Effects of altered blood flow induced by the muscle pump on thrombosis in a microfluidic venous valve model

Advances in the diagnosis and treatment of primary deep venous valve insufficiency

Primary deep venous valve insufficiency (PDVVI) is a common lower extremity venous disease in vascular surgery, distinguished from simple lower extremity varicose veins and lower extremity thrombotic diseases, and requires clinical management as a separate disease. Surgical procedures alone in the superficial venous system cannot completely correct valve reflux and venous hypertension and require surgical valve repair. In addition, the development of non-autologous prosthetic valve transplantation provides a new breakthrough point. This article summarizes the diagnostic and therapeutic advances in PDVVI for discussion.

Dysregulated Coagulation in Parkinson's Disease

Parkinson's disease (PD), a prevalent neurodegenerative disorder characterized by dopaminergic neuron degeneration and α-synuclein accumulation, has been increasingly associated with coagulation dysfunction. This review synthesizes emerging evidence linking dysregulated coagulation to PD pathophysiology. We examine the alterations in coagulation parameters, including elevated fibrinogen levels, impaired fibrinolysis, and platelet dysfunction, which collectively contribute to a hypercoagulable state in PD patients. Epidemiological studies have revealed a higher incidence of thrombotic events, such as deep vein thrombosis (DVT) and stroke, among PD patients, suggesting significant comorbidity between PD and coagulation disorders. This review explores the potential pathophysiological mechanisms underlying this association, focusing on the roles of inflammation and oxidative stress. Additionally, we discuss the limitations of current research and propose future directions. This comprehensive analysis underscores the importance of understanding the coagulation-neurodegeneration axis in PD, which may lead to novel diagnostic and therapeutic strategies for this debilitating condition.

A Silent Threat: Deep Vein Thrombosis in Early-Stage Parkinson's Disease

Introduction

The primary clinical manifestation of venous thrombosis is discomfort in the lower extremities. Some early Parkinson's disease (PD) patients feel discomfort in the lower limbs. Venous thrombosis can risk lives by causing pulmonary embolism. This study examines the incidence of DVT in early PD patients and its correlation with different clinical and lab features.

Methods

A cross-sectional study was conducted on 117 patients with early-stage PD. Ultrasonography was employed to detect the presence of DVT. Factors such as age, gender, body mass index, lifestyle habits (smoking and drinking), medical history (hypertension, diabetes, atrial fibrillation, and tumor), and other lab tests linked to thrombosis were analyzed.

Results

In 117 patients, 11 (9.4%) had DVT, while 106 (90.6%) did not. There were no significant differences in gender, BMI, habits, medical history, or other thrombosis-related tests between both groups. However, DVT patients were older with higher d-dimer levels. They also showed an increased right substantia nigra ultrasound echo area, higher HY grades, higher UPDRS 3 scores, less improvement in UPDRS 3 scores and levodopa response.

Discussion

The primary risk factors for lower extremity venous thrombosis were found to be age, d-dimer levels, and low-dose levodopa. Therefore, for elderly patients with early-stage PD, it is crucial to conduct d-dimer and lower extremity vascular ultrasound tests. The prevention of venous thrombosis in the lower extremities of early PD patients is of utmost importance.

The effect of ultrasound-assisted thrombolysis studied in blood-on-a-chip

BACKGROUND

Thromboembolism, which leads to pulmonary embolism and ischemic stroke, remains one of the main causes of death. Ultrasound-assisted thrombolysis (UAT) is an effective thrombolytic method. However, further studies are required to elucidate the mechanism of ultrasound on arterial and venous thrombi.

METHODS

We employed the blood-on-a-chip technology to simulate thrombus formation in coronary stenosis and deep vein valves. Subsequently, UAT was conducted on the chip to assess the impact of ultrasound on thrombolysis under varying flow conditions. Real-time fluorescence was used to assess thrombolysis and drug penetration. Finally, scanning electron microscopy and immunofluorescence were used to determine the effect of ultrasound on fibrinolysis.

