinical studies with interventions that act at this level. On the other hand, HFpEF has been linked to metabolic and non-ischemic risk factors, but more research is needed to better characterize the myocardial remodeling events associated with HFpEF. Therefore, since ventricular remodeling may differ between HFrEF and HFpEF, it is necessary to perform studies in both groups of patients due to their pathophysiological variations. Clinical evidence has shown that pharmacological therapies that are effective for HFrEF may not provide the same anti-remodeling benefits in HFpEF patients, particularly compared to traditional adrenergic and renin-angiotensin-aldosterone system inhibitors. On the other hand, there is growing interest in medications with pleiotropic or antioxidant/anti-inflammatory effects, such as sodium-glucose cotransporter 2 inhibitors (SGLT-2is). These drugs may offer anti-remodeling effects in both HFrEF and HFpEF by inhibiting pro-inflammatory, pro-oxidant, and NLRP3 signaling pathways and their mediators. The anti-inflammatory, antioxidant, and anti-remodeling effects of SGLT-2 i have progressively expanded from HFrEF and HFpEF to other forms of cardiac remodeling. However, these advances in research have not yet encompassed POAF despite its associations with inflammation, oxidative stress, and remodeling. Currently, the direct or indirect effects of NLRP3-dependent pathway inhibition on the occurrence of POAF have not been clinically assessed. However, given that NLRP3 pathway inhibition may also indirectly affect other pathways, such as inhibition of NF-kappaB or inhibition of matrix synthesis, which are strongly linked to POAF and cardiac remodeling, it is reasonable to hypothesize that this type of intervention could play a role in preventing these events.

Abstract 4132838: Coronary Collaterals Provide Cardioprotection in Hemorrhagic ST-elevation MI (STEMI)

Introduction: Development of intramyocardial hemorrhage (IMH) in acute STEMI following reperfusion is estimated to affect 35-50% of patients. IMH is a lethal event as it contributes to larger MI size, compromised myocardial salvage, adverse left ventricular (LV) remodeling, lower LVEF, and consequential major adverse CV events post-MI. Whether coronary collateral circulation reduces the deleterious effects of IMH has not been investigated. Hypothesis: We hypothesized that coronary collaterals could reduce the extent of post-reperfusion IMH volume and offer cardioprotection to hemorrhagic MI patients. Methods: MIRON-CL (NCT05898425) recruited and studied STEMI patients (n=294) reperfused via PCI. Pre-PCI coronary angiography allowed for assessment of collateral vessels using the Rentrop grading system, from Grade 0 (no collaterals) to Grade III (complete collateral filling). Post-PCI cardiac MRI, performed 3 days later, was used to determine area affected (extent of myocardial edema) from T2 maps, extent of IMH from T2* maps and MI size from LGE as %LV. Statistical analyses were used to examine relationships between collateral grades, MI size, IMH, and area affected. Results: 124 patients were hemorrhagic and 170 were non-hemorrhagic. Patients with no collaterals (Grade 0; CL-) exhibited significantly higher IMH volumes (7.41 ± 5.33% LV) compared to those with collaterals (Grade I: 5.23 ± 3.21% LV, Grade II: 3.11 ± 2.78% LV, Grade III: 2.05 ± 1.89% LV; p<0.001). Total area affected post-PCI was larger in CL- (37.62 ± 15.32% LV) compared to CL+ (21.48 ± 13.21% LV, p<0.001). Presence of collateral circulation (Grade>0 combined; CL+) was correlated with smaller MI sizes (CL-: 38.66 ± 14.63% LV vs. CL+: 19.84 ± 13.72% LV, p<0.001) and reduced MVO volumes (CL-: 8.07 ± 6.60% LV vs. CL+: 2.17 ± 2.35% LV, p<0.001). Patients with no collaterals had a significantly higher adj. risk of IMH (OR: 5.71, 95% CI: 3.16-10.33, p<0.0001). Conclusion: Coronary collaterals reduce post-reperfusion IMH volume in STEMI patients and provide significant cardioprotection: reductions in area affected, MVO and MI size. Insight into collateral grade offers opportunities to improve risk stratification and management of revascularized STEMI patients.

