Rear cortex contraction aids in nuclear transit during confined migration by increasing pressure in the cell posterior.

As cells migrate through biological tissues, they must frequently squeeze through micron-sized constrictions in the form of interstitial pores between extracellular matrix fibers and/or other cells. Although it is now well recognized that such confined migration is limited by the nucleus, which is the largest and stiffest organelle, it remains incompletely understood how cells apply sufficient force to move their nucleus through small constrictions. Here, we report a mechanism by which contraction of the cell rear cortex pushes the nucleus forward to mediate nuclear transit through constrictions. Laser ablation of the rear cortex reveals that pushing forces behind the nucleus are the result of increased intracellular pressure in the rear compartment of the cell. The pushing forces behind the nucleus depend on accumulation of actomyosin in the rear cortex and require Rho-kinase (ROCK) activity. Collectively, our results suggest a mechanism by which cells generate elevated, intracellular pressure in the posterior compartment to facilitate nuclear transit through 3D constrictions. This mechanism may supplement or even substitute for other mechanisms supporting nuclear transit, ensuring robust cell migrations in confined 3D environments.

Microinterfaces in biopolymer-based bicontinuous hydrogels guide rapid 3D cell migration.

Cell migration is critical for tissue development and regeneration but requires extracellular environments that are conducive to motion. Cells may actively generate migratory routes in vivo by degrading or remodeling their environments or instead utilize existing extracellular matrix microstructures or microtracks as innate pathways for migration. While hydrogels in general are valuable tools for probing the extracellular regulators of 3-dimensional migration, few recapitulate these natural migration paths. Here, we develop a biopolymer-based bicontinuous hydrogel system that comprises a covalent hydrogel of enzymatically crosslinked gelatin and a physical hydrogel of guest and host moieties bonded to hyaluronic acid. Bicontinuous hydrogels form through controlled solution immiscibility, and their continuous subdomains and high micro-interfacial surface area enable rapid 3D migration, particularly when compared to homogeneous hydrogels. Migratory behavior is mesenchymal in nature and regulated by biochemical and biophysical signals from the hydrogel, which is shown across various cell types and physiologically relevant contexts (e.g., cell spheroids, ex vivo tissues, in vivo tissues). Our findings introduce a design that leverages important local interfaces to guide rapid cell migration.

3D Traction Force Microscopy in Biological Gels: From Single Cells to Multicellular Spheroids.

Cell traction force plays a critical role in directing cellular functions, such as proliferation, migration, and differentiation. Current understanding of cell traction force is largely derived from 2D measurements where cells are plated on 2D substrates. However, 2D measurements do not recapitulate a vital aspect of living systems, that is, cells actively remodel their surrounding extracellular matrix (ECM), and the remodeled ECM, in return, can have a profound impact on cell phenotype and traction force generation. This reciprocal adaptivity of living systems is encoded in the material properties of biological gels. In this review, we summarize recent progress in measuring cell traction force for cells embedded within 3D biological gels, with an emphasis on cell-ECM cross talk. We also provide perspectives on tools and techniques that could be adapted to measure cell traction force in complex biochemical and biophysical environments. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 26 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

CD44 and ß1-integrin are both engaged in cell traction force generation in hyaluronic acid-rich extracellular matrices.

Mechanical properties of the extracellular matrices (ECMs) critically regulate a number of important cell function including growth, differentiation and migration. Type I collagen and glycosaminoglycans (GAGs) are two primary components of ECMs that contribute to tissue mechanics with the collagen fiber network sustaining tension and GAGs withstanding compression. Collagen stiffness as well as its architecture are known to be important role players in cell-ECM mechanical interactions, however, much less is known about how GAGs within ECMs regulate cell force generation and invasion. Inspired by a recent theoretical work from the Shenoy lab that GAGs play important roles in cell - ECM interactions, we hereby present experimental studies on the role of hyaluronic acid (HA, an unsulfated GAG) in single tumor cell traction force generation within HA collagen cogels using a recently developed 3D cell traction force microscopy. Our work revealed that CD44, a cell surface adhesion receptor to HA, was engaged in cell traction force generation in conjunction with ß1-integrin. Furthermore, we found that HA significantly modified the architecture and mechanics of the collagen fiber network, decreased tumor cells' propensity to remodel the collagen network, decreased traction force generation and transmission distance, and attenuated tumor invasion in agreement with theoretical predictions. Our findings highlighted the significance of CD44 and HA engagement in cell-ECM mechanical interactions, providing new insights on the mechanical model of cellular force transmission.

