High-throughput identification of small molecules that affect human embryonic vascular development

Cracking the code of the cardiovascular enigma: hPSC-derived endothelial cells unveil the secrets of endothelial dysfunction

Endothelial dysfunction is a central contributor to the development of most cardiovascular diseases and is characterised by the reduced synthesis or bioavailability of the vasodilator nitric oxide together with other abnormalities such as inflammation, senescence, and oxidative stress. The use of patient-specific and genome-edited human pluripotent stem cell-derived endothelial cells (hPSC-ECs) has shed novel insights into the role of endothelial dysfunction in cardiovascular diseases with strong genetic components such as genetic cardiomyopathies and pulmonary arterial hypertension. However, their utility in studying complex multifactorial diseases such as atherosclerosis, metabolic syndrome and heart failure poses notable challenges. In this review, we provide an overview of the different methods used to generate and characterise hPSC-ECs before comprehensively assessing their effectiveness in cardiovascular disease modelling and high-throughput drug screening. Furthermore, we explore current obstacles that will need to be overcome to unleash the full potential of hPSC-ECs in facilitating patient-specific precision medicine. Addressing these challenges holds great promise in advancing our understanding of intricate cardiovascular diseases and in tailoring personalised therapeutic strategies.

Applications, Challenges, and Prospects of Induced Pluripotent Stem Cells for Vascular Disease

Vascular disease, including heart disease, stroke, and peripheral arterial disease, is one of the leading causes of death and disability and represents a significant global health issue. Since the development of human induced pluripotent stem cells (hiPSCs) in 2007, hiPSCs have provided unique and tremendous opportunities for studying human pathophysiology, disease modeling, and drug discovery in the field of regenerative medicine. In this review, we discuss vascular physiology and related diseases, the current methods for generating vascular cells (e.g., endothelial cells, smooth muscle cells, and pericytes) from hiPSCs, and describe the opportunities and challenges to the clinical applications of vascular organoids, tissue-engineered blood vessels, and vessels-on-a-chip. We then explore how hiPSCs can be used to study and treat inherited vascular diseases and discuss the current challenges and future prospects. In the future, it will be essential to develop vascularized organoids or tissues that can simultaneously undergo shear stress and cyclic stretching. This development will not only increase their maturity and function but also enable effective and innovative disease modeling and drug discovery.

Advances in the differentiation of pluripotent stem cells into vascular cells

Blood vessels constitute a closed pipe system distributed throughout the body, transporting blood from the heart to other organs and delivering metabolic waste products back to the lungs and kidneys. Changes in blood vessels are related to many disorders like stroke, myocardial infarction, aneurysm, and diabetes, which are important causes of death worldwide. Translational research for new approaches to disease modeling and effective treatment is needed due to the huge socio-economic burden on healthcare systems. Although mice or rats have been widely used, applying data from animal studies to human-specific vascular physiology and pathology is difficult. The rise of induced pluripotent stem cells (iPSCs) provides a reliable in vitro resource for disease modeling, regenerative medicine, and drug discovery because they carry all human genetic information and have the ability to directionally differentiate into any type of human cells. This review summarizes the latest progress from the establishment of iPSCs, the strategies for differentiating iPSCs into vascular cells, and the in vivo transplantation of these vascular derivatives. It also introduces the application of these technologies in disease modeling, drug screening, and regenerative medicine. Additionally, the application of high-tech tools, such as omics analysis and high-throughput sequencing, in this field is reviewed.

Identification of side effects of COVID-19 drug candidates on embryogenesis using an integrated zebrafish screening platform

Drug repurposing is an important strategy in COVID-19 treatment, but many clinically approved compounds have not been extensively studied in the context of embryogenesis, thus limiting their administration during pregnancy. Here we used the zebrafish embryo model organism to test the effects of 162 marketed drugs on cardiovascular development. Among the compounds used in the clinic for COVD-19 treatment, we found that Remdesivir led to reduced body size and heart functionality at clinically relevant doses. Ritonavir and Baricitinib showed reduced heart functionality and Molnupiravir and Baricitinib showed effects on embryo activity. Sabizabulin was highly toxic at concentrations only 5 times higher than Cmax and led to a mean mortality of 20% at Cmax. Furthermore, we tested if zebrafish could be used as a model to study inflammatory response in response to spike protein treatment and found that Remdesivir, Ritonavir, Molnupiravir, Baricitinib as well as Sabizabulin counteracted the inflammatory response related gene expression upon SARS-CoV-2 spike protein treatment. Our results show that the zebrafish allows to study immune-modulating properties of COVID-19 compounds and highlights the need to rule out secondary defects of compound treatment on embryogenesis. All results are available on a user friendly web-interface https://share.streamlit.io/alernst/covasc_dataapp/main/CoVasc_DataApp.py that provides a comprehensive overview of all observed phenotypic effects and allows personalized search on specific compounds or group of compounds. Furthermore, the presented platform can be expanded for rapid detection of developmental side effects of new compounds for treatment of COVID-19 and further viral infectious diseases.

