Vascular smooth muscle cell glycocalyx mediates shear stress-induced contractile responses via a Rho kinase (ROCK)-myosin light chain phosphatase (MLCP) pathway

Elucidating VSMC phenotypic transition mechanisms to bridge insights into cardiovascular disease implications

Cardiovascular diseases (CVD) are the leading cause of death worldwide, despite advances in understanding cardiovascular health. Significant barriers still exist in effectively preventing and managing these diseases. Vascular smooth muscle cells (VSMCs) are crucial for maintaining vascular integrity and can switch between contractile and synthetic functions in response to stimuli such as hypoxia and inflammation. These transformations play a pivotal role in the progression of cardiovascular diseases, facilitating vascular modifications and disease advancement. This article synthesizes the current understanding of the mechanisms and signaling pathways regulating VSMC phenotypic transitions, highlighting their potential as therapeutic targets in cardiovascular disease interventions.

The potential involvement of glycocalyx disruption in abdominal aortic aneurysm pathogenesis

BACKGROUND

Abdominal aortic aneurysm is a weakening and expansion of the abdominal aorta. Currently, there is no drug treatment to limit abdominal aortic aneurysm growth. The glycocalyx is the outermost layer of the cell surface, mainly composed of glycosaminoglycans and proteoglycans.

OBJECTIVE

The aim of this review was to identify a potential relationship between glycocalyx disruption and abdominal aortic aneurysm pathogenesis.

METHODS

A narrative review of relevant published research was conducted.

RESULTS

Glycocalyx disruption has been reported to enhance vascular permeability, impair immune responses, dysregulate endothelial function, promote extracellular matrix remodeling and modulate mechanotransduction. All these effects are implicated in abdominal aortic aneurysm pathogenesis. Glycocalyx disruption promotes inflammation through exposure of adhesion molecules and release of proinflammatory mediators. Glycocalyx disruption affects how the endothelium responds to shear stress by reducing nitric oxide availabilty and adversely affecting the storage and release of several antioxidants, growth factors, and antithromotic proteins. These changes exacerbate oxidative stress, stimulate vascular smooth muscle cell dysfunction, and promote thrombosis, all effects implicated in abdominal aortic aneurysm pathogenesis. Deficiency of key component of the glycocalyx, such as syndecan-4, were reported to promote aneurysm formation and rupture in the angiotensin-II and calcium chloride induced mouse models of abdominal aortic aneurysm.

CONCLUSION

This review provides a summary of past research which suggests that glycocalyx disruption may play a role in abdominal aortic aneurysm pathogenesis. Further research is needed to establish a causal link between glycocalyx disruption and abdominal aortic aneurysm development.

Interstitial Fluid Shear Stress Induces the Synthetic Phenotype Switching of VSMCs to Release Pro-calcified Extracellular Vesicles via EGFR-MAPK-KLF5 Pathway

Phenotypic switching (from contractile to synthetic) of vascular smooth muscle cells (VSMCs) is essential in the progression of atherosclerosis. The damaged endothelium in the atherosclerotic artery exposes VSMCs to increased interstitial fluid shear stress (IFSS). However, the precise mechanisms by which increased IFSS influences VSMCs phenotypic switching are unrevealed. Here, we employed advanced numerical simulations to calculate IFSS values accurately based on parameters acquired from patient samples. We then carefully investigated the phenotypic switching and extracellular vesicles (EVs) secretion of VSMCs under various IFSS conditions. By employing a comprehensive set of approaches, we found that VSMCs exhibited synthetic phenotype upon atherosclerotic IFSS. This synthetic phenotype is the upstream regulator for the enhanced secretion of pro-calcified EVs. Mechanistically, as a mechanotransducer, the epidermal growth factor receptor (EGFR) initiates the flow-based mechanical cues to MAPK signaling pathway, facilitating the nuclear accumulation of the transcription factor krüppel-like factor 5 (KLF5). Furthermore, pharmacological inhibiting either EGFR or MAPK signaling pathway blocks the nuclear accumulation of KLF5 and finally results in the maintenance of contractile VSMCs even under increased IFSS stimulation. Collectively, targeting this signaling pathway holds potential as a novel therapeutic strategy to inhibit VSMCs phenotypic switching and mitigate the progression of atherosclerosis.