RESULTS

The study revealed that UAT enhanced the thrombolytic rate by 40% in the coronary stenosis chip and by 10% in the deep venous valves chip. This enhancement is attributed to the disruption of crosslinked fibrin fibers by ultrasound, leading to increased urokinase diffusion within the thrombus and accumulation of plasminogen on the fibrinogen α chain. Moreover, the acceleration of the dissolution rate of thrombi in the venous valve chip by ultrasound was not as significant as that in the coronary stenosis chip.

CONCLUSION

These findings highlight the differential impact of ultrasound on thrombolysis under various flow conditions and emphasize the valuable role of the blood-on-a-chip technology in exploring thrombolysis mechanisms.

Valve-Adjustable Optofluidic Bio-Imaging Platform for Progressive Stenosis Investigation

The clinical evidence has proven that valvular stenosis is closely related to many vascular diseases, which attracts great academic attention to the corresponding pathological mechanisms. The investigation is expected to benefit from the further development of an in vitro model that is tunable for bio-mimicking progressive valvular stenosis and enables accurate optical recognition in complex blood flow. Here, we develop a valve-adjustable optofluidic bio-imaging recognition platform to fulfill it. Specifically, the bionic valve was designed with in situ soft membrane, and the internal air-pressure chamber could be regulated from the inside out to bio-mimic progressive valvular stenosis. The developed imaging algorithm enhances the recognition of optical details in blood flow imaging and allows for quantitative analysis. In a prospective clinical study, we examined the effect of progressive valvular stenosis on hemodynamics within the typical physiological range of veins by this way, where the inhomogeneity and local enhancement effect in the altered blood flow field were precisely described and the optical differences were quantified. The effectiveness and consistency of the results were further validated through statistical analysis. In addition, we tested it on fluorescence and noticed its good performance in fluorescent tracing of the clotting process. In virtue of theses merits, this system should be able to contribute to mechanism investigation, pharmaceutical development, and therapeutics of valvular stenosis-related diseases.

Wall shear gradient dependent thrombosis studied in blood-on-a-chip with stenotic, branched, and valvular constructions

Thrombosis is the leading cause of death, while the effect of the shear flow on the formation of thrombus in vascular constructions has not been thoroughly understood, and one of the challenges is to observe the origination of thrombus with a controlled flow field. In this work, we use blood-on-a-chip technology to mimic the flow conditions in coronary artery stenosis, neonatal aortic arch, and deep venous valve. The flow field is measured by the microparticle image velocimeter (μPIV). In the experiment, we find that the thrombus often originates at the constructions of stenosis, bifurcation, and the entrance of valve, where the flow stream lines change suddenly, and the maximum wall shear rate gradient appears. Using the blood-on-a-chip technology, the effect of the wall shear rate gradients on the formation of the thrombus has been illustrated, and the blood-on-a-chip is demonstrated to be a perspective tool for further studies on the flow-induced formation of thrombosis.

Platelet accumulation in an endothelium-coated elastic vein valve model of deep vein thrombosis is mediated by GPIbα-VWF interaction

Deep vein thrombosis is a life-threatening disease that takes millions of people's lives worldwide. Given both technical and ethical issues of using animals in research, it is necessary to develop an appropriate in vitro model that would recapitulate the conditions of venous thrombus development. We present here a novel microfluidics vein-on-a-chip with moving valve leaflets to mimic the hydrodynamics in a vein, and Human Umbilical Vein Endothelial Cell (HUVEC) monolayer. A pulsatile flow pattern, typical for veins, was used in the experiments. Unstimulated human platelets, reconstituted with the whole blood, accumulated at the luminal side of the leaflet tips proportionally to the leaflet flexibility. Platelet activation by thrombin induced robust platelet accrual at the leaflet tips. Inhibition of glycoprotein (GP) IIb-IIIa did not decrease but, paradoxically, slightly increased platelet accumulation. In contrast, blockade of the interaction between platelet GPIbα and A1 domain of von Willebrand factor completely abolished platelet deposition. Stimulation of the endothelium with histamine, a known secretagogue of Weibel-Palade bodies, promoted platelet accrual at the basal side of the leaflets, where human thrombi are usually observed. Thus, platelet deposition depends on the leaflet flexibility, and accumulation of activated platelets at the valve leaflets is mediated by GPIbα-VWF interaction.