Predicting Prenatal Developmental Toxicity Based On the Combination of Chemical Structures and Biological Data

For hazard identification, classification, and labeling purposes, animal testing guidelines are required by law to evaluate the developmental toxicity potential of new and existing chemical products. However, guideline developmental toxicity studies are costly, time-consuming, and require many laboratory animals. Computational modeling has emerged as a promising, animal-sparing, and cost-effective method for evaluating the developmental toxicity potential of chemicals, such as endocrine disruptors, without the use of animals. We aimed to develop a predictive and explainable computational model for developmental toxicants. To this end, a comprehensive dataset of 1244 chemicals with developmental toxicity classifications was curated from public repositories and literature sources. Data from 2140 toxicological high-throughput screening assays were extracted from PubChem and the ToxCast program for this dataset and combined with information about 834 chemical fragments to group assays based on their chemical-mechanistic relationships. This effort revealed two assay clusters containing 83 and 76 assays, respectively, with high positive predictive rates for developmental toxicants identified with animal testing guidelines (PPV = 72.4 and 77.3% during cross-validation). These two assay clusters can be used as developmental toxicity models and were applied to predict new chemicals for external validation. This study provides a new strategy for constructing alternative chemical developmental toxicity evaluations that can be replicated for other toxicity modeling studies.

Human Engineered Heart Tissue Models for Disease Modeling and Drug Discovery

The emergence of human induced pluripotent stem cells (hiPSCs) and efficient differentiation of hiPSC-derived cardiomyocytes (hiPSC-CMs) induced from diseased donors have the potential to recapitulate the molecular and functional features of the human heart. Although the immaturity of hiPSC-CMs, including the structure, gene expression, conduct, ion channel density, and Ca²⁺ kinetics, is a major challenge, various attempts to promote maturation have been effective. Three-dimensional cardiac models using hiPSC-CMs have achieved these functional and morphological maturations, and disease models using patient-specific hiPSC-CMs have furthered our understanding of the underlying mechanisms and effective therapies for diseases. Aside from the mechanisms of diseases and drug responses, hiPSC-CMs also have the potential to evaluate the safety and efficacy of drugs in a human context before a candidate drug enters the market and many phases of clinical trials. In fact, novel drug testing paradigms have suggested that these cells can be used to better predict the proarrhythmic risk of candidate drugs. In this review, we overview the current strategies of human engineered heart tissue models with a focus on major cardiac diseases and discuss perspectives and future directions for the real application of hiPSC-CMs and human engineered heart tissue for disease modeling, drug development, clinical trials, and cardiotoxicity tests.

Potency and selectivity indices of Myristica fragrans Houtt. mace chloroform extract against non-clinical and clinical human pathogens

This study assessed the antimicrobial, toxicity, and phytochemical profiles of Myristica fragrans extracts. Different solvent extracts were tested for antimicrobial activity against clinical and reference microbial strains, using disc and well diffusion assays and microdilution techniques. Antioxidant potential was investigated using 2,2-diphenyl-1-picryhydrazyl (DPPH) assays. Cytotoxicity assay was conducted against human umbilical vein endothelial cells (HUVECs) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Acute toxicity was assessed in laboratory Swiss albino mice at a single dose of 2,000 mg/kg body weight for 14 days. To assess the phytochemical constituents, spectrophotometric and gas chromatography-mass spectrometry (GC-MS) methods were used. The chloroform extract revealed antimicrobial potencies against the Gram-positive bacteria and C. albicans with minimum inhibitory concentrations. In the DPPH assay, the IC50 value of the chloroform extract was determined to be 1.49 mg/mL. The phenolic and flavonoid contents were 26.64 ±  0.1 mg of gallic acid equivalents/g and 8.28  ± 0.1 mg quercetin equivalents/g, respectively. The IC50 value was determined to be 49 µg/mL against the HUVEC line. No mortality or morbidity was observed. GC-MS analysis indicated the presence of 2-cyclopenten-1-one (44.72%) as a major compound. The current results provide scientific support for the use of M. fragrans in folk medicine.

Nuisance compounds in cellular assays

Compounds that exhibit assay interference or undesirable mechanisms of bioactivity ("nuisance compounds") are routinely encountered in cellular assays, including phenotypic and high-content screening assays. Much is known regarding compound-dependent assay interferences in cell-free assays. However, despite the essential role of cellular assays in chemical biology and drug discovery, there is considerably less known about nuisance compounds in more complex cell-based assays. In our view, a major obstacle to realizing the full potential of chemical biology will not just be difficult-to-drug targets or even the sheer number of targets, but rather nuisance compounds, due to their ability to waste significant resources and erode scientific trust. In this review, we summarize our collective academic, government, and industry experiences regarding cellular nuisance compounds. We describe assay design strategies to mitigate the impact of nuisance compounds and suggest best practices to efficiently address these compounds in complex biological settings.

