Alternating high-fat diet enhances atherosclerosis by neutrophil reprogramming.

Systemic immune responses caused by chronic hypercholesterolaemia contribute to atherosclerosis initiation, progression and complications1. However, individuals often change their dietary habits over time2, and the effects of an alternating high-fat diet (HFD) on atherosclerosis remain unclear. Here, to address this relevant issue, we developed a protocol using atherosclerosis-prone mice to compare an alternating versus continuous HFD while maintaining similar overall exposure periods. We found that an alternating HFD accelerated atherosclerosis in Ldlr-/- and Apoe-/- mice compared with a continuous HFD. This pro-atherogenic effect of the alternating HFD was also observed in Apoe-/-Rag2-/- mice lacking T, B and natural killer T cells, ruling out the role of the adaptive immune system in the observed phenotype. Discontinuing the HFD in the alternating HFD group downregulated RUNX13, promoting inflammatory signalling in bone marrow myeloid progenitors. After re-exposure to an HFD, these cells produced IL-1ß, leading to emergency myelopoiesis and increased neutrophil levels in blood. Neutrophils infiltrated plaques and released neutrophil extracellular traps, exacerbating atherosclerosis. Specific depletion of neutrophils or inhibition of IL-1ß pathways abolished emergency myelopoiesis and reversed the pro-atherogenic effects of the alternating HFD. This study highlights the role of IL-1ß-dependent neutrophil progenitor reprogramming in accelerated atherosclerosis induced by alternating HFD.

The unreasonable effectiveness of equilibrium gene regulation through the cell cycle.

Systems like the prototypical lac operon can reliably hold repression of transcription upon DNA replication across cell cycles with just 10 repressor molecules per cell and behave as if they were at equilibrium. The origin of this phenomenology is still an unresolved question. Here, we develop a general theory to analyze strong perturbations in quasi-equilibrium systems and use it to quantify the effects of DNA replication in gene regulation. We find a scaling law linking actual with predicted equilibrium transcription via a single kinetic parameter. We show that even the lac operon functions beyond the physical limits of naive regulation through compensatory mechanisms that suppress non-equilibrium effects. Synthetic systems without adjuvant activators, such as the cAMP receptor protein (CRP), lack this reliability. Our results provide a rationale for the function of CRP, beyond just being a tunable activator, as a mitigator of cell cycle perturbations.

Harnessing intestinal tryptophan catabolism to relieve atherosclerosis in mice.

Tryptophan (Trp) is an essential amino acid, whose metabolism is a key gatekeeper of intestinal homeostasis. Yet, its systemic effects, particularly on atherosclerosis, remain unknown. Here we show that high-fat diet (HFD) increases the activity of intestinal indoleamine 2, 3-dioxygenase 1 (IDO), which shifts Trp metabolism from the production of microbiota-derived indole metabolites towards kynurenine production. Under HFD, the specific deletion of IDO in intestinal epithelial cells leads to intestinal inflammation, impaired intestinal barrier, augmented lesional T lymphocytes and atherosclerosis. This is associated with an increase in serotonin production and a decrease in indole metabolites, thus hijacking Trp for the serotonin pathway. Inhibition of intestinal serotonin production or supplementation with indole derivatives alleviates plaque inflammation and atherosclerosis. In summary, we uncover a pivotal role of intestinal IDO in the fine-tuning of Trp metabolism with systemic effects on atherosclerosis, paving the way for new therapeutic strategies to relieve gut-associated inflammatory diseases.

Dynamic and Postural Changes in Forelimb Amputee Dogs: A Pilot Study.

The amputation of a limb in quadrupeds can overload the remaining limbs, especially the contralateral one. The compensatory effort is especially high if it is a forelimb. It is, therefore, important to objectively know the changes in weight redistribution that occur in the animal while walking and standing still. With this objective, static (postural) and dynamic kinetic examinations were carried out on five French bulldogs with an amputated forelimb and five intact French bulldogs. For this examination, force and pressure platforms were used. The results were statistically compared using the student t-test. The parameters derived from the ground reaction forces were significantly higher in the amputee group. Surprisingly, postural examination showed that amputated dogs reached the same stability as healthy ones. Tripedal support in dogs does not objectively imply a loss of balance in quantitative terms; although the increase in force used by the remaining limb, as well as its altered cranial disposition during the support phase, may potentially predispose the animal to additional injuries in the future due to an overuse of different musculoskeletal units.