Dynamic evolution of fibroblasts revealed by single cell RNA sequencing of human pancreatic cancer.

Cancer progression and response to therapy are inextricably reliant on the co-evolution of a supportive tissue microenvironment. This is particularly evident in pancreatic ductal adenocarcinoma (PDAC), a tumor type characterized by expansive and heterogeneous stroma. Herein, we employed single cell RNAseq and spatial transcriptomics of normal, inflamed, and malignant pancreatic tissues to contextualize stromal dynamics associated with disease and treatment status, identifying temporal and spatial trajectories of fibroblast differentiation. Using analytical tools to infer cellular communication, together with a newly developed assay to annotate genomic alterations in cancer cells, we additionally explored the complex intercellular networks underlying tissue circuitry, highlighting a fibroblast-centric interactome that grows in strength and complexity in the context of malignant transformation. Our study yields new insights on the stromal remodeling events favoring the development of a tumor-supportive microenvironment and provides a powerful resource for the exploration of novel points of therapeutic intervention in PDAC.

Long-term prognostic value of microvascular obstruction by cardiac magnetic resonance in ST-segment elevation myocardial infarction

Abstract Background Microvascular obstruction (MVO) has been associated with a higher risk of cardiac remodelling and adverse events following ST-segment elevation myocardial infarction (STEMI). However, long-term prognostic implications of MVO in STEMI beyond five years of follow-up have not been assessed to date. Purpose To investigate the relation of MVO with all-cause mortality and recurrent ischemic events at long-term follow-up after STEMI. Methods This is a pooled analysis of three observational studies including 876 prospectively enrolled reperfused first STEMI patients, who underwent cardiac magnetic resonance imaging with late gadolinium enhancement, between 2003-2019, from four university medical centers in the Netherlands and Spain. Median follow-up duration was 6.3 (IQR 3.6-9.3) years. The primary outcome was all-cause mortality. The secondary outcome was a combined endpoint of all-cause mortality and recurrent ischemic events (i.e. myocardial infarction or stroke). We performed Cox regression analyses with a time-dependent covariate. Model 1 included correction for clinical covariates only, i.e. age, sex, smoking, diabetes mellitus, hypertension, and LAD culprit artery. Model 2 included imaging characteristics, i.e. infarct size and left ventricular ejection fraction, in addition to the clinical covariates. Results The study population consisted of 876 patients, mean age 59 years ± 12, 720 men (82%). MVO was present in 499 patients (58%). The presence of MVO was significantly associated with all-cause mortality up to six years post-STEMI, independent from clinical characteristics (Hazard Ratio [HR] 2.23, 95% CI 1.09-4.57, p=0.029), but not after six years post-STEMI (HR 0.98, 95% CI 0.45-2.12, p=0.958). Presence of MVO was not significantly associated with a combined endpoint of all-cause mortality and recurrent ischemic events before or after six years of follow-up (HR 1.27, 95% CI 0.81-1.99, p=0.294 and HR 0.68, 95% CI 0.35-1.31, p=0.244, respectively). All other traditional prognosticators, except age, also lacked predictive value at long-term follow-up beyond six years. Conclusions In STEMI patients, the presence of MVO by cardiac magnetic resonance imaging is associated with a more than two-fold higher risk of all-cause mortality up to six years after the index event. This relation seems to dissipate beyond this time period. Furthermore, presence of MVO was not associated with recurrent ischemic events at long-term follow-up post-STEMI.

Ca2+-dependent vesicular and non-vesicular lipid transfer controls hypoosmotic plasma membrane expansion.

Robust coordination of surface and volume changes is critical for cell integrity. Few studies have elucidated the plasma membrane (PM) remodeling events during cell surface and volume alteration, especially regarding PM sensing and its subsequent rearrangements. Here, using fission yeast protoplasts, we reveal a Ca2+-dependent mechanism for membrane addition that ensures PM integrity and allows its expansion during acute hypoosmotic cell swelling. We show that MscS-like mechanosensitive channels activated by PM tension control extracellular Ca2+ influx, which triggers direct lipid transfer at endoplasmic reticulum (ER)-PM contact sites by conserved extended-synaptotagmins and accelerates exocytosis, enabling PM expansion necessary for osmotic equilibrium. Defects in any of these key events result in rapid protoplast rupture upon severe hypotonic shock. Our numerical simulations of hypoosmotic expansion further propose a cellular strategy that combines instantaneous non-vesicular lipid transfer with bulk exocytic membrane delivery to maintain PM integrity for dramatic cell surface/volume adaptation.