Human iPSC modeling of heart disease for drug development

Human induced pluripotent stem cells (hiPSCs) have emerged as a promising platform for pharmacogenomics and drug development. In cardiology, they make it possible to produce unlimited numbers of patient-specific human cells that reproduce hallmark features of heart disease in the culture dish. Their potential applications include the discovery of mechanism-specific therapeutics, the evaluation of safety and efficacy in a human context before a drug candidate reaches patients, and the stratification of patients for clinical trials. Although this new technology has the potential to revolutionize drug discovery, translational hurdles have hindered its widespread adoption for pharmaceutical development. Here we discuss recent progress in overcoming these hurdles that should facilitate the use of hiPSCs to develop new medicines and individualize therapies for heart disease.

Induced pluripotent stem cell-derived vascular networks to screen nano-bio interactions

The vascular bioactivity/safety of nanomaterials is typically evaluated by animal testing, which is of low throughput and does not account for biological differences between animals and humans such as ageing, metabolism and disease profiles. The development of personalized human in vitro platforms to evaluate the interaction of nanomaterials with the vascular system would be important for both therapeutic and regenerative medicine. A library of 30 nanoparticle (NP) formulations, in use in imaging, antimicrobial and pharmaceutical applications, was evaluated in a reporter zebrafish model of vasculogenesis and then tested in personalized humanized models composed of human-induced pluripotent stem cell (hiPSC)-derived endothelial cells (ECs) with "young" and "aged" phenotypes in 3 vascular network formats: 2D (in polystyrene dish), 3D (in Matrigel) and in a blood vessel on a chip. As a proof of concept, vascular toxicity was used as the main readout. The results show that the toxicity profile of NPs to hiPSC-ECs was dependent on the "age" of the endothelial cells and vascular network format. hiPSC-ECs were less susceptible to the cytotoxicity effect of NPs when cultured in flow than in static conditions, the protective effect being mediated, at least in part, by glycocalyx. Overall, the results presented here highlight the relevance of in vitro hiPSC-derived vascular systems to screen vascular nanomaterial interactions.

Development and Application of Endothelial Cells Derived From Pluripotent Stem Cells in Microphysiological Systems Models

The vascular endothelium is present in all organs and blood vessels, facilitates the exchange of nutrients and waste throughout different organ systems in the body, and sets the tone for healthy vessel function. Mechanosensitive in nature, the endothelium responds to the magnitude and temporal waveform of shear stress in the vessels. Endothelial dysfunction can lead to atherosclerosis and other diseases. Modeling endothelial function and dysfunction in organ systems in vitro, such as the blood–brain barrier and tissue-engineered blood vessels, requires sourcing endothelial cells (ECs) for these biomedical engineering applications. It can be difficult to source primary, easily renewable ECs that possess the function or dysfunction in question. In contrast, human pluripotent stem cells (hPSCs) can be sourced from donors of interest and renewed almost indefinitely. In this review, we highlight how knowledge of vascular EC development in vivo is used to differentiate induced pluripotent stem cells (iPSC) into ECs. We then describe how iPSC-derived ECs are being used currently in in vitro models of organ function and disease and in vivo applications.

Advancing human induced pluripotent stem cell-derived blood-brain barrier models for studying immune cell interactions

Human induced pluripotent stem cell (hiPSC)‐derived blood‐brain barrier (BBB) models established to date lack expression of key adhesion molecules involved in immune cell migration across the BBB in vivo. Here, we introduce the extended endothelial cell culture method (EECM), which differentiates hiPSC‐derived endothelial progenitor cells to brain microvascular endothelial cell (BMEC)‐like cells with good barrier properties and mature tight junctions. Importantly, EECM‐BMEC‐like cells exhibited constitutive cell surface expression of ICAM‐1, ICAM‐2, and E‐selectin. Pro‐inflammatory cytokine stimulation increased the cell surface expression of ICAM‐1 and induced cell surface expression of P‐selectin and VCAM‐1. Co‐culture of EECM‐BMEC‐like cells with hiPSC‐derived smooth muscle‐like cells or their conditioned medium further increased the induction of VCAM‐1. Functional expression of endothelial ICAM‐1 and VCAM‐1 was confirmed by T‐cell interaction with EECM‐BMEC‐like cells. Taken together, we introduce the first hiPSC‐derived BBB model that displays an adhesion molecule phenotype that is suitable for the study of immune cell interactions.