Hemodynamic Reactivity to Mental Stress in Patients With Coronary Artery Disease.

Importance: The clinical significance of hemodynamic reactivity to mental stress in the population with coronary artery disease (CAD) is unclear. Objective: To investigate the association between hemodynamic reactivity to mental stress and the risk of adverse cardiovascular events in patients with stable CAD. Design, Setting, and Participants: This cohort study included individuals with stable CAD from 2 prospective studies from a university-based hospital network: the Mental Stress Ischemia Prognosis Study (MIPS) and the Myocardial Infarction and Mental Stress Study 2 (MIMS2). Participants were enrolled between June 2011 and March 2016 and followed up for a median of 6.0 (IQR, 5.6-6.0) years in MIPS and 4.6 (IQR, 3.8-5.3) years in MIMS2. Data were analyzed from December 1, 2022, to February 15, 2023. Exposures: The rate-pressure product (RPP) was calculated as the mean systolic blood pressure times the mean heart rate at rest. Rate-pressure product reactivity was calculated as the maximum RPP during a standardized mental stress test minus the RPP at rest. Main Outcomes and Measures: The primary outcome was a composite of cardiovascular death or nonfatal myocardial infarction. The secondary end point additionally included hospitalizations for heart failure. Results: From the total of 938 individuals from the pooled cohort (mean [SD] age, 60.2 [10.1] years; 611 [65.1%] men), 631 participated in MIPS and 307 in MIMS2. A total of 373 individuals (39.8%) were Black, 519 (55.3%) were White, and 46 (4.9%) were of unknown race or ethnicity. The RPP increased by a mean (SD) of 77.1% (23.1%) during mental stress (mean [SD] absolute change, 5651 [2878]). For every SD decrease in RPP reactivity with mental stress, the adjusted hazard ratios for the primary and secondary end points were 1.30 (95% CI, 1.04-1.72) and 1.30 (95% CI, 1.06-1.56), respectively, in MIPS and 1.41 (95% CI, 1.06-1.97) and 1.21 (95% CI, 1.02-1.60), respectively, in MIMS2. In the pooled sample, when RPP reactivity to mental stress was added to a model including traditional clinical risk characteristics, model discrimination for adverse events improved (increase in C statistic of 5% for the primary end point; P = .009). Conclusions and Relevance: In this cohort study of individuals with stable CAD, a blunted cardiovascular reactivity to mental stress was associated with adverse outcomes. Future studies are needed to assess the clinical utility of mental stress reactivity testing in this population.

Microinterfaces in bicontinuous hydrogels guide rapid 3D cell migration.

Cell migration is critical for tissue development and regeneration but requires extracellular environments that are conducive to motion. Cells may actively generate migratory routes in vivo by degrading or remodeling their environments or may instead utilize existing ECM microstructures or microtracks as innate pathways for migration. While hydrogels in general are valuable tools for probing the extracellular regulators of 3D migration, few have recapitulated these natural migration paths. Here, we developed a biopolymer-based (i.e., gelatin and hyaluronic acid) bicontinuous hydrogel system formed through controlled solution immiscibility whose continuous subdomains and high micro-interfacial surface area enabled rapid 3D migration, particularly when compared to homogeneous hydrogels. Migratory behavior was mesenchymal in nature and regulated by biochemical and biophysical signals from the hydrogel, which was shown across various cell types and physiologically relevant contexts (e.g., cell spheroids, ex vivo tissues, in vivo tissues). Our findings introduce a new design that leverages important local interfaces to guide rapid cell migration.

Subtle adversarial image manipulations influence both human and machine perception.