Interstitial flow, pressure and residual stress in the aging carotid artery model in FEBio

Vascular smooth muscle cells (VSMCs) are subject to interstitial flow-induced shear stress, which is a critical parameter in cardiovascular disease progression. Transmural pressure loading and residual stresses alter the hydraulic conductivity of the arterial layers and modulate the interstitial fluid flux through the arterial wall. In this paper, a biphasic multilayer model of a common carotid artery (CCA) with anisotropic fiber-reinforced soft tissue and strain-dependent permeability is developed in FEBio software. After the verification of the numerical predictions, age-related arterial thickening and stiffening effects on arterial deformation and interstitial flow are computed under physiological geometry and physical parameters. We found that circumferential residual stress shifts outward in each layer and its gradient increases up to 6 times with aging. Internally pressurized CCA displays nonlinear deformation. In the aged artery, the circumferential stress becomes greater on the media layer (82-158 kPa) and lower on the intima and adventitia (19-23 kPa and 25-28 kPa, respectively). The radial compression of the intima reduces the total hydraulic conductivity by 48% in the young and 16% in the aged arterial walls. Consequently, the average radial interstitial flux increases with pressure by 14% in the young and 91% in the aged arteries. Accordingly, the flow shear stress experienced by the VSMCs becomes more significant for aged arteries, which may accelerate cardiovascular disease progression compared to young arteries.

A simple and accurate method to quantify real-time contraction of vascular smooth muscle cell in vitro

Vascular smooth muscle cells (VSMCs) constitute the medial layer of the blood vessel wall. Their contractile state regulates blood flow in physiological and pathological conditions. Current methods for assessing the contractility of VSMCs are not amenable to the high-throughput screening of pharmaceutical compounds. This study aimed to develop a method to address this shortcoming in the field. Real-time contraction was visualized in living VSMCs using the exogenous expression of green fluorescent protein (GFP). Image-Pro Plus software (IPPS) was used to measure various morphological cell indices. In phenylephrine-treated VSMCs, GFP fluorescence imaging was more accurate than brightfield imaging or phalloidin staining in representing VSMC morphology, as measured using IPPS. Among the multiple indices of VSMC shape, area and mean-diameter were more sensitive than length in reflecting the morphological changes in VSMC. We developed a new index, compound length, by combining the mean-diameter and length to differentiate contracted and uncontracted VSMCs. Based on the compound length, we further generated a contraction index to define a single-VSMC contractile status as single-VSMC contraction-index (SVCI). Finally, compound length and SVCI were validated to effectively assess cell contraction in VSMCs challenged with U46619 and KCl. In conclusion, GFP-based indices of compound length and SVCI can accurately quantify the real-time contraction of VSMCs. In future, the new method will be applied to high-throughput drug screening or basic cardiovascular research.

Cell response to mechanical microenvironment cues via Rho signaling: From mechanobiology to mechanomedicine

Mechanical cues in the cell microenvironment such as those from extracellular matrix properties, stretching, compression and shear stress, play a critical role in maintaining homeostasis. Upon sensing mechanical stimuli, cells can translate these external forces into intracellular biochemical signals to regulate their cellular behaviors, but the specific mechanisms of mechanotransduction at the molecular level remain elusive. As a subfamily of the Ras superfamily, Rho GTPases have been recognized as key intracellular mechanotransduction mediators that can regulate multiple cell activities such as proliferation, migration and differentiation as well as biological processes such as cytoskeletal dynamics, metabolism, and organ development. However, the upstream mechanosensors for Rho proteins and downstream effectors that respond to Rho signal activation have not been well illustrated. Moreover, Rho-mediated mechanical signals in previous studies are highly context-dependent. In this review, we systematically summarize the types of mechanical cues in the cell microenvironment and provide recent advances on the roles of the Rho-based mechanotransduction in various cell activities, physiological processes and diseases. Comprehensive insights into the mechanical roles of Rho GTPase partners would open a new paradigm of mechanomedicine for a variety of diseases. STATEMENT OF SIGNIFICANCE: In this review, we highlight the critical role of Rho GTPases as signal mediators to respond to physical cues in microenvironment. This article will add a distinct contribution to this set of knowledge by intensively addressing the relationship between Rho signaling and mechanobiology/mechanotransduction/mechanomedcine. This topic has not been discussed by the journal, nor has it yet been developed by the field. The comprehensive picture that will develop, from molecular mechanisms and engineering methods to disease treatment strategies, represents an important and distinct contribution to the field. We hope that this review would help researchers in various fields, especially clinicians, oncologists and bioengineers, who study Rho signal pathway and mechanobiology/mechanotransduction, understand the critical role of Rho GTPase in mechanotransduction.