Flow-Induced Transcriptomic Remodeling of Endothelial Cells Derived From Human Induced Pluripotent Stem Cells

The vascular system is essential for the development and function of all organs and tissues in our body. The molecular signature and phenotype of endothelial cells (EC) are greatly affected by blood flow-induced shear stress, which is a vital component of vascular development and homeostasis. Recent advances in differentiation of ECs from human induced pluripotent stem cells (hiPSC) have enabled development of in vitro experimental models of the vasculature containing cells from healthy individuals or from patients harboring genetic variants or diseases of interest. Here we have used hiPSC-derived ECs and bulk- and single-cell RNA sequencing to study the effect of flow on the transcriptomic landscape of hiPSC-ECs and their heterogeneity. We demonstrate that hiPS-ECs are plastic and they adapt to flow by expressing known flow-induced genes. Single-cell RNA sequencing showed that flow induced a more homogenous and homeostatically more stable EC population compared to static cultures, as genes related to cell polarization, barrier formation and glucose and fatty acid transport were induced. The hiPS-ECs increased both arterial and venous markers when exposed to flow. Interestingly, while in general there was a greater increase in the venous markers, one cluster with more arterial-like hiPS-ECs was detected. Single-cell RNA sequencing revealed that not all hiPS-ECs are similar even after sorting, but exposing them to flow increases their homogeneity. Since hiPS-ECs resemble immature ECs and demonstrate high plasticity in response to flow, they provide an excellent model to study vascular development.

Adverse effect of cylindrospermopsin on embryonic development in zebrafish (Danio rerio)

Eutrophication of freshwater bodies increases the occurrence of toxic cyanobacterial blooms. The cyanobacterial toxin cylindrospermopsin (CYN) is receiving great interest due to its increasing presence in waterbodies. However, the toxic effects of CYN on zebrafish development are poorly understood, especially the toxicological mechanism, which is still unclear. In this study, we examined the adverse effects of CYN on embryonic development in zebrafish. CYN (2-2000 nM) exposure decreased embryos survival rate, hatching rate, body length and eye size in a concentration-dependent manner and caused abnormalities in embryo morphology, including pericardial edema, spinal curvature, tail deformity, uninflated swim bladder, cardiac and vascular defects. CYN at concentrations of 20 nM or higher significantly increased ROS level and promoted cell apoptosis in zebrafish embryos. To preliminarily elucidate the potential mechanism of zebrafish developmental toxicity caused by CYN, we examined the expression of oxidative stress- and apoptotic-related genes. CYN could promote the expression of oxidative stress-related genes (SOD1, CAT and GPx1) and induce changes in transcriptional levels of apoptotic-related genes (p53, Bax and Bcl-2). Taken together, CYN induced adverse effects on zebrafish embryos development, which may associate with oxidative stress and apoptosis. These outcomes will advance our understanding of CYN toxicity, environmental problems and health hazards caused by climate changes and eutrophication.

Co-culture of human induced pluripotent stem cell-derived retinal pigment epithelial cells and endothelial cells on double collagen-coated honeycomb films

In vitro cell culture models representing the physiological and pathological features of the outer retina are urgently needed. Artificial tissue replacements for patients suffering from degenerative retinal diseases are similarly in great demand. Here, we developed a co-culture system based solely on the use of human induced pluripotent stem cell (hiPSC)-derived cells. For the first time, hiPSC-derived retinal pigment epithelium (RPE) and endothelial cells (EC) were cultured on opposite sides of porous polylactide substrates prepared by breath figures (BF), where both surfaces had been collagen-coated by Langmuir-Schaefer (LS) technology. Small modifications of casting conditions during material preparation allowed the production of free-standing materials with distinct porosity, wettability and ion diffusion capacity. Complete pore coverage was achieved by the collagen coating procedure, resulting in a detectable nanoscale topography. Primary retinal endothelial cells (ACBRI181) and umbilical cord vein endothelial cells (hUVEC) were utilised as EC references. Mono-cultures of all ECs were prepared for comparison. All tested materials supported cell attachment and growth. In mono-culture, properties of the materials had a major effect on the growth of all ECs. In co-culture, the presence of hiPSC-RPE affected the primary ECs more significantly than hiPSC-EC. In consistency, hiPSC-RPE were also less affected by hiPSC-EC than by the primary ECs. Finally, our results show that the modulation of the porosity of the materials can promote or prevent EC migration. In short, we showed that the behaviour of the cells is highly dependent on the three main variables of the study: the presence of a second cell type in co-culture, the source of endothelial cells and the biomaterial properties. The combination of BF and LS methodologies is a powerful strategy to develop thin but stable materials enabling cell growth and modulation of cell-cell contact. STATEMENT OF SIGNIFICANCE: Artificial blood-retinal barriers (BRB), mimicking the interface at the back of the eye, are urgently needed as physiological and disease models, and for tissue transplantation targeting patients suffering from degenerative retinal diseases. Here, we developed a new co-culture model based on thin, biodegradable porous films, coated on both sides with collagen, one of the main components of the natural BRB, and cultivated endothelial and retinal pigment epithelial cells on opposite sides of the films, forming a three-layer structure. Importantly, our hiPSC-EC and hiPSC-RPE co-culture model is the first to exclusively use human induced pluripotent stem cells as cell source, which have been widely regarded as an practical candidate for therapeutic applications in regenerative medicine.