DivIVA controls the dynamics of septum splitting and cell elongation in Streptococcus pneumoniae.

Bacterial shape and division rely on the dynamics of cell wall assembly, which involves regulated synthesis and cleavage of the peptidoglycan. In ovococci, these processes are coordinated within an annular mid-cell region with nanometric dimensions. More precisely, the cross-wall synthesized by the divisome is split to generate a lateral wall, whose expansion is insured by the insertion of the so-called peripheral peptidoglycan by the elongasome. Septum cleavage and peripheral peptidoglycan synthesis are, thus, crucial remodeling events for ovococcal cell division and elongation. The structural DivIVA protein has long been known as a major regulator of these processes, but its mode of action remains unknown. Here, we integrate click chemistry-based peptidoglycan labeling, direct stochastic optical reconstruction microscopy, and in silico modeling, as well as epifluorescence and stimulated emission depletion microscopy to investigate the role of DivIVA in Streptococcus pneumoniae cell morphogenesis. Our work reveals two distinct phases of peptidoglycan remodeling during the cell cycle that are differentially controlled by DivIVA. In particular, we show that DivIVA ensures homogeneous septum cleavage and peripheral peptidoglycan synthesis around the division site and their maintenance throughout the cell cycle. Our data additionally suggest that DivIVA impacts the contribution of the elongasome and class A penicillin-binding proteins to cell elongation. We also report the position of DivIVA on either side of the septum, consistent with its known affinity for negatively curved membranes. Finally, we take the opportunity provided by these new observations to propose hypotheses for the mechanism of action of this key morphogenetic protein.IMPORTANCEThis study sheds light on fundamental processes governing bacterial growth and division, using integrated click chemistry, advanced microscopy, and computational modeling approaches. It addresses cell wall synthesis mechanisms in the opportunistic human pathogen Streptococcus pneumoniae, responsible for a range of illnesses (otitis, pneumonia, meningitis, septicemia) and for one million deaths every year worldwide. This bacterium belongs to the morphological group of ovococci, which includes many streptococcal and enterococcal pathogens. In this study, we have dissected the function of DivIVA, which is a structural protein involved in cell division, morphogenesis, and chromosome partitioning in Gram-positive bacteria. This work unveils the role of DivIVA in the orchestration of cell division and elongation along the pneumococcal cell cycle. It not only enhances our understanding of how ovoid bacteria proliferate but also offers the opportunity to consider how DivIVA might serve as a scaffold and sensor for particular membrane regions, thereby participating in various cell cycle processes.

Myocardial ischemia in patients with mild-to-moderate aortic stenosis: Interaction with cardiac remodeling and adverse events

BackgroundThe association between aortic valve stenosis (AVS) and myocardial perfusion abnormalities has been incompletely characterized. We sought to assess the predictors of myocardial ischemia in patients with mild-to-moderate AVS, and its relationship with long-term prognosis. MethodsEighty-nine patients with mild-to-moderate AVS (peak velocity between 2.6 and 4.0 m/second and aortic valve area > .6 cm2/m2), preserved left ventricular (LV) function, and either normal coronary arteries (28 patients) or non-obstructive coronary artery disease (<50% stenosis; 61 patients) were individuated. Myocardial perfusion imaging was performed using a cadmium–zinc–telluride camera, and the summed difference score (SDS) was computed. The presence of either LV hypertrophy (LVH) (LV mass index [LVMI] > 115 g/m2 [males] or 95 g/m2 [females]) or concentric LV remodeling (relative wall thickness: >.42) was determined at two-dimensional echocardiography. ResultsForty (45%) and 49 (55%) patients had mild and moderate AVS, respectively. Fifty (56%), 17 (19%), and 22 (25%) patients had normal LV geometry, concentric LV remodeling, and LVH, respectively. An interaction between LV remodeling and inducible ischemia was revealed with progressively higher values of SDS in patients with normal LV geometry (3 ± 3), concentric remodeling (4 ± 2), and LVH (7 ± 2) (P < .001).Accordingly, a moderate correlation existed between LVMI and SDS values (R: .67; P < .001). After a median follow-up of 84 ± 47 months, 27 adverse events were recorded, including 19 AV replacements and 8 deaths. On multivariable analysis, the presence of LVH (hazard ratio [HR]: 6.46; 95% confidence interval [CI]: 2.09–20.00; P = .001) and a higher SDS (HR: 1.41; 95% CI: 1.15–1.75; P = .001) were the two independent predictors of AE. ConclusionsIn patients with mild-to-moderate AVS, myocardial ischemia correlates with the severity of adverse LV remodeling. Patients with LVH and ischemia are at increased risk of AE.