Flow-induced glycocalyx formation and cell alignment of HUVECs compared to iPSC-derived ECs for tissue engineering applications

The relevance of cellular in vitro models highly depends on their ability to mimic the physiological environment of the respective tissue or cell niche. Static culture conditions are often unsuitable, especially for endothelial models, since they completely neglect the physiological surface shear stress and corresponding reactions of endothelial cells (ECs) such as alignment in the direction of flow. Furthermore, formation and maturation of the glycocalyx, the essential polysaccharide layer covering all endothelial surfaces and regulating diverse processes, is highly dependent on applied fluid flow. This fragile but utterly important macromolecular layer is hard to analyze, its importance is often underestimated and accordingly neglected in many endothelial models. Therefore, we exposed human umbilical vein ECs (HUVECs) and human induced pluripotent stem cell-derived ECs (iPSC-ECs) as two relevant EC models in a side-by-side comparison to static and physiological dynamic (6.6 dyn cm-2) culture conditions. Both cell types demonstrated an elongation and alignment along the flow direction, some distinct changes in glycocalyx composition on the surface regarding the main glycosaminoglycan components heparan sulfate, chondroitin sulfate or hyaluronic acid as well as an increased and thereby improved glycocalyx thickness and functionality when cultured under homogeneous fluid flow. Thus, we were able to demonstrate the maturity of the employed iPSC-EC model regarding its ability to sense fluid flow along with the general importance of physiological shear stress for glycocalyx formation. Additionally, we investigated EC monolayer integrity with and without application of surface shear stress, revealing a comparable existence of tight junctions for all conditions and a reorganization of the cytoskeleton upon dynamic culture leading to an increased formation of focal adhesions. We then fabricated cell sheets of EC monolayers after static and dynamic culture via non-enzymatic detachment using thermoresponsive polymer coatings as culture substrates. In a first proof-of-concept we were able to transfer an aligned iPSC-EC sheet to a 3D-printed scaffold thereby making a step in the direction of vascular modelling. We envision these results to be a valuable contribution to improvements of in vitro endothelial models and vascular engineering in the future.

Vascular Smooth Muscle Cells Mechanosensitive Regulators and Vascular Remodeling

Blood vessels are subjected to mechanical loads of pressure and flow, inducing smooth muscle circumferential and endothelial shear stresses. The perception and response of vascular tissue and living cells to these stresses and the microenvironment they are exposed to are critical to their function and survival. These mechanical stimuli not only cause morphological changes in cells and vessel walls but also can interfere with biochemical homeostasis, leading to vascular remodeling and dysfunction. However, the mechanisms underlying how these stimuli affect tissue and cellular function, including mechanical stimulation-induced biochemical signaling and mechanical transduction that relies on cytoskeletal integrity, are unclear. This review focuses on signaling pathways that regulate multiple biochemical processes in vascular mesangial smooth muscle cells in response to circumferential stress and are involved in mechanosensitive regulatory molecules in response to mechanotransduction, including ion channels, membrane receptors, integrins, cytoskeletal proteins, nuclear structures, and cascades. Mechanoactivation of these signaling pathways is closely associated with vascular remodeling in physiological or pathophysiological states.