Multiparametric Comparison of Two TTA-Based Surgical Techniques in Dogs with Cranial Cruciate Ligament Tears.

Tearing of the cranial cruciate ligament causes hindlimb lameness in dogs. Different surgical procedures have been proposed to treat this condition. In this study, two different TTA-based techniques and implants were compared. A total of 30 dogs were separated into two groups according to the technique and implant used (Porous TTA® or Model Xgen®). The aim of the study was to assess whether one of these techniques has better functional recovery of the joint, better bone consolidation after the osteotomy procedure and fewer osteoarthritic changes. We compared both groups up to 3 months after surgery. No significant differences were found in any of the assessed parameters. Thus, both procedures were found to be equally effective and safe.

Dynamics-informed deconvolutional neural networks for super-resolution identification of regime changes in epidemiological time series.

The ability to infer the timing and amplitude of perturbations in epidemiological systems from their stochastically spread low-resolution outcomes is crucial for multiple applications. However, the general problem of connecting epidemiological curves with the underlying incidence lacks the highly effective methodology present in other inverse problems, such as super-resolution and dehazing from computer vision. Here, we develop an unsupervised physics-informed convolutional neural network approach in reverse to connect death records with incidence that allows the identification of regime changes at single-day resolution. Applied to COVID-19 data with proper regularization and model-selection criteria, the approach can identify the implementation and removal of lockdowns and other nonpharmaceutical interventions (NPIs) with 0.93-day accuracy over the time span of a year.

Multi-landmark alignment of genomic signals reveals conserved expression patterns across transcription start sites.

The prevalent one-dimensional alignment of genomic signals to a reference landmark is a cornerstone of current methods to study transcription and its DNA-dependent processes but it is prone to mask potential relations among multiple DNA elements. We developed a systematic approach to align genomic signals to multiple locations simultaneously by expanding the dimensionality of the genomic-coordinate space. We analyzed transcription in human and uncovered a complex dependence on the relative position of neighboring transcription start sites (TSSs) that is consistently conserved among cell types. The dependence ranges from enhancement to suppression of transcription depending on the relative distances to the TSSs, their intragenic position, and the transcriptional activity of the gene. Our results reveal a conserved hierarchy of alternative TSS usage within a previously unrecognized level of genomic organization and provide a general methodology to analyze complex functional relationships among multiple types of DNA elements.

Therapeutic potential of extracellular vesicles derived from cardiac progenitor cells in rodent models of chemotherapy-induced cardiomyopathy.

Background: Current treatments of chemotherapy-induced cardiomyopathy (CCM) are of limited efficacy. We assessed whether repeated intravenous injections of human extracellular vesicles from cardiac progenitor cells (EV-CPC) could represent a new therapeutic option and whether EV manufacturing according to a Good Manufacturing Practices (GMP)-compatible process did not impair their bioactivity. Methods: Immuno-competent mice received intra-peritoneal injections (IP) of doxorubicin (DOX) (4 mg/kg each; cumulative dose: 12 mg/kg) and were then intravenously (IV) injected three times with EV-CPC (total dose: 30 billion). Cardiac function was assessed 9-11 weeks later by cardiac magnetic resonance imaging (CMR) using strain as the primary end point. Then, immuno-competent rats received 5 IP injections of DOX (3 mg/kg each; cumulative dose 15 mg/kg) followed by 3 equal IV injections of GMP-EV (total dose: 100 billion). Cardiac function was assessed by two dimensional-echocardiography. Results: In the chronic mouse model of CCM, DOX + placebo-injected hearts incurred a significant decline in basal (global, epi- and endocardial) circumferential strain compared with sham DOX-untreated mice (p = 0.043, p = 0.042, p = 0.048 respectively) while EV-CPC preserved these indices. Global longitudinal strain followed a similar pattern. In the rat model, IV injections of GMP-EV also preserved left ventricular end-systolic and end-diastolic volumes compared with untreated controls. Conclusions: Intravenously-injected extracellular vesicles derived from CPC have cardio-protective effects which may make them an attractive user-friendly option for the treatment of CCM.

