Tortuosity-powered microfluidic device for assessment of thrombosis and antithrombotic therapy in whole blood

Recent advances in microfluidic technology of arterial thrombosis investigations

Microfluidic technology has emerged as a powerful tool in studying arterial thrombosis, allowing researchers to construct artificial blood vessels and replicate the hemodynamics of blood flow. This technology has led to significant advancements in understanding thrombosis and platelet adhesion and aggregation. Microfluidic models have various types and functions, and by studying the fabrication methods and working principles of microfluidic chips, applicable methods can be selected according to specific needs. The rapid development of microfluidic integrated system and modular microfluidic system makes arterial thrombosis research more diversified and automated, but its standardization still needs to be solved urgently. One key advantage of microfluidic technology is the ability to precisely control fluid flow in microchannels and to analyze platelet behavior under different shear forces and flow rates. This allows researchers to study the physiological and pathological processes of blood flow, shedding light on the underlying mechanisms of arterial thrombosis. In conclusion, microfluidic technology has revolutionized the study of arterial thrombosis by enabling the construction of artificial blood vessels and accurately reproducing hemodynamics. In the future, microfluidics will place greater emphasis on versatility and automation, holding great promise for advancing antithrombotic therapeutic and prophylactic measures.

Predicting severe proximal left anterior descending coronary artery stenosis using proximal left anterior descending coronary artery tortuosity and the angle between the left main and anterior descending coronary arteries: a retrospective cross-sectional study

Background

Coronary bifurcation angles influence plaque initiation in the coronary artery, and changes in blood flow caused by tortuosity in the coronary arteries can reduce blood pressure distal to the tortuous portion of the coronary artery, leading to myocardial ischemia. We aimed to describe two factors (coronary artery tortuosity and bifurcation angle) as one descriptor for the evaluation of proximal left anterior descending coronary artery (LAD) disease.

Methods

We reviewed the medical records of 133 consecutive patients who underwent computed tomography angiography (CTA) for angina symptoms between November 2019 and January 2020. The patients were divided into two groups according to the presence of significant LAD stenosis on CTA (defined as LAD stenosis >50%). The straight length of the vessel was measured using the central luminal line of the flow path, and, calculated using proprietary algorithms in TeraRecon software. We used three-dimensional volume rendering and two-dimensional axial images to measure the left main coronary artery (LM)-LAD angles.

Results

In the univariate analysis, there were significant differences in the linear distance between the endpoints of the 20 mm actual curve of the LAD (d20), cosine value for LM-LAD angle (cosθ) <0.8, age, presence of hypertension or diabetes, and number of pack years [hazard ratio (HR): 2.70, 8.04, 1.05, 3.70, 2.82, and 1.04; P=0.029, P<0.001, P=0.020, P=0.024, P=0.021, and P=0.002, respectively]. However, in the multivariate analysis, the cosθ multiplied by d20 (d20*cosθ) <15.5, presence of hypertension and number of pack years (HR: 11.36, 4.54, and 1.04; P<0.001, P=0.019, and P=0.003, respectively) were predictors of significant proximal LAD stenosis.

Conclusions

As the tortuosity and LM-LAD angle increased (d20 and cosθ decreased, respectively), the chance of proximal LAD lesions formation increased. d20*cosθ might be useful as a predictor of proximal LAD stenosis.

Model Systems to Study the Mechanism of Vascular Aging

Cardiovascular diseases are the leading cause of death globally. Within cardiovascular aging, arterial aging holds significant importance, as it involves structural and functional alterations in arteries that contribute substantially to the overall decline in cardiovascular health during the aging process. As arteries age, their ability to respond to stress and injury diminishes, while their luminal diameter increases. Moreover, they experience intimal and medial thickening, endothelial dysfunction, loss of vascular smooth muscle cells, cellular senescence, extracellular matrix remodeling, and deposition of collagen and calcium. This aging process also leads to overall arterial stiffening and cellular remodeling. The process of genomic instability plays a vital role in accelerating vascular aging. Progeria syndromes, rare genetic disorders causing premature aging, exemplify the impact of genomic instability. Throughout life, our DNA faces constant challenges from environmental radiation, chemicals, and endogenous metabolic products, leading to DNA damage and genome instability as we age. The accumulation of unrepaired damages over time manifests as an aging phenotype. To study vascular aging, various models are available, ranging from in vivo mouse studies to cell culture options, and there are also microfluidic in vitro model systems known as vessels-on-a-chip. Together, these models offer valuable insights into the aging process of blood vessels.