Transcriptomic analysis reveals that coxsackievirus B3 Woodruff and GD strains use similar key genes to induce FoxO signaling pathway activation in HeLa cells

Coxsackievirus B3 (CVB3) is a major cause of viral myocarditis in humans. Although there have been studies on CVB3 infection and pathogenesis, the precise disease mechanism is still not clear. In this study, we used RNA-seq technology to compare the transcriptomic profile of virus-infected HeLa cells to that of uninfected cells to identify key genes involved in host-virus interaction. For this, two CVB3 strains, CVB3 Woodruff, an experimental strain, and GD16-69/GD/CHN/2016, a clinical strain, were selected to examine the common mechanisms underlying their infection. Transcriptomic profiles revealed increased expression of the cell cycle genes CCNG2, GADD45B, PIM1, RBM15, KLF10, and RIOK3 and decreased expression of CYBA. The autophagy-related genes ATG12 and YOD1 were found to be upregulated, while the expression of SOD2 and XPO1 increased slightly in infected cells, and only a minor change was observed in GABARAP expression. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed the FoxO signaling pathway to be enriched and showed a close interaction with differentially expressed genes (DEGs) in the protein-protein interaction network. DEGs associated with related pathways such as cell cycle, autophagy, and oxidative stress resistance were also confirmed by qRT-PCR. In summary, the FoxO signaling pathway was activated during infection with both CVB3 strains and was found to have a regulatory role in downstream pathways such as cell cycle, autophagy, oxidative stress resistance, and the antiviral immune response.

Mechanical and chemical cues synergistically promote human venous smooth muscle cell osteogenesis through integrin β1-ERK1/2 signaling: A cell model of hemodialysis fistula calcification

Arteriovenous fistula (AVF) is the vascular access of choice for renal replacement therapy. However, AVF is susceptible to calcification with a high prevalence of 40%-65% in chronic hemodialysis patients. Repeated needle puncture for hemodialysis cannulation results in intimal denudation of AVF. We hypothesized that exposure to blood shear stress in the medial layer promotes venous smooth muscle cell (SMC) osteogenesis. While previous studies of shear stress focused on arterial-type SMCs, SMCs isolated from the vein had not been investigated. This study established a venous cell model of AVF using the fluid shear device, combined with a high phosphate medium to mimic the uremic milieu. Osteogenic gene expression of venous SMCs upon mechanical and chemical cues was analyzed in addition to the activated cell signaling pathways. Our findings indicated that upon shear stress and high phosphate environment, mechanical stimulation (shear stress) had an additive effect in up-regulation of an early osteogenic marker, Runx2. We further identified that the integrin β1-ERK1/2 signaling pathway was responsible for the molecular basis of venous SMC osteogenesis upon shear stress exposure. Mitochondrial biogenesis also took part in the early stage of this venopathy pathogenesis, evident by the up-regulated mitochondrial transcription factor A and mitochondrial DNA polymerase γ in venous SMCs. In conclusion, synergistic effects of fluid shear stress and high phosphate induce venous SMC osteogenesis via the ERK1/2 pathway through activating the mechanosensing integrin β1 signaling. The present study identified a promising druggable target for reducing AVF calcification, which deserves further in vivo investigations.

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

Role of Vascular Smooth Muscle Cell Phenotype Switching in Arteriogenesis

Arteriogenesis is one of the primary physiological means by which the circulatory collateral system restores blood flow after significant arterial occlusion in peripheral arterial disease patients. Vascular smooth muscle cells (VSMCs) are the predominant cell type in collateral arteries and respond to altered blood flow and inflammatory conditions after an arterial occlusion by switching their phenotype between quiescent contractile and proliferative synthetic states. Maintaining the contractile state of VSMC is required for collateral vascular function to regulate blood vessel tone and blood flow during arteriogenesis, whereas synthetic SMCs are crucial in the growth and remodeling of the collateral media layer to establish more stable conduit arteries. Timely VSMC phenotype switching requires a set of coordinated actions of molecular and cellular mediators to result in an expansive remodeling of collaterals that restores the blood flow effectively into downstream ischemic tissues. This review overviews the role of VSMC phenotypic switching in the physiological arteriogenesis process and how the VSMC phenotype is affected by the primary triggers of arteriogenesis such as blood flow hemodynamic forces and inflammation. Better understanding the role of VSMC phenotype switching during arteriogenesis can identify novel therapeutic strategies to enhance revascularization in peripheral arterial disease.