A High-Throughput Screening Method to Identify Compounds Displaying Human Vascular Embryonic Toxicity

This article describes a screening platform to identify compounds that affect human embryonic vascular development. The procedure comprises the generation of human embryonic-like endothelial cells (ECs) from human pluripotent stem cells (hPSCs) and subsequent maturation under arterial flow conditions; the use of these cells for the high-throughput screening of small molecules that specifically inhibit the survival of embryonic-like ECs; the confirmation of the hits in embryonic-like ECs cultured under flow shear stress; and final validation in mouse embryonic ECs. The embryonic-like ECs express embryonic genes including DLL1, EPHB2, LYN, TEK, ID1, NRP2, CAST, FLT1, IGF1, DKK3, NIN, LEF1, and SORBS3. The entire screening procedure (without the validation step) can be completed within 1 month. This platform is an alternative/complement to standard animal protocols for assessing the effects of chemicals on embryonic vascular development. © 2019 by John Wiley & Sons, Inc.

Microengineered human amniotic ectoderm tissue array for high-content developmental phenotyping

During early post-implantation human embryogenesis, the epiblast (EPI) within the blastocyst polarizes to generate a cyst with a central lumen. Cells at the uterine pole of the EPI cyst then undergo differentiation to form the amniotic ectoderm (AM), a tissue essential for further embryonic development. While the causes of early pregnancy failure are complex, improper lumenogenesis or amniogenesis of the EPI represent possible contributing factors. Here we report a novel AM microtissue array platform that allows quantitative phenotyping of lumenogenesis and amniogenesis of the EPI and demonstrate its potential application for embryonic toxicity profiling. Specifically, a human pluripotent stem cell (hPSC)-based amniogenic differentiation protocol was developed using a two-step micropatterning technique to generate a regular AM microtissue array with defined tissue sizes. A computer-assisted analysis pipeline was developed to automatically process imaging data and quantify morphological and biological features of AM microtissues. Analysis of the effects of cell density, cyst size and culture conditions revealed a clear connection between cyst size and amniogenesis of hPSC. Using this platform, we demonstrated that pharmacological inhibition of ROCK signaling, an essential mechanotransductive pathway, suppressed lumenogenesis but did not perturb amniogenic differentiation of hPSC, suggesting uncoupled regulatory mechanisms for AM morphogenesis vs. cytodifferentiation. The AM microtissue array was further applied to screen a panel of clinically relevant drugs, which successfully detected their differential teratogenecity. This work provides a technological platform for toxicological screening of clinically relevant drugs for their effects on lumenogenesis and amniogenesis during early human peri-implantation development, processes that have been previously inaccessible to study.

Generation of Endothelial Cells From Human Pluripotent Stem Cells

Endothelial cells (ECs) are critical for several aspects of cardiovascular disease therapy, including vascular regeneration, personalized drug development, and tissue engineering. Human pluripotent stem cells (hPSCs) afford us with an unprecedented opportunity to produce virtually unlimited quantities of human ECs. In this review, we highlight key developments and outstanding challenges in our ability to derive ECs de novo from hPSCs. Furthermore, we consider strategies for recapitulating the vessel- and tissue-specific functional heterogeneity of ECs in vitro. Finally, we discuss ongoing attempts to utilize hPSC-derived ECs and their progenitors for various therapeutic applications. Continued progress in generating hPSC-derived ECs will profoundly enhance our ability to discover novel drug targets, revascularize ischemic tissues, and engineer clinically relevant tissue constructs. Visual Overview- An online visual overview is available for this article.

Functional characterization of iPSC-derived arterial- and venous-like endothelial cells