Although artificial neural networks (ANNs) were inspired by the brain, ANNs exhibit a brittleness not generally observed in human perception. One shortcoming of ANNs is their susceptibility to adversarial perturbations-subtle modulations of natural images that result in changes to classification decisions, such as confidently mislabelling an image of an elephant, initially classified correctly, as a clock. In contrast, a human observer might well dismiss the perturbations as an innocuous imaging artifact. This phenomenon may point to a fundamental difference between human and machine perception, but it drives one to ask whether human sensitivity to adversarial perturbations might be revealed with appropriate behavioral measures. Here, we find that adversarial perturbations that fool ANNs similarly bias human choice. We further show that the effect is more likely driven by higher-order statistics of natural images to which both humans and ANNs are sensitive, rather than by the detailed architecture of the ANN.

A Pilot Study of Neurobiological Mechanisms of Stress and Cardiovascular Risk.

Objective: Coronary heart disease is a leading cause of death and disability. Although psychological stress has been identified as an important potential contributor, mechanisms by which stress increases risk of heart disease and mortality are not fully understood. The purpose of this study was to assess mechanisms by which stress acts through the brain and heart to confer increased CHD risk. Methods: Coronary Heart Disease patients (N=10) underwent cardiac imaging with [Tc-99m] sestamibi single photon emission tomography at rest and during a public speaking mental stress task. Patients returned for a second day and underwent positron emission tomography imaging of the brain, heart, bone marrow, aorta (indicating inflammation) and subcutaneous adipose tissue, after injection of [18F]2-fluoro-2-deoxyglucose for assessment of glucose uptake followed mental stress. Patients with (N=4) and without (N=6) mental stress-induced myocardial ischemia were compared for glucose uptake in brain, heart, adipose tissue and aorta with mental stress. Results: Patients with mental stress-induced ischemia showed a pattern of increased uptake in the heart, medial prefrontal cortex, and adipose tissue with stress. In the heart disease group as a whole, activity increase with stress in the medial prefrontal brain and amygdala correlated with stress-induced increases in spleen (r=0.69, p=0.038; and r=0.69, p=0.04 respectfully). Stress-induced frontal lobe increased uptake correlated with stress-induced aorta uptake (r=0.71, p=0.016). Activity in insula and medial prefrontal cortex was correlated with post-stress activity in bone marrow and adipose tissue. Activity in other brain areas not implicated in stress did not show similar correlations. Increases in medial prefrontal activity with stress correlated with increased cardiac glucose uptake with stress, suggestive of myocardial ischemia (r=0.85, p=0.004). Conclusions: These findings suggest a link between brain response to stress in key areas mediating emotion and peripheral organs involved in inflammation and hematopoietic activity, as well as myocardial ischemia, in Coronary Heart Disease patients.

Lipid-Lowering Nutraceuticals for an Integrative Approach to Dyslipidemia.

Dyslipidemia is a treatable risk factor for atherosclerotic cardiovascular disease that can be addressed through lifestyle changes and/or lipid-lowering therapies. Adherence to statins can be a clinical challenge in some patients due to statin-associated muscle symptoms and other side effects. There is a growing interest in integrative cardiology and nutraceuticals in the management of dyslipidemia, as some patients desire or are actively seeking a more natural approach. These agents have been used in patients with and without established atherosclerotic cardiovascular disease. We provide an updated review of the evidence on many new and emerging nutraceuticals. We describe the mechanism of action, lipid-lowering effects, and side effects of many nutraceuticals, including red yeast rice, bergamot and others.

Ocular Impression-Based Scleral Lens With Wavefront-Guided Optics for Visual Improvement in Keratoconus.

ABSTRACT: This case reports on the use of wavefront-guided (wfg) optics on custom ocular impression-based scleral lenses (IBSLs) for visual improvement in a patient with keratoconus (KC). A 28-year-old man with KC, who had previously failed a traditional, diagnostically fit scleral lens (tSL), was fit with IBSLs with traditional optics. Using a system that included a dot matrix on the IBSL and a wavefront aberrometer with pupil and dot registration software, a wfgIBSL was created. When compared with the IBSL, the wfgIBSL reduced the total higher-order root mean square (HORMS) 67% and 64% in the right and left eye, respectively, resulting in a 2-line improvement in best-contact lens visual acuity (BCLVA) for both eyes. This case demonstrates the successful creation and application of a wfgIBSL resulting in a stable lens, a reduction in HORMS, and an improvement in BCLVA, after failure with a diagnostically fit tSL.