Brusatol-Enriched Brucea javanica Oil Ameliorated Dextran Sulfate Sodium-Induced Colitis in Mice: Involvement of NF-κB and RhoA/ROCK Signaling Pathways

Brucea javanica oil (BJO) is beneficial for the treatment of ulcerative colitis (UC), and that quassinoids in particular brusatol are bioactive components. However, it is still uncertain whether or not other components in BJO, such as oleic acid and fatty acids, have an anti-UC effect. The present study is aimed at comparing the anti-UC effects between brusatol-enriched BJO (BE-BJO) and brusatol-free BJO (BF-BJO) and at exploring the effects and mechanisms of BE-BJO on colon inflammation and intestinal epithelial barrier function. Balb/C mice received 3% (wt/vol) DSS for one week to establish the UC model. Different doses of BE-BJO, BF-BJO, or BJO were treated. The result illustrated that BE-BJO alleviated DSS-induced loss of body weight, an increase of disease activity index (DAI), and a shortening of colon, whereas BF-BJO did not have these protective effects. BE-BJO treatment improved the morphology of colon tissue, inhibited the production and release of TNF-α, IFN-γ, IL-6, and IL-1β in the colon tissue, and reversed the decreased expressions of ZO-1, occludin, claudin-1, and E-cadherin induced by DSS but augmented claudin-2 expression. Mechanistically, BE-BJO repressed phosphorylation of NF-κB subunit p65, suppressed RhoA activation, downregulated ROCK, and prevented phosphorylation of myosin light chain (MLC) in DSS-treated mice, indicating that the protective effect of BE-BJO is attributed to suppression of NF-κB and RhoA/ROCK signaling pathways. These findings confirm that brusatol is an active component from BJO in the treatment of UC.

New susceptibility alleles associated with severe coronary artery stenosis in the Lebanese population

BACKGROUND

Coronary Artery Disease (CAD) is the narrowing or blockage of the coronary arteries. It is closely associated with numerous genetics and environmental factors that have been extensively evaluated in various populations. In recent studies, severe phenotypes have been strongly linked to genetic risk factors.

METHODS

This study investigated the association of clinical, demographic, and genetic factors with severe coronary artery stenosis phenotypes in our population composed of 1734 individuals with severe coronary stenosis (≥ 50% in coronary vessels) and comparing them to 757 controls with no evidence of stenosis on angiography. We performed generalized linear model (GLM) genome-wide association studies to evaluate three stratification models and their associations to characteristics of the clinical disease. In model 1, patients were not stratified. In model 2, patients were stratified based on presence or absence of CAD family history (FxCAD). In model 3, patients were stratified by young age of CAD onset.

RESULTS

Eight SNPs (single nucleotide polymorphism) were significantly associated with severe CAD phenotypes in the various models [Formula: see text], four of these SNPs were associated with severe CAD and the four others were specifically significant for young CAD patients. While these SNPs were not previously reported for association with CAD, six of them are present in genes that have already been linked to coronary disease.

CONCLUSION

In conclusion, this study presents new genetic factors associated with severe stenosis and highlights different risk factors associated with a young age at diagnosis of CAD.

Advancing tissue-engineered vascular grafts via their endothelialization and mechanical conditioning