Dissecting contributions of pulmonary arterial remodeling to right ventricular afterload in pulmonary hypertension.

Pulmonary hypertension (PH) is defined as an elevation in the right ventricle (RV) afterload, characterized by increased hemodynamic pressure in the main pulmonary artery (PA). Elevations in RV afterload increase RV wall stress, resulting in RV remodeling and potentially RV failure. From a biomechanical standpoint, the primary drivers for RV afterload elevations include increases in pulmonary vascular resistance (PVR) in the distal vasculature and decreases in vessel compliance in the proximal PA. However, the individual contributions of the various vascular remodeling events toward the progression of PA pressure elevations and altered vascular hemodynamics remain elusive. In this study, we used a subject-specific one-dimensional (1D) fluid-structure interaction (FSI) model to investigate the alteration of pulmonary hemodynamics in PH and to quantify the contributions of vascular stiffening and increased resistance towards increased main pulmonary artery (MPA) pressure. We used a combination of subject-specific hemodynamic measurements, ex-vivo mechanical testing of arterial tissue specimens, and ex-vivo X-ray micro-tomography imaging to develop the 1D-FSI model and dissect the contribution of PA remodeling events towards alterations in the MPA pressure waveform. Both the amplitude and pulsatility of the MPA pressure waveform were analyzed. Our results indicated that increased distal resistance has the greatest effect on the increase in maximum MPA pressure, while increased stiffness caused significant elevations in the characteristic impedance. The method presented in this study will serve as an essential step toward understanding the complex interplay between PA remodeling events that leads to the most severe adverse effect on RV dysfunction.

Genotype is associated with left ventricular reverse remodelling and early events in recent-onset dilated cardiomyopathy.

Recent-onset dilated cardiomyopathy (RODCM) is characterized by heterogeneous aetiology and diverse clinical outcomes, with scarce data on genotype-phenotype correlates. Our aim was to correlate individual RODCM genotypes with left ventricular reverse remodelling (LVRR) and clinical outcomes. In this prospective study, a total of 386 Czech RODCM patients with symptom duration ≤6months underwent genetic counselling and whole-exome sequencing (WES). The presence of pathogenic (class 5) or likely pathogenic (class 4) variants in a set of 72 cardiomyopathy-related genes was correlated with the occurrence of all-cause death, heart transplantation, or implantation of a ventricular assist device (primary outcome) and/or ventricular arrhythmia event (secondary outcome). LVRR was defined as an improvement of left ventricular ejection fraction to >50% or ≥10% absolute increase, with a left ventricular end-diastolic diameter ≤33mm/m2 or ≥10% relative decrease. Median follow-up was 41months. RODCM was familial in 98 (25%) individuals. Class 4-5 variants of interest (VOIs) were identified in 125 (32%) cases, with 69 (18%) having a single titin-truncating variant (TTNtv) and 56 (14%) having non-titin (non-TTN) VOIs. The presence of class 4-5 non-TTN VOIs, but not of TTNtv, heralded a lower probability of 12-month LVRR and proved to be an independent baseline predictor both of the primary and the secondary outcome. The negative result of genetic testing was a strong protective baseline variable against occurrence of life-threatening ventricular arrhythmias. Detection of class 4-5 VOIs in genes coding nuclear envelope proteins was another independent predictor of both study outcomes at baseline and also of life-threatening ventricular arrhythmias after 12months. Class 4-5 VOIs of genes coding cytoskeleton were associated with an increased risk of life-threatening ventricular arrhythmias after baseline assessment. A positive family history of dilated cardiomyopathy alone only related to a lower probability of LVRR at 12months and at the final follow-up. RODCM patients harbouring class 4-5 non-TTN VOIs are at higher risk of progressive heart failure and life-threatening ventricular arrhythmias. Genotyping may improve their early risk stratification at baseline assessment.