The current work reports the functional characterization of human induced pluripotent stem cells (iPSCs)- arterial and venous-like endothelial cells (ECs), derived in chemically defined conditions, either in monoculture or seeded in a scaffold with mechanical properties similar to blood vessels. iPSC-derived arterial- and venous-like endothelial cells were obtained in two steps: differentiation of iPSCs into endothelial precursor cells (CD31^pos/KDR^pos/VE-Cad^med/EphB2^neg/COUP-TF^neg) followed by their differentiation into arterial and venous-like ECs using a high and low vascular endothelial growth factor (VEGF) concentration. Cells were characterized at gene, protein and functional levels. Functionally, both arterial and venous-like iPSC-derived ECs responded to vasoactive agonists such as thrombin and prostaglandin E2 (PGE₂), similar to somatic ECs; however, arterial-like iPSC-derived ECs produced higher nitric oxide (NO) and elongation to shear stress than venous-like iPSC-derived ECs. Both cells adhered, proliferated and prevented platelet activation when seeded in poly(caprolactone) scaffolds. Interestingly, both iPSC-derived ECs cultured in monoculture or in a scaffold showed a different inflammatory profile than somatic ECs. Although both somatic and iPSC-derived ECs responded to tumor necrosis factor-α (TNF-α) by an increase in the expression of intercellular adhesion molecule 1 (ICAM-1), only somatic ECs showed an upregulation in the expression of E-selectin or vascular cell adhesion molecule 1 (VCAM-1).

Advanced in vitro models of vascular biology: Human induced pluripotent stem cells and organ-on-chip technology

The vascular system is one of the first to develop during embryogenesis and is essential for all organs and tissues in our body to develop and function. It has many essential roles including controlling the absorption, distribution and excretion of compounds and therefore determines the pharmacokinetics of drugs and therapeutics. Vascular homeostasis is under tight physiological control which is essential for maintaining tissues in a healthy state. Consequently, disruption of vascular homeostasis plays an integral role in many disease processes, making cells of the vessel wall attractive targets for therapeutic intervention. Experimental models of blood vessels can therefore contribute significantly to drug development and aid in predicting the biological effects of new drug entities. The increasing availability of human induced pluripotent stem cells (hiPSC) derived from healthy individuals and patients have accelerated advances in developing experimental in vitro models of the vasculature: human endothelial cells (ECs), pericytes and vascular smooth muscle cells (VSMCs), can now be generated with high efficiency from hiPSC and used in 'microfluidic chips' (also known as 'organ-on-chip' technology) as a basis for in vitro models of blood vessels. These near physiological scaffolds allow the controlled integration of fluid flow and three-dimensional (3D) co-cultures with perivascular cells to mimic tissue- or organ-level physiology and dysfunction in vitro. Here, we review recent multidisciplinary developments in these advanced experimental models of blood vessels that combine hiPSC with microfluidic organ-on-chip technology. We provide examples of their utility in various research areas and discuss steps necessary for further integration in biomedical applications so that they can be contribute effectively to the evaluation and development of new drugs and other therapeutics as well as personalized (patient-specific) treatments.

Blockade of vascular endothelial growth factor receptor 2 inhibits intraplaque haemorrhage by normalization of plaque neovessels

BACKGROUND

Plaque angiogenesis is associated with atherosclerotic lesion growth, plaque instability and negative clinical outcome. Plaque angiogenesis is a natural occurring process to fulfil the increasing demand of oxygen and nourishment of the vessel wall. However, inadequate formed, immature plaque neovessels are leaky and cause intraplaque haemorrhage.

OBJECTIVE

Blockade of VEGFR2 normalizes the unbridled process of plaque neovessel formation and induces maturation of nascent vessels resulting in prevention of intraplaque haemorrhage and influx of inflammatory cells into the plaque and subsequently increases plaque stability.

METHODS AND RESULTS

In human carotid and vein graft atherosclerotic lesions, leaky plaque neovessels and intraplaque haemorrhage co-localize with VEGF/VEGFR2 and angiopoietins. Using hypercholesterolaemic ApoE3*Leiden mice that received a donor caval vein interposition in the carotid artery, we demonstrate that atherosclerotic vein graft lesions at t28 are associated with hypoxia, Hif1α and Sdf1 up-regulation. Local VEGF administration results in increased plaque angiogenesis. VEGFR2 blockade in this model results in a significant 44% decrease in intraplaque haemorrhage and 80% less extravasated erythrocytes compared to controls. VEGFR2 blockade in vivo results in a 32% of reduction in vein graft size and more stable lesions with significantly reduced macrophage content (30%), and increased collagen (54%) and smooth muscle cell content (123%). Significant decreased VEGF, angiopoietin-2 and increased Connexin 40 expression levels demonstrate increased plaque neovessel maturation in the vein grafts. VEGFR2 blockade in an aortic ring assay showed increased pericyte coverage of the capillary sprouts.

CONCLUSION

Inhibition of intraplaque haemorrhage by controlling neovessels maturation holds promise to improve plaque stability.

Systems-Wide Approaches in Induced Pluripotent Stem Cell Models

Human induced pluripotent stem cells (iPSCs) provide a renewable supply of patient-specific and tissue-specific cells for cellular and molecular studies of disease mechanisms. Combined with advances in various omics technologies, iPSC models can be used to profile the expression of genes, transcripts, proteins, and metabolites in relevant tissues. In the past 2 years, large panels of iPSC lines have been derived from hundreds of genetically heterogeneous individuals, further enabling genome-wide mapping to identify coexpression networks and elucidate gene regulatory networks. Here, we review recent developments in omics profiling of various molecular phenotypes and the emergence of human iPSCs as a systems biology model of human diseases.