Tissue engineering has garnered significant attention for its potential to address the predominant modes of failure of small diameter vascular prostheses, namely mid-graft thrombosis and anastomotic intimal hyperplasia. In this review, we described two main features underpinning the promise of tissue-engineered vascular grafts: the incorporation of an antithrombogenic endothelium, and the generation of a structurally and biomechanically mimetic extracellular matrix. From the early attempts at the in-vitro endothelialization of vascular prostheses in the 1970s through to the ongoing clinical trials of fully tissue-engineered vascular grafts, the historical advancements and unresolved challenges that characterize the current state-of-the-art are summarized in a manner that establishes a guide for the development of an effective vascular prosthesis for small diameter arterial reconstruction. The importance of endothelial cell purity and their arterial specification for the prevention of both diffuse neointimal hyperplasia and the accelerated development of atherosclerotic lesions is delineated. Additionally, the need for an extracellular matrix that recapitulates both the composition and structure of native elastic arteries to facilitate the protracted stability and patency of an engineered vasoactive conduit is described. Finally, the capacity of alternative sources of cells and mechanical conditioning to overcome these technical barriers to the clinical translation of an effective small diameter vascular prosthesis is discussed. In conclusion, this review provides an overview of the historical development of tissue-engineered vascular grafts, highlighting specific areas warranting further research, and commentating on the outlook of a clinically feasible and therapeutically efficacious vascular prosthesis for small diameter arterial reconstruction.

LncRNA-SMILR modulates RhoA/ROCK signaling by targeting miR-141 to regulate vascular remodeling in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a fatal progressive disease characterized by an increased blood pressure in the pulmonary arteries. RhoA/Rho-kinase (RhoA/ROCK) signaling activation is often associated with PAH. The purpose of this study is to investigate the role and mechanisms of long noncoding RNA (lncRNA) smooth muscle-induced lncRNA (SMILR) to activate the RhoA/ROCK pathway in PAH. SMILR, microRNA-141 (miR-141), and RhoA were identified by qRT-PCR in PAH patients' serum. 3-(4,5-Dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT), wound-healing assay, cell counting kit-8 (CCK-8) assay, and flow cytometry were performed to determine cell viability, migration, proliferation, and cell cycle in human pulmonary arterial smooth muscle cells (hPASMCs) and primary PASMCs from PAH patients. We also performed bioinformatical prediction, luciferase reporter assay, and RNA-binding protein immunoprecipitation (RIP) to assess the interaction among SMILR, miR-141, and RhoA. The RhoA/ROCK pathway and proliferation-related proteins were measured by Western blotting. Finally, we introduced the small hairpin (sh)SMILR to monocrotaline-induced PAH rat model and used the hemodynamic measurement, qRT-PCR, and immunohistochemistry to examine the therapeutic effects of shSMILR. SMILR and RhoA expression were upregulated, while miR-141 expression was downregulated in PAH patients. SMILR directly interacted with miR-141 and negatively regulated its expression. Knockdown of SMILR suppressed PASMC proliferation and migration induced by hypoxia. Furthermore, overexpression of miR-141 could inhibit the RhoA/ROCK pathway by binding to RhoA, thereby repressing cell proliferation-related signals. Knockdown of SMILR significantly inhibited the Rho/ROCK activation and vascular remodeling in monocrotaline-induced rats. Knockdown of SMILR effectively elevated miR-141 expression and in turn inhibited the RhoA/ROCK pathway to regulate vascular remodeling and reduce blood pressure in PAH.NEW & NOTEWORTHY Smooth muscle enriched long noncoding RNA (SMILR), as a long noncoding RNA (lncRNA), was increased in pulmonary arterial hypertension (PAH) patients and in vitro and in vivo models. SMILR activated RhoA/ROCK signaling by targeting miR-141 to disinhibit its downstream target RhoA. SMILR knockdown or miR-141 overexpression inhibited hypoxia-induced cell proliferation and migration via repressing RhoA/ROCK signaling in pulmonary arterial smooth muscle cells (PASMCs), which was confirmed in vivo experiments that knockdown of SMILR inhibited vascular remodeling and alleviated PAH in rats. SMILR may be a promising and novel therapeutic target for the treatment and drug development of PAH.