Acute stress induces long-term metabolic, functional, and structural remodeling of the heart.

Takotsubo cardiomyopathy is a stress-induced cardiovascular disease with symptoms comparable to those of an acute coronary syndrome but without coronary obstruction. Takotsubo was initially considered spontaneously reversible, but epidemiological studies revealed significant long-term morbidity and mortality, the reason for which is unknown. Here, we show in a female rodent model that a single pharmacological challenge creates a stress-induced cardiomyopathy similar to Takotsubo. The acute response involves changes in blood and tissue biomarkers and in cardiac in vivo imaging acquired with ultrasound, magnetic resonance and positron emission tomography. Longitudinal follow up using in vivo imaging, histochemistry, protein and proteomics analyses evidences a continued metabolic reprogramming of the heart towards metabolic malfunction, eventually leading to irreversible damage in cardiac function and structure. The results combat the supposed reversibility of Takotsubo, point to dysregulation of glucose metabolic pathways as a main cause of long-term cardiac disease and support early therapeutic management of Takotsubo.

Effect of the Thumb Orientation and Actuation on the Functionality and Performance of Affordable Prosthetic Hands: Obtaining Design Criteria.

The advent of 3D printing technologies has enabled the development of low-cost prosthetic underactuated hands, with cables working as tendons for flexion. Despite the particular relevance to human grasp, its conception in prosthetics is based on vague intuitions of the designers due to the lack of studies on its relevance to the functionality and performance of the device. In this work, some criteria for designers are provided regarding the carpometacarpal joint of the thumb in these devices. To this end, we studied four prosthetic hands of similar characteristics with the motion of abduction/adduction of the thumb resolved in three different ways: fixed at a certain abduction, coupled with the motion of flexion/extension, and actuated independently of the flexion/extension. The functionality and performance of the hands were assessed for the basic grasps using the Anthropomorphic Hand Assessment Protocol (AHAP) and a reduced version of the Southampton Hand Assessment Procedure (SHAP). As a general rule, it seems desirable that thumb adduction/abduction is performed independently of flexion/extension, although this adds one degree of control. If having this additional degree of control is beyond debate, coupled flexion/extension and adduction/abduction should be avoided in favour of the thumb having a fixed slight palmar abduction.

JAK2V617F mutation drives vascular resident macrophages toward a pathogenic phenotype and promotes dissecting aortic aneurysm.

JAK2V617F mutation is associated with an increased risk for athero-thrombotic cardiovascular disease, but its role in aortic disease development and complications remains unknown. In a cohort of patients with myeloproliferative neoplasm, JAK2V617F mutation was identified as an independent risk factor for dilation of both the ascending and descending thoracic aorta. Using single-cell RNA-seq, complementary genetically-modified mouse models, as well as pharmacological approaches, we found that JAK2V617F mutation was associated with a pathogenic pro-inflammatory phenotype of perivascular tissue-resident macrophages, which promoted deleterious aortic wall remodeling at early stages, and dissecting aneurysm through the recruitment of circulating monocytes at later stages. Finally, genetic manipulation of tissue-resident macrophages, or treatment with a Jak2 inhibitor, ruxolitinib, mitigated aortic wall inflammation and reduced aortic dilation and rupture. Overall, JAK2V617F mutation drives vascular resident macrophages toward a pathogenic phenotype and promotes dissecting aortic aneurysm.

Identification of Adipose Tissue as a Reservoir of Macrophages after Acute Myocardial Infarction.