Abstract Mo024: Integrated analysis of ex vivo biomechanical ventricular remodeling and imaging-based in vivo strain changes in a pre-clinical murine model of radiation-induced cardiotoxicity

Introduction: Thoracic radiation therapy (RT) is commonly used for the treatment of many common malignancies, such as lung and breast cancer, but carries a high risk of radiation-induced cardiotoxicity (RIC). Existing diagnosis of RIC is challenged by subclinical ventricular dysfunction, not captured by global indices of cardiac function. Understanding RIC-driven biomechanical remodeling of the myocardium will provide novel insights into developing high-fidelity imaging approaches for early detection of RIC. Methods: A pre-clinical model of RIC was developed by administering whole heart irradiation under image guidance in mice (8 Gy x 5) over five consecutive days. A longitudinal study was carried out to investigate the biomechanical response of the left ventricle (LV). Cardiac magnetic resonance imaging was performed to estimate end-systolic strains. Mechanical testing was performed on the harvested LV free wall (LVFW) specimens to measure passive stiffness, calculated as the tangent to the ensemble stress-strain curve at 30% strain. Results: A significant increase in passive LVFW stiffness was observed at 3M post-RT (Figs. 1A and B). Significant declines in both global circumferential strain (GCS) and global radial strain (GRS) at 3M post-RT, compared to respective measurements at pre-RT, were observed (Figs. 1C and D). Suppressed contractile strains suggested biomechanical remodeling of the LV, including impaired contractility and passive stiffening of the LVFW, consistent with ex-vivo measurements. Conclusion: We have established a direct correlation between ex-vivo mechanical testing (elevated stiffness) and reduced contractile strains in in-vivo analysis in a mouse model of RIC. Such integrated analysis will pave the way towards developing highly sensitive imaging approaches that non-invasively recapitulate the ventricular remodeling events associated with RIC, thereby enabling early detection of RIC in patients receiving thoracic RT.

Comprehensive Characterization of Islet Remodeling in Development and in Diabetes Using Mass Cytometry.

The pancreatic islet is the functional and structural unit of the pancreatic endocrine portion. Islet remodeling occurs in both normal development and pathogenesis of type 1 (T1D) and type 2 diabetes (T2D). However, accurately quantifying changes in islet cellular makeup and hormone expressions poses significant challenges due to large intra- and inter-donor heterogeneity and the limited scalability of traditional methods such as immunostaining. The cytometry by time-of-flight (CyTOF) technology enables simultaneous quantification of more than 30 protein markers at single-cell resolution in a high-throughput fashion. Moreover, with distinct DNA and viability markers, single live cells can be explicitly selected in CyTOF. Here, leveraging the CyTOF data generated by the Human Pancreas Analysis Program, we characterized more than 12 million islet cells from 71 donors. Our data revealed continued age-related changes in islet endocrine cell compositions, but the maturity of endocrine cells is reached by 3 years of age. We also observed significant changes in beta cell numbers and key protein expressions, along with a significant increase in bihormonal cells in T1D donors. In contrast, T2D donors exhibited minimal islet remodeling events. Our data shine a light on the islet dynamics during development and diabetes pathogenesis and suggest divergent pathogenesis processes of T1D and T2D. Our comprehensive approach not only elucidates islet plasticity but also establishes a foundation for integrated CyTOF analysis in islet biology and beyond.

Tetraspanin proteins in membrane remodeling processes.