Nematic Fibrin Fibers Enabling Vascularized Thrombus Implants Facilitate Scarless Cutaneous Wound Healing

Autologous implantable scaffolds that induce vasculogenesis have shown great potential in tissue regeneration; however, previous attempts mainly relied on cell-laden hydrogel patches using fat tissues or platelet-rich plasma, which are insufficient for generating a uniform vasculature in a scalable manner. Here, implantable vascularized engineered thrombi (IVETs) are presented using autologous whole blood, which potentiate effective skin wound healing by constructing robust microcapillary vessel networks at the wound site. Microfluidic shear stresses enable the alignment of bundled fibrin fibers along the direction of the blood flow streamlines and the activation of platelets, both of which offer moderate stiffness of the microenvironment optimal for facilitating endothelial cell maturation and vascularization. Rodent dorsal skin wounds patched with IVET present superior wound closure rates (96.08 ± 1.58%), epidermis thickness, collagen deposition, hair follicle numbers, and neutrophil infiltration, which are permitted by enhanced microvascular circulation. Moreover, IVET treatment accelerates wound healing by recruiting M2 phenotype macrophages.

An Overview of Organ-on-a-Chip Models for Recapitulating Human Pulmonary Vascular Diseases

Traditionally, animal models have been used for recapitulating human physiology and for studying the pathological basis of many diseases affecting humankind. Indeed, over the centuries, animal models helped advance our understanding of the biology and pathology of drug therapy for humans. However, with the advent of genomics and pharmacogenomics, we now know that conventional models cannot accurately capture the pathological conditions and biological processes in humans, although humans share many physiological and anatomical features with many animals [1-3]. Species to species variation have raised concerns about the validity and suitability of animal models for studying human conditions. Over the past decade, the development and advances in microfabrication and biomaterials have spurred the growth in micro-engineered tissue and organ models (organs-on-a-chip, OoC) as alternatives to animal and cellular models [4]. This state-of-the-art technology has been used to emulate human physiology for investigating multitudes of cellular and biomolecular processes implicated in the pathological basis of disease (Fig. 13.1) [4]. Because of their tremendous potential, OoC-based models have been listed as one of the top 10 emerging technologies in the 2016 World Economic Forum [2].

Vascular Transcriptomics: Investigating Endothelial Activation and Vascular Dysfunction Using Blood Outgrowth Endothelial Cells, Organ-Chips, and RNA Sequencing

Vascular organ-chip or vessel-chip technology has significantly impacted our ability to model microphysiological vasculature. These biomimetic platforms have garnered significant interest from scientists and pharmaceutical companies as drug screening models. However, these models still lack the inclusion of patient-specific vasculature in the form of patient-derived endothelial cells. Blood outgrowth endothelial cells are patient blood-derived endothelial progenitors that have gained interest from the vascular biology community as an autologous endothelial cell alternative and have also been incorporated with the vessel-chip model. Next-generation sequencing techniques like RNA sequencing can further unlock the potential of personalized vessel-chips in discerning patient-specific hallmarks of endothelial dysfunction. Here we present a detailed protocol for (1) isolating blood outgrowth endothelial cells from patient blood samples, (2) culturing them in microfluidic vessel-chips, (3) isolating and preparing RNA from individual vessel-chips for sequencing, and (4) performing differential gene expression and bioinformatics analyses of vascular dysfunction and endothelial activation pathways. This method focuses specifically on identification of pathways and genes involved in vascular homeostasis and pathology, but can easily be adapted for the requirements of other systems. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Isolation of blood outgrowth endothelial cells from patient blood Basic Protocol 2: Culture of blood outgrowth endothelial cells in microfluidic vessel-chips Basic Protocol 3: Isolation of RNA from autologous vessel-chips Basic Protocol 4: Differential gene expression and bioinformatics analyses of endothelial activation pathways.