Medullary and extra-medullary hematopoiesis has been shown to govern inflammatory cell infiltration and subsequently cardiac remodeling and function after acute myocardial infarction (MI). Emerging evidence positions adipose tissue (AT) as an alternative source of immune cell production. We, therefore, hypothesized that AT could act as a reservoir of inflammatory cells that participate in cardiac homeostasis after MI. To reveal the distinct role of inflammatory cells derived from AT or bone marrow (BM), chimeric mice were generated using standard repopulation assays. We showed that AMI increased the number of AT-derived macrophages in the cardiac tissue. These macrophages exhibit pro-inflammatory characteristics and their specific depletion improved cardiac function as well as decreased infarct size and interstitial fibrosis. We then reasoned that the alteration of AT-immune compartment in type 2 diabetes could, thus, contribute to defects in cardiac remodeling. However, in these conditions, myeloid cells recruited in the infarcted heart mainly originate from the BM, and AT was no longer used as a myeloid cell reservoir. Altogether, we showed here that a subpopulation of cardiac inflammatory macrophages emerges from myeloid cells of AT origin and plays a detrimental role in cardiac remodeling and function after MI. Diabetes abrogates the ability of AT-derived myeloid cells to populate the infarcted heart.

Robustness of DNA looping across multiple cell divisions in individual bacteria.

DNA looping has emerged as a central paradigm of transcriptional regulation, as it is shared across many living systems. One core property of DNA looping-based regulation is its ability to greatly enhance repression or activation of genes with only a few copies of transcriptional regulators. However, this property based on a small number of proteins raises the question of the robustness of such a mechanism with respect to the large intracellular perturbations taking place during growth and division of the cell. Here we address the issue of sensitivity to variations of intracellular parameters of gene regulation by DNA looping. We use the lac system as a prototype to experimentally identify the key features of the robustness of DNA looping in growing Escherichia coli cells. Surprisingly, we observe time intervals of tight repression spanning across division events, which can sometimes exceed 10 generations. Remarkably, the distribution of such long time intervals exhibits memoryless statistics that is mostly insensitive to repressor concentration, cell division events, and the number of distinct loops accessible to the system. By contrast, gene regulation becomes highly sensitive to these perturbations when DNA looping is absent. Using stochastic simulations, we propose that the observed robustness to division emerges from the competition between fast, multiple rebinding events of repressors and slow initiation rate of the RNA polymerase. We argue that fast rebinding events are a direct consequence of DNA looping that ensures robust gene repression across a range of intracellular perturbations.

Development of an Artificial Neural Network for the Detection of Supporting Hindlimb Lameness: A Pilot Study in Working Dogs.

Subjective lameness assessment has been a controversial subject given the lack of agreement between observers; this has prompted the development of kinetic and kinematic devices in order to obtain an objective evaluation of locomotor system in dogs. After proper training, neural networks are potentially capable of making a non-human diagnosis of canine lameness. The purpose of this study was to investigate whether artificial neural networks could be used to determine canine hindlimb lameness by computational means only. The outcome of this study could potentially assess the efficacy of certain treatments against diseases that cause lameness. With this aim, input data were obtained from an inertial sensor positioned on the rump. Data from dogs with unilateral hindlimb lameness and sound dogs were used to obtain differences between both groups at walk. The artificial neural network, after necessary adjustments, was integrated into a web management tool, and the preliminary results discriminating between lame and sound dogs are promising. The analysis of spatial data with artificial neural networks was summarized and developed into a web app that has proven to be a useful tool to discriminate between sound and lame dogs. Additionally, this environment allows veterinary clinicians to adequately follow the treatment of lame canine patients.

Splenic Marginal Zone B Lymphocytes Regulate Cardiac Remodeling After Acute Myocardial Infarction in Mice.