Engineering blood vessels and vascularized tissues: technology trends and potential clinical applications

Vascular tissue engineering has the potential to make a significant impact on the treatment of a wide variety of medical conditions, including providing in vitro generated vascularized tissue and organ constructs for transplantation. Since the first report on the construction of a biological blood vessel, significant research and technological advances have led to the generation of clinically relevant large and small diameter tissue engineered vascular grafts (TEVGs). However, developing a biocompatible blood-contacting surface is still a major challenge. Researchers are using biomimicry to generate functional vascular grafts and vascular networks. A multi-disciplinary approach is being used that includes biomaterials, cells, pro-angiogenic factors and microfabrication technologies. Techniques to achieve spatiotemporal control of vascularization include use of topographical engineering and controlled-release of growth/pro-angiogenic factors. Use of decellularized natural scaffolds has gained popularity for engineering complex vascularized organs for potential clinical use. Pre-vascularization of constructs prior to implantation has also been shown to enhance its anastomosis after implantation. Host-implant anastomosis is a phenomenon that is still not fully understood. However, it will be a critical factor in determining the in vivo success of a TEVGs or bioengineered organ. Many clinical studies have been conducted using TEVGs, but vascularized tissue/organ constructs are still in the research & development stage. In addition to technical challenges, there are commercialization and regulatory challenges that need to be addressed. In this review we examine recent advances in the field of vascular tissue engineering, with a focus on technology trends, challenges and potential clinical applications.

Novel cone-and-plate flow chamber with controlled distribution of wall fluid shear stress

Fluid flow in blood vessels or interstitial fluid flow within tissue cavities plays important roles in tissue regeneration. One of the fundamental issues for in vitro study of the effects of fluid shear stress (FSS) on cells is the development of a flow chamber that can provide a controlled FSS field. In this study, we developed a novel cone-and-plate flow chamber based on viscometry technology, in which the cone's shape was optimized to produce a uniform wall FSS field on the surface of a standard six-well cell culture plate. By using a FSS finite element method, the effects of different geometric parameters of cone and plate, viscosity coefficient of fluid, and angular velocity on wall FSS at the bottom surface of the culture plate were investigated. Results of the simulation demonstrated that the cone with polyline or truncated generatrix (TG) could produce wall FSS as high as 1 or 2 Pa with uniform distribution, in which the area of the identical region for the cone with TG accounts for more than 69% of the total area. In addition, with the cone in close proximity to the plate surface, a gap distance of 0.1 mm can produce a uniform FSS field with a magnitude as high as 2 Pa over the majority of the plate. Furthermore, particle image velocimetry was utilized to measure the distribution of wall FSS, through which the numerical simulation results were experimentally demonstrated. This study presents a powerful new device for in vitro fluid flow loading at the cellular level.

MicroRNA-21 increases the expression level of occludin through regulating ROCK1 in prevention of intestinal barrier dysfunction

OBJECTIVE

The aim of this study is to investigate the role of molecular mechanism of microRNA (miR)-21 on tight junction (TJ)-proteins and its protective effects on the intestinal barrier.

METHODS

TJ proteins and target genes expression were analyzed in miR-21 inhibition and overexpression NCM460 cell lines. To further verify the role of miR-21, the mmu-miR-21 intestinal epithelial conditional knockout (IKO) mice model was established. MiR-21 expression was detected in clinical specimens of acute stercoral obstruction patients.

RESULTS

Rho-associated protein kinase 1 (ROCK1) were identified as target genes of miR-21. There is a negative correlation between miR-21 expression level and TJ proteins levels. TJ protein and ROCK1 were significantly decreased in miR-21 IKO mice, which presented intestinal inflammation response and intestinal barrier dysfunction (both P < 0.05). Determination of clinical samples showed consistent results with NCM460 cell line and miR-21 IKO mice.

CONCLUSIONS

MiR-21 could be a protective factor of intestinal barrier dysfunction, which promoting the expression of TJ protein by targeting ROCK1 in vivo and in vitro.

Vascular Tissue Engineering: Progress, Challenges, and Clinical Promise

Although the clinical demand for bioengineered blood vessels continues to rise, current options for vascular conduits remain limited. The synergistic combination of emerging advances in tissue fabrication and stem cell engineering promises new strategies for engineering autologous blood vessels that recapitulate not only the mechanical properties of native vessels but also their biological function. Here we explore recent bioengineering advances in creating functional blood macro and microvessels, particularly featuring stem cells as a seed source. We also highlight progress in integrating engineered vascular tissues with the host after implantation as well as the exciting pre-clinical and clinical applications of this technology.