Membrane remodeling is a fundamental cellular process that is crucial for physiological functions such as signaling, membrane fusion and cell migration. Tetraspanins (TSPANs) are transmembrane proteins of central importance to membrane remodeling events. During these events, TSPANs are known to interact with themselves and other proteins and lipids; however, their mechanism of action in controlling membrane dynamics is not fully understood. Since these proteins span the membrane, membrane properties such as rigidity, curvature and tension can influence their behavior. In this Review, we summarize recent studies that explore the roles of TSPANs in membrane remodeling processes and highlight the unique structural features of TSPANs that mediate their interactions and localization. Further, we emphasize the influence of membrane curvature on TSPAN distribution and membrane domain formation and describe how these behaviors affect cellular functions. This Review provides a comprehensive perspective on the multifaceted function of TSPANs in membrane remodeling processes and can help readers to understand the intricate molecular mechanisms that govern cellular membrane dynamics.

Osteoclast-derived coupling factors: origins and state-of-play Louis V Avioli lecture, ASBMR 2023.

Coupling, the mechanism that controls the sequence of events in bone remodeling, is a fundamental theory for understanding the way the skeleton changes throughout life. This review is an adapted version of the Louis V Avioli lecture, delivered at the Annual Scientific Meeting of the American Society of Bone and Mineral Research in 2023. It outlines the history of the coupling concept, details how coupling is thought to occur within trabecular and cortical bone, and describes its multiple contexts and the many mechanisms suggested to couple bone-forming osteoblasts to the prior action of osteoclasts on the same bone surface. These mechanisms include signals produced at each stage of the remodeling sequence (resorption, reversal, and formation), such as factors released by osteoclasts through their resorptive action and through protein synthesis, molecules deposited in the cement line during the reversal phase, and potential signals from osteocytes within the local bone environment. The review highlights two examples of coupling factors (Cardiotrophin 1 and EphrinB2:EphB4) to illustrate the limited data available, the need to integrate the many functions of these factors within the basic multicellular unit (BMU), and the multiple origins of these factors, including the other cell types present during the remodeling sequence (such as osteocytes, macrophages, endothelial cells, and T-cells).

LV cathode position in CRT recipients: How can we benefit from CMR?

BackgroundLeft ventricular lead positioning represents a key step in CRT optimization. However, evidence for its guidance based on specific topographical factors and related imaging techniques is sparse. ObjectiveTo analyze reverse remodeling (RR) and clinical events in CRT recipients based on LV cathode (LVC) position relative to latest mechanical activation (LMA) and scar as determined by cardiac magnetic resonance (CMR). MethodsThis is a retrospective single-center study of 68 consecutive Q-LV-guided CRT-D and CRT-P recipients. Through CMR-based 3D reconstructions overlayed on fluoroscopy images, LVCs were stratified as concordant, adjacent, or discordant to LMA (3 segments with latest and greatest radial strain) and scar (segments with >50% scar transmurality). The primary endpoint of RR (expressed as percentage ESV change) and secondary composite endpoint of HF hospitalizations, LVAD/heart transplant, or cardiovascular death were compared across categories. ResultsLVC proximity to LMA was associated with a progressive increase in RR (percentage ESV change: concordant −47.0 ± 5.9%, adjacent −31.4 ± 3.1%, discordant +0.4 ± 3.7%), while proximity to scar was associated with sharply decreasing RR (concordant +10.7 ± 12.9%, adjacent +0.3 ± 5.3%, discordant −31.3 ± 4.4%, no scar −35.4 ± 4.8%). 4 integrated classes of LVC position demonstrated a significant positive RR gradient the more optimal the category (class I -47.0 ± 5.9%, class II -34.9 ± 2.8%, class III -5.5 ± 4.3%, class IV + 3.4 ± 5.2%). Freedom from composite secondary endpoint of HF hospitalization, LVAD/heart transplant, or cardiovascular death confirmed these trends demonstrating significant differences across both integrated as well as individual LMA and scar categories. ConclusionIntegrated CMR-determined LVC position relative to LMA and scar stratifies response to CRT.