The interaction of vortical flows with red cells in venous valve mimics

The motion of cells orthogonal to the direction of main flow is of importance in natural and engineered systems. The lateral movement of red blood cells (RBCs) distal to sudden expansion is considered to influence the formation and progression of thrombosis in venous valves, aortic aneurysms, and blood-circulating devices and is also a determining parameter for cell separation applications in flow-focusing microfluidic devices. Although it is known that the unique geometry of venous valves alters the blood flow patterns and cell distribution in venous valve sinuses, the interactions between fluid flow and RBCs have not been elucidated. Here, using a dilute cell suspension in an in vitro microfluidic model of a venous valve, we quantified the spatial distribution of RBCs by microscopy and image analysis, and using micro-particle image velocimetry and 3D computational fluid dynamics simulations, we analyzed the complex flow patterns. The results show that the local hematocrit in the valve pockets is spatially heterogeneous and is significantly different from the feed hematocrit. Above a threshold shear rate, the inertial separation of streamlines and lift forces contribute to an uneven distribution of RBCs in the vortices, the entrapment of RBCs in the vortices, and non-monotonic wall shear stresses in the valve pockets. Our experimental and computational characterization provides insights into the complex interactions between fluid flow, RBC distribution, and wall shear rates in venous valve mimics, which is of relevance to understanding the pathophysiology of thrombosis and improving cell separation efficiency.

Microfluidic models of the human circulatory system: versatile platforms for exploring mechanobiology and disease modeling

The human circulatory system is a marvelous fluidic system, which is very sensitive to biophysical and biochemical cues. The current animal and cell culture models do not recapitulate the functional properties of the human circulatory system, limiting our ability to fully understand the complex biological processes underlying the dysfunction of this multifaceted system. In this review, we discuss the unique ability of microfluidic systems to recapitulate the biophysical, biochemical, and functional properties of the human circulatory system. We also describe the remarkable capacity of microfluidic technologies for exploring the complex mechanobiology of the cardiovascular system, mechanistic studying of cardiovascular diseases, and screening cardiovascular drugs with the additional benefit of reducing the need for animal models. We also discuss opportunities for further advancement in this exciting field.

Microengineered Human Vein-Chip Recreates Venous Valve Architecture and Its Contribution to Thrombosis

Deep vein thrombosis (DVT) and its consequences are lethal, but current models cannot completely dissect its determinants-endothelium, flow, and blood constituents-together called Virchow's triad. Most models for studying DVT forego assessment of venous valves that serve as the primary sites of DVT formation. Therefore, the knowledge of DVT formed at the venous cusps has remained obscure due to lack of experimental models. Here, organ-on-chip methodology is leveraged to create a Vein-Chip platform integrating fully vascularized venous valves and its hemodynamic, as seen in vivo. These Vein-Chips reveal that vascular endothelium of valve cusps adapts to the locally disturbed microenvironment by expressing a different phenotype from the regions of uniform flow. This spatial adaptation of endothelial function recreated on the in vitro Vein-Chip platform is shown to protect the vein from thrombosis from disturbed flow in valves, but interestingly, cytokine stimulation reverses the effect and switches the valve endothelium to becoming prothrombotic. The platform eventually modulates the three factors of Virchow's triad and provides a systematic approach to investigate the determinants of fibrin and platelet dynamics of DVT. Therefore, this Vein-Chip offers a new preclinical approach to study venous pathophysiology and show effects of antithrombotic drug treatment.