BACKGROUND: Mature B lymphocytes alter the recovery of cardiac function after acute myocardial infarction (MI) in mice. Follicular B cells and marginal zone B (MZB) cells are spatially distinct mature B-cell populations in the spleen, and they exert specific functional properties. microRNA-21 (miR21)/hypoxia-inducible factor-α (HIF-α)-related pathways have been shown to govern B-cell functions. OBJECTIVES: The goal of this study was to unravel the distinct role of MZB cells and that of endogenous activation of miR21/HIF-α signaling in MZB cells during post-ischemic injury. METHODS: Acute MI was induced in mice by permanent ligation of the left anterior descending coronary artery. Cardiac function and remodeling were assessed by using echocardiography and immunohistochemistry. To determine the specific role of MZB cells, the study used mice with B-cell lineage-specific conditional deletion of Notch signaling, which leads to selection deficiency of MZB cells. To evaluate the role of the HIF-1α isoform, mice were generated with MZB-cell lineage-specific conditional deletion of Hif1a. RESULTS: Acute MI prompted an miR21-dependent increase in HIF-1α, particularly in splenic MZB cells. MZB cell deficiency and MZB cell-specific deletion of miR21 or Hif1a improved cardiac function after acute MI. miR21/HIF-1α signaling in MZB cells was required for Toll-like receptor dependent expression of the monocyte chemoattractant protein CCL7, leading to increased mobilization of inflammatory monocytes to the ischemic myocardium and to adverse post-ischemic cardiac remodeling. CONCLUSIONS: This work reveals a novel function for the miR21/HIF-1α pathway in splenic MZB cells with potential major implications for the modulation of cardiac function after acute MI.

Ascertaining the initiation of epidemic resurgences: an application to the COVID-19 second surges in Europe and the Northeast United States.

Assessing a potential resurgence of an epidemic outbreak with certainty is as important as it is challenging. The low number of infectious individuals after a long regression, and the randomness associated with it, makes it difficult to ascertain whether the infectious population is growing or just fluctuating. We have developed an approach to compute confidence intervals for the switching time from decay to growth and to compute the corresponding multiple-location aggregated quantities over a region to increase the precision of the determination. We estimated the aggregate prevalence over time for Europe and the northeast United States to characterize the COVID-19 second surge in these regions during year 2020. We find a starting date as early as 3 July (95% confidence interval (CI): 1-6 July) for Europe and 19 August (95% CI: 16-23 August) for the northeast United States; subsequent infectious populations that, as of 31 December, have always increased or remained stagnant; and the resurgences being the collective effect of each overall region with no location, either country or state, dominating the regional dynamics by itself.

Extracellular vesicles fail to trigger the generation of new cardiomyocytes in chronically infarcted hearts.

Background: Extracellular vesicles (EV) mediate the therapeutic effects of stem cells but it is unclear whether this involves cardiac regeneration mediated by endogenous cardiomyocyte proliferation. Methods: Bi-transgenic MerCreMer/ZEG (n = 15/group) and Mosaic Analysis With Double Markers (MADM; n = 6/group) mouse models underwent permanent coronary artery ligation and received, 3 weeks later, 10 billion EV (from human iPS-derived cardiovascular progenitor cells [CPC]), or saline, injected percutaneously under echo guidance in the peri-infarcted myocardium. Endogenous cardiomyocyte proliferation was tracked by EdU labeling and biphoton microscopy. Other end points, including cardiac function (echocardiography and MRI), histology and transcriptomics were blindly assessed 4-6 weeks after injections. Results: There was no proliferation of cardiomyocytes in either transgenic mouse strains. Nevertheless, EV improved cardiac function in both models. In MerCreMer/ZEG mice, LVEF increased by 18.3 ± 0.2% between baseline and the end-study time point in EV-treated hearts which contrasted with a decrease by 2.3 ± 0.2% in the PBS group; MADM mice featured a similar pattern as intra-myocardial administration of EV improved LVEF by 13.3 ± 0.16% from baseline whereas it decreased by 14.4 ± 0.16% in the control PBS-injected group. This functional improvement was confirmed by MRI and associated with a reduction in infarct size, the decreased expression of several pro-fibrotic genes and an overexpression of the anti-fibrotic miRNA 133-a1 compared to controls. Experiments with an anti-miR133-a demonstrated that the cardio-reparative effects of EV were partly abrogated. Conclusions: EV-CPC do not trigger cardiomyocyte proliferation but still improve cardiac function by other mechanisms which may include the regulation of fibrosis.