How Surrogate and Chemical Genetics in Model Organisms Can Suggest Therapies for Human Genetic Diseases

Genetic diseases are both inherited and acquired. Many genetic diseases fall under the paradigm of orphan diseases, a disease found in < 1 in 2000 persons. With rapid and cost-effective genome sequencing becoming the norm, many causal mutations for genetic diseases are being rapidly determined. In this regard, model organisms are playing an important role in validating if specific mutations identified in patients drive the observed phenotype. An emerging challenge for model organism researchers is the application of genetic and chemical genetic platforms to discover drug targets and drugs/drug-like molecules for potential treatment options for patients with genetic disease. This review provides an overview of how model organisms have contributed to our understanding of genetic disease, with a focus on the roles of yeast and zebrafish in gene discovery and the identification of compounds that could potentially treat human genetic diseases.

Waterborne exposure to low concentrations of BDE-47 impedes early vascular development in zebrafish embryos/larvae

Polybrominated diphenyl ethers (PBDEs) are persistent flame retardants ubiquitously existing in various environment matrices. In spite of a recent reduction in use according to the phase-out policy, high levels of PBDEs are still found in both environmental and biological samples due to their persistent property and large-scale production over a long history. Developmental toxicity is a major health concern of PBDEs. However, the impact of PBDE exposure on vascular development remains poorly understood. In this study, we investigated the effect of low concentrations of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a predominant PBDE congener, in environmental matrices and biota, on early vascular development using zebrafish. Zebrafish embryos were continuously exposed to waterborne BDE-47 at 0.06, 0.2, 0.6 μM starting from 2 h post-fertilization (hpf). Fluorescent images of vasculatures in Tg(kdrl:eGFP) zebrafish were acquired using a confocal microscope. The results indicated that BDE-47 exposure had no effect on hatching rate, survival, body weight, body length or heart rate in the early stage within 72 hpf, whereas zebrafish exposed to BDE-47 exhibited impairments in the growth of multiple types of blood vessels. The percentage of completed intersegmental vessels (ISV) at 30 hpf decreased in embryos treated with BDE-47 in a dose-dependent fashion. BDE-47 exposure led to a slight decrease in the growth of common cardinal vein (CCV), while dramatically hindered CCV remodeling process reflected by the larger CCV area and wider ventral diameter. BDE-47 exposure significantly reduced sub-intestinal vessels (SIV) area as well as the vascularized yolk area in zebrafish larvae at 72 hpf. In addition, the expression of genes related to vascular growth and remodeling was markedly suppressed in BDE-47-exposed zebrafish. These findings demonstrate the adverse effects of BDE-47 on early vascular development, and confirm the vascular toxicity of PBDEs in vivo. The results indicate that developing vasculature in zebrafish is sensitive to BDE-47 exposure, and may serve as a powerful tool for the assessment of early exposure to PBDEs.

Inflammatory Responses and Barrier Function of Endothelial Cells Derived from Human Induced Pluripotent Stem Cells

Several studies have reported endothelial cell (EC) derivation from human induced pluripotent stem cells (hiPSCs). However, few have explored their functional properties in depth with respect to line-to-line and batch-to-batch variability and how they relate to primary ECs. We therefore carried out accurate characterization of hiPSC-derived ECs (hiPSC-ECs) from multiple (non-integrating) hiPSC lines and compared them with primary ECs in various functional assays, which included barrier function using real-time impedance spectroscopy with an integrated assay of electric wound healing, endothelia-leukocyte interaction under physiological flow to mimic inflammation and angiogenic responses in in vitro and in vivo assays. Overall, we found many similarities but also some important differences between hiPSC-derived and primary ECs. Assessment of vasculogenic responses in vivo showed little difference between primary ECs and hiPSC-ECs with regard to functional blood vessel formation, which may be important in future regenerative medicine applications requiring vascularization.

•

Side-by-side comparison of hiPSC and primary ECs in standardized assays

•

Barrier function and inflammatory responses highly consistent among hiPSC-ECs

•

hiPSC-ECs on differentiation day 10 were similar across independent batches and lines

•

hiPSC-ECs are more limited in stromal cell requirements than primary ECs

iPSCs-based generation of vascular cells: reprogramming approaches and applications

Recent advances in the field of induced pluripotent stem cells (iPSCs) research have opened a new avenue for stem cell-based generation of vascular cells. Based on their growth and differentiation potential, human iPSCs constitute a well-characterized, generally unlimited cell source for the mass generation of lineage- and patient-specific vascular cells without any ethical concerns. Human iPSCs-derived vascular cells are perfectly suited for vascular disease modeling studies because patient-derived iPSCs possess the disease-causing mutation, which might be decisive for full expression of the disease phenotype. The application of vascular cells for autologous cell replacement therapy or vascular engineering derived from immune-compatible iPSCs possesses huge clinical potential, but the large-scale production of vascular-specific lineages for regenerative cell therapies depends on well-defined, highly reproducible culture and differentiation conditions. This review will focus on the different strategies to derive vascular cells from human iPSCs and their applications in regenerative therapy, disease modeling and drug discovery approaches.