Left ventricular geometry characteristics and clinical outcomes in hemodialysis patients with heart failure with preserved ejection fraction

BackgroundThe relationships among left heart remodeling, cardiac function, and cardiovascular events (CEs) in patients with heart failure (HF) with preserved ejection fraction (HFpEF) undergoing maintenance hemodialysis (MHD) remain unclear. We evaluated the echocardiographic characteristics and clinical outcomes of such patients with diverse left ventricular geometric (LVG) configurations.MethodsOverall, 210 patients with HFpEF undergoing MHD (cases) and 60 healthy controls were enrolled. Cases were divided into four subgroups based on LVG and were followed up for three years. The primary outcomes were the first CEs and all-cause mortality.ResultsLeft ventricular ejection fraction (LVEF) and right ventricular systolic function did significantly differ between cases and controls, whereas echocardiographic parameters of cardiac structure, diastolic function, and left ventricular global longitudinal strain (LVGLS) differed significantly. The proportion of cases with left ventricular hypertrophy (LVH) was 67.1%. In addition, 2.38%, 21.90%, 12.86%, and 62.86% of cases presented with normal geometry (NG), concentric remodeling (CR), eccentric hypertrophy (EH), and concentric hypertrophy (CH), respectively. The left atrial diameter (LAD) was the largest and cardiac output index was the lowest in the EH subgroup. The score of Acute Dialysis Quality Initiative Workgroup (ADQI) HF class was worse in the EH subgroup than in other subgroups at baseline. The proportions of cases free of adverse CEs in the EH subgroup at 12, 24, and 36 months were 40.2%, 14.8%, and 0%, respectively, and the survival rates were 85.2%, 29.6%, 3.7%, respectively, which were significantly lower than those in other subgroups. Multivariate Cox regression revealed that age, TNI (Troponin I), EH, left ventricular mass index (LVMI), age and EH configuration were independent risk factors for adverse CEs and all-cause mortality in the cases.ConclusionMost patients with HFpEF receiving MHD have LVH and diastolic dysfunction. Among the four LVGs, patients with HFpEF undergoing MHD who exhibited EH had the highest risk of adverse CEs and all-cause mortality.

Impact of non-typical LBBB on CRT response

Abstract Introduction Cardiac resynchronization therapy (CRT) benefits have been established in patients with heart failure and reduced left ventricular ejection fraction (HFrEF) who have a broad QRS and remain symptomatic despite optimized medical therapy. Responders typically are female, with LBBB and broader QRS. It remains uncertain to what extent do patients with non-LBBB QRS complex morphology respond to CRT and also if there are differences among various types of intraventricular conduction delays. Purpose To evaluate the impact of non-typical left bundle branch block (LBBB) on reverser remodeling and clinical events. Methods Single center, observational, retrospective study including patients (pts) who implanted CRT in the context of HFrEF, from 2015 to 2020. Evaluation of QRS morphology analysis was conducted. CRT response was defined by a reduction of LVESV≥15% or an increase in LVEF≥10%. Predictors of CRT response were evaluated with Chi-square and Mann- Whitney analysis. Impact on reverse remodeling and clinical outcomes was performed with Kaplan-Meyer analysis. Results A total of 361 pts were included for analysis, of which 184 had non-typical LBBB. Pts had a mean age of 71±9years old, the majority of pts were female (61%), and almost half were ischemic (47.8%). EGC evaluation prior to CRT implantation, revealed an atypical LBBB in 83 (45.1%) pts, typical RBBB in 23 (12.5%) pts, atypical RBBB 94.(9%) pts and nonspecific intraventricular conduction delay in 69 (37.5%) pts. During a mean time of follow-up of 2.9 ±2.4years, 33 pts (18%) had hospitalizations due to HF and 68 (37%) died. In this cohort, 78 pts (42.4%) were deemed as responders, who presented a better clinical outcome when compared to non-responders (p &amp;lt; 0.001, HR 2.629 [95% CI 1.635-4.225]. There was no difference among the four types of intraventricular conduction analyzed in respect to degree of CRT response – figure 1. Regarding clinical events during follow-up, there was once again no significant difference among the different patterns of non-typical LBBB– figure 2. In this subset population we found no independent predictors of CRT response, although non-responders were significantly older than responders (72±8 vs 69±10 years-old (p=0.016). Conclusion Although pts with non-typical LBBB morphology display a lower therapy response to CRT than reported for LBBB pts, the rate of response is not negligible and represents a protective factor for clinical outcomes. Different types of intraventricular conduction delay present no difference regarding long- term prognosis or reverse remodeling.Survival according to CRT response