Spatial and temporal dynamics of RhoA activities of single breast tumor cells in a 3D environment revealed by a machine learning-assisted FRET technique.

One of the hallmarks of cancer cells is their exceptional ability to migrate within the extracellular matrix (ECM) for gaining access to the circulatory system, a critical step of cancer metastasis. RhoA, a small GTPase, is known to be a key molecular switch that toggles between actomyosin contractility and lamellipodial protrusion during cell migration. Current understanding of RhoA activity in cell migration has been largely derived from studies of cells plated on a two-dimensional (2D) substrate using a FRET biosensor. There has been increasing evidence that cells behave differently in a more physiologically relevant three-dimensional (3D) environment. However, studies of RhoA activities in 3D have been hindered by low signal-to-noise ratio in fluorescence imaging. In this paper, we present a a machine learning-assisted FRET technique to follow the spatiotemporal dynamics of RhoA activities of single breast tumor cells (MDA-MB-231) migrating in a 3D as well as a 2D environment. We found that RhoA activity is more polarized along the long axis of the cell for single cells migrating on 2D fibronectin-coated glass versus those embedded in 3D collagen matrices. In particular, RhoA activities of cells in 2D exhibit a distinct front-to-back and back-to-front movement during migration in contrast to those in 3D. Finally, regardless of dimensionality, RhoA polarization is found to be moderately correlated with cell shape.

Acute suppurative thyroiditis seeded from infective endocarditis and intravenous drug use.

Acute suppurative thyroiditis (AST) is a rare infection of the thyroid gland, and most patients are euthyroid upon presentation. We present an interesting case of a 42-year-old man with a history of intravenous drug use (IVDU) and poorly controlled type 2 diabetes mellitus who was admitted for sepsis and thyrotoxicosis from infective endocarditis (IE), AST, prostate abscess, and pyelonephritis. He suffered from a cerebral vascular accident (CVA) from septic embolic showering. Thyroid-stimulating hormone (TSH) was <0.10 mIU/L, and free thyroxine (T4) levels were>90 pmol/L. Methicillin-resistant Staphylococcus aureus (MRSA) was cultured in the patient's blood and urine. He was treated with prompt intravenous (IV) antimicrobials and source control from a transurethral resection of the prostate. This case demonstrates that AST can be a potential complication of IE and IVDU.

Remote monitoring of head and neck free flaps using near infrared spectroscopic tissue oximetry.

PURPOSE: Near infrared spectroscopy (NIRS) measures tissue oximetry and perfusion of free tissue transfer with the advantage of remote wireless monitoring for free tissue transfer. It has been widely used in breast and extremity reconstruction but has had limited adoption in the head and neck. MATERIALS AND METHODS: A retrospective review of head and neck microvascular reconstruction by three different surgical services over 15 months at one tertiary care hospital was performed. Demographics, flap type, monitoring technique, complications, and flap outcomes were recorded. Monitoring techniques were (1) implantable/handheld Doppler or (2) NIRS. Flap monitoring outcomes were evaluated using multivariate analysis. RESULTS: 119 flaps were performed by four surgeons with a success rate of 92% (109/119). Flaps were monitored with Doppler (40%) or NIRS (60%). There was no difference in flap success based on monitoring technique. An ROC analysis identified that the optimal cutoff in immediate StO2 for classifying flap success at discharge was 68%. CONCLUSIONS: NIRS was successfully implemented in a high-volume head and neck reconstructive practice. NIRS remote monitoring allowed for flap surveillance without requiring in-hospital presence and was able to identify both arterial and venous compromise.

First-Degree Atrioventricular Block with Tachycardia from Paliperidone and Mirtazapine Overdose.