Zebrafish as a Model for Drug Screening in Genetic Kidney Diseases

Genetic disorders account for a wide range of renal diseases emerging during childhood and adolescence. Due to the utilization of modern biochemical and biomedical techniques, the number of identified disease-associated genes is increasing rapidly. Modeling of congenital human disease in animals is key to our understanding of the biological mechanism underlying pathological processes and thus developing novel potential treatment options. The zebrafish (Danio rerio) has been established as a versatile small vertebrate organism that is widely used for studying human inherited diseases. Genetic accessibility in combination with elegant experimental methods in zebrafish permit modeling of human genetic diseases and dissecting the perturbation of underlying cellular networks and physiological processes. Beyond its utility for genetic analysis and pathophysiological and mechanistic studies, zebrafish embryos, and larvae are amenable for phenotypic screening approaches employing high-content and high-throughput experiments using automated microscopy. This includes large-scale chemical screening experiments using genetic models for searching for disease-modulating compounds. Phenotype-based approaches of drug discovery have been successfully performed in diverse zebrafish-based screening applications with various phenotypic readouts. As a result, these can lead to the identification of candidate substances that are further examined in preclinical and clinical trials. In this review, we discuss zebrafish models for inherited kidney disease as well as requirements and considerations for the technical realization of drug screening experiments in zebrafish.

Humanity in a Dish: Population Genetics with iPSCs

Induced pluripotent stem cells (iPSCs) are powerful tools for investigating the relationship between genotype and phenotype. Recent publications have described iPSC cohort studies of common genetic variants and their effects on gene expression and cellular phenotypes. These in vitro quantitative trait locus (QTL) studies are the first experiments in a new paradigm with great potential: iPSC-based functional population genetic studies. iPSC collections from large cohorts are currently under development to facilitate the next wave of these studies, which have the potential to discover the effects of common genetic variants on cellular phenotypes and to uncover the molecular basis of common genetic diseases. Here, we describe the recent advances in this developing field, and provide a road map for future in vitro functional population genetic studies and trial-in-a-dish experiments.

Differentiation, Evaluation, and Application of Human Induced Pluripotent Stem Cell-Derived Endothelial Cells

The emergence of induced pluripotent stem cell (iPSC) technology paves the way to generate large numbers of patient-specific endothelial cells (ECs) that can be potentially delivered for regenerative medicine in patients with cardiovascular disease. In the last decade, numerous protocols that differentiate EC from iPSC have been developed by many groups. In this review, we will discuss several common strategies that have been optimized for human iPSC-EC differentiation and subsequent studies that have evaluated the potential of human iPSC-EC as a cell therapy or as a tool in disease modeling. In addition, we will emphasize the importance of using in vivo vessel-forming ability and in vitro clonogenic colony-forming potential as a gold standard with which to evaluate the quality of human iPSC-EC derived from various protocols.

[Leukocyte count of puerperal sows]

147 blood samples of postparturient sows of a secluded housing were taken. The samples were conserved with ACD-solution. The influence of the number and week of the lactation and the health of the sow, determined by puerperal diseases was studied. Hematological values of healthy postparturient sows are: leucocytes 12.6 +/- 2.2 G/l; basophile granulocytes 0.1 +/- 0.1 G/l, eosinophile granulocytes 0.5 +/- 0.4 G/l; banded neutrophile granulocytes 1.3 +/- 0.6 G/l, segmented neutrophile granulocytes 5.2 +/- 1.4 G/l; lymphocytes 5.5 +/- 1.4 G/l, monocytes 0.3 +/- 0.3 G/l. The leucocyte number is lower in the investigated herd compared with quotations in the literature. This is based on the good health conditions in the herd. Changes due to the number and week of the lactation have no clinical relevance. Health status, here described by puerperal diseases is the significant influencing factor of the leucocyte number. The severity of puerperal diseases is significant. Due to puerperal diseases the leucocyte number rises quickly after a short drop about 2 G/l. The number of the neutrophile granulocytes increases, but the lymphocyte number is reduced at the beginning of the illness. The application of ACD-solution for stabilizing of great amounts of blood samples under practical conditions is demonstrated. It is possible to stabilize pigs blood well.