OvCa-Chip microsystem recreates vascular endothelium-mediated platelet extravasation in ovarian cancer

In ovarian cancer, platelet extravasation into the tumor and resulting metastasis is thought to be regulated mostly by the vascular endothelium. Because it is difficult to dissect complex underlying events in murine models, organ-on-a-chip methodology is applied to model vascular and platelet functions in ovarian cancer. This system (OvCa-Chip) consists of microfluidic chambers that are lined by human ovarian tumor cells interfaced with a 3-dimensional endothelialized lumen. Subsequent perfusion with human platelets within the device's vascular endothelial compartment under microvascular shear conditions for 5 days uncovered organ-to-molecular-level contributions of the endothelium to triggering platelet extravasation into tumors. Further, analysis of effluents available from the device's individual tumor and endothelial chambers revealed temporal dynamics of vascular disintegration caused by cancer cells, a differential increase in cytokine expression, and an alteration of barrier maintenance genes in endothelial cells. These events, when analyzed within the device over time, made the vascular tissue leaky and promoted platelet extravasation. Atorvastatin treatment of the endothelial cells within the OvCa-Chip revealed improved endothelial barrier function, reduction in inflammatory cytokines and, eventually, arrest of platelet extravasation. These data were validated through corresponding observations in patient-derived tumor samples. The OvCa-Chip provides a novel in vitro dissectible platform to model the mechanisms of the cancer-vascular-hematology nexus and the analyses of potential therapeutics.

Microfluidic and Organ-on-a-Chip Approaches to Investigate Cellular and Microenvironmental Contributions to Cardiovascular Function and Pathology

Over the past decade, advances in microfabrication and biomaterials have facilitated the development of microfluidic tissue and organ models to address challenges with conventional animal and cell culture systems. These systems have largely been developed for human disease modeling and preclinical drug development and have been increasingly used to understand cellular and molecular mechanisms, particularly in the cardiovascular system where the characteristic mechanics and architecture are difficult to recapitulate in traditional systems. Here, we review recent microfluidic approaches to model the cardiovascular system and novel insights provided by these systems. Key features of microfluidic approaches include the ability to pattern cells and extracellular matrix (ECM) at cellular length scales and the ability to use patient-derived cells. We focus the review on approaches that have leveraged these features to explore the relationship between genetic mutations and the microenvironment in cardiovascular disease progression. Additionally, we discuss limitations and benefits of the various approaches, and conclude by considering the role further advances in microfabrication technology and biochemistry techniques play in establishing microfluidic cardiovascular disease models as central tools for understanding biological mechanisms and for developing interventional strategies.

Acute and Chronic Cardiovascular Manifestations of COVID-19: Role for Endotheliopathy

SARS-CoV-2, the virus that causes coronavirus disease 19 (COVID-19), is associated with a bewildering array of cardiovascular manifestations, including myocardial infarction and stroke, myocarditis and heart failure, atrial and ventricular arrhythmias, venous thromboembolism, and microvascular disease. Accumulating evidence indicates that a profound disturbance of endothelial homeostasis contributes to these conditions. Furthermore, the pulmonary infiltration and edema, and later pulmonary fibrosis, in patients with COVID-19 is promoted by endothelial alterations including the expression of endothelial adhesion molecules and chemokines, increased intercellular permeability, and endothelial-to-mesenchyme transitions. The cognitive disturbance occurring in this disease may also be due in part to an impairment of the blood-brain barrier. Venous thrombosis and pulmonary thromboembolism are most likely associated with an endothelial defect caused by circulating inflammatory cytokines and/or direct endothelial invasion by the virus. Endothelial-targeted therapies such as statins, nitric oxide donors, and antioxidants may be useful therapeutic adjuncts in COVID-19 by restoring endothelial homeostasis.