BACKGROUND: Paliperidone and mirtazapine are psychotropic agents associated with proarrhythmic effects. CASE PRESENTATION: A 21-year-old woman was admitted to the intensive care unit on two separate occasions for attempting suicide by overdosing on paliperidone and mirtazapine. During both admissions, the patient had atypical chest pain and a first-degree atrioventricular block (AVB) with paradoxical sinus tachycardia, which resolved with the discontinuation of paliperidone and mirtazapine and aggressive intravenous fluids. CONCLUSION: Drug-induced first-degree AVB from paliperidone and mirtazapine should be on the differential diagnosis in patients on paliperidone and/or mirtazapine who present with chest pain, tachycardia or new-onset first-degree AVB. LEARNING POINTS: Paliperidone and mirtazapine are associated with first-degree heart block, which may be a harbinger of torsades de pointes and ventricular fibrillation.Paliperidone and mirtazapine may potentiate each other's proarrhythmic effects since the metabolism of both involve the cytochrome P450 2D6 enzyme.A history of psychiatric illness makes it difficult to rule out atypical chest pain without ECG or troponins and often leads to increased resource utilization, even during times of heavy use like the COVID-19 pandemic.

Embolic Showering from Non-Bacterial Thrombotic Endocarditis and Adenocarcinoma of the Lung.

BACKGROUND: Non-bacterial thrombotic endocarditis (NBTE) is a paraneoplastic phenomenon with sterile vegetations. It is associated with adenocarcinoma and can shower emboli, which can be the presenting symptom. CASE PRESENTATION: A 44-year-old woman with adenocarcinoma of the lung presented with chest pain, left hand weakness, and ataxia due to repeated embolic showering from NBTE to the central nervous system (CNS) and spleen. CONCLUSION: NBTE is a rare condition that should be on the differential diagnosis in patients with culture-negative endocarditis and a history of adenocarcinoma. LEARNING POINTS: Differentiating non-bacterial thrombotic endocarditis (NBTE) from infective endocarditis can be a diagnostic challenge due to slow growing organisms; laboratory findings that suggest NBTE include the lack of leucocytosis, normal C-reactive protein, negative blood culture sets, and positive antiphospholipid antibodies.Serial transesophageal echocardiogram (TEE) should be performed if suspicion of valvular vegetations is high despite the initial TEE showing no vegetations.The mainstay treatment of NBTE is anticoagulation and addressing the underlying condition.

Balloon Kyphoplasty Complication: A Case of a Lodged Balloon Within the Vertebral Body.

This report describes a case involving a balloon kyphoplasty bone tamp becoming lodged inside the vertebral body and unable to be withdrawn, the first report of its kind in the literature. A board certified interventional pain management physician was performing a balloon kyphoplasty for an L3 osteoporotic vertebral compression fracture using a bipedicular approach with two bone tamps. Cannulation and cavity formation were completed without complication; however, upon removal of the balloons it was noted that one had become lodged in the vertebral body. Several attempts were made to remove the balloon. Neurosurgery and the balloon manufacturer were consulted intraoperative, and it was decided to leave the balloon fragments in situ and complete the interventional fixation of the vertebral body with bone cement. The patient followed up in the clinic several months later without neurologic complications. Postoperative radiography confirmed the presence of a retained foreign body consistent with balloon fragments. Balloon kyphoplasty and its various procedural complications will be discussed, as well as the intraoperative decision making faced when encountering a complication.

Possible Lyme Carditis with Sick Sinus Syndrome.

Borrelia burgdorferi (B. burgdorferi) is a spirochete bacterium that is transmitted via the Ixodes tick. Infection results in Lyme disease with possible cardiac manifestations, which is also known as Lyme carditis. Patients can present with bradycardia due to rapidly fluctuating atrioventricular block (AVB), which is the hallmark of Lyme carditis. However, we present a rare case of sick sinus syndrome (SSS) without AVB in a 47-year-old man with Lyme disease. He initially presented with a headache and subsequently developed new onset bradycardia and a right cranial nerve (CN) VI palsy with diplopia. B. burgdorferi enzyme-linked immunosorbent assay (ELISA) screen and IgM western blot were positive. He was admitted to the intensive care unit. Electrocardiography (EKG) indicated a heart rate in the high 30 s beats per minute (BPM) with several pauses, but no AVB was present. The patient responded well to therapy, and was discharged with an outpatient regimen of doxycycline. Lyme carditis should be considered in patients who develop new onset bradycardia and live in endemic areas.