Search

Bone diseases such as osteoporosis, delayed or impaired bone healing, and osteoarthritis still represent a social, financial, and personal burden for affected patients and society. Fully humanized in vitro 3D models of cancellous bone tissue are needed to develop new treatment strategies and meet patient-specific needs. Here, we demonstrate a successful cell-sheet-based process for optimized mesenchymal stromal cell (MSC) seeding on a β-tricalcium phosphate (TCP) scaffold to generate 3D models of cancellous bone tissue. Therefore, we seeded MSCs onto the β-TCP scaffold, induced osteogenic differentiation, and wrapped a single osteogenically induced MSC sheet around the pre-seeded scaffold. Comparing the wrapped with an unwrapped scaffold, we did not detect any differences in cell viability and structural integrity but a higher cell seeding rate with osteoid-like granular structures, an indicator of enhanced calcification. Finally, gene expression analysis showed a reduction in chondrogenic and adipogenic markers, but an increase in osteogenic markers in MSCs seeded on wrapped scaffolds. We conclude from these data that additional wrapping of pre-seeded scaffolds will provide a local niche that enhances osteogenic differentiation while repressing chondrogenic and adipogenic differentiation. This approach will eventually lead to optimized preclinical in vitro 3D models of cancellous bone tissue to develop new treatment strategies. [ABSTRACT FROM AUTHOR]

The cholecystokinin type 2 receptor (CCK2-R) represents an ideal target for cancer therapy since it is overexpressed in several tumors and is associated with poor prognosis. Nastorazepide (Z-360), a selective CCK2-R antagonist, has been widely investigated as a CCK2-R ligand for targeted therapy; however, its high hydrophobicity may represent a limit to cell selectivity and optimal in vivo biodistribution. Here, we present three new fluorescent Z-360 derivatives ( IP-002 G -Rho, IP-002 L -Rho, and IP-002 M -Rho ) in which nastorazepide was linked, through spacers bearing different saccharides (glucose (G), lactose (L), and maltotriose (M)), to sulforhodamine B. A fourth compound ( IP-002 H -Rho ) with no pendant sugar was also synthesized as a control. Through two-dimensional (2D) and three-dimensional (3D) in vitro studies, we evaluated the compound association with and selectivity for CCK2-R-overexpressing cells (A431-CCK2-R + ) vs CCK2-R-underexpressing cells (A431 WT). 2D in vitro studies highlighted a progressive increase of IP-002 x -Rho association with A431-CCK2-R + cells according to the linker hydrophilicity, that is, maltotriose > lactose > glucose > hydrogen, with IP-002 M -Rho showing a 2.4- and a 1.36-fold higher uptake than IP-002 G -Rho and IP-002 L -Rho , respectively. Unexpectedly, IP-002 H -Rho showed a similar cell association to that of IP-002 L -Rho but with no difference between the two tested cell lines. On the contrary, association with A431-CCK2-R + cells as compared to the A431 WT was found to be 1.08-, 1.14-, and 1.37-fold higher for IP-002 G -Rho , IP-002 L -Rho , and IP-002 M -Rho , respectively, proving IP-002 M -Rho to be the best-performing compound, as also confirmed by competition studies. Trafficking studies on A431-CCK2-R + cells incubated with IP-002 M -Rho suggested the coexistence of receptor-mediated endocytosis and simple diffusion. On the contrary, a high and selective uptake of IP-002 M -Rho by A431-CCK2-R + cells only was observed on 3D scaffolds embedded with cells, underlining the importance of 3D models in in vitro preliminary evaluation.

Owing to retained hepatic phenotypes and functions, human three-dimensional (3D) hepatic models established with diverse hepatic cell types are thought to recoup the gaps in drug development and disease modeling limited by a conventional two-dimensional (2D) cell culture system and species-specific variability in drug metabolizing enzymes and transporters. Primary human hepatocytes, human hepatic cancer cell lines, and human stem cell–derived hepatocyte-like cells are three main hepatic cell types used in current models and exhibit divergent hepatic phenotypes. Primary human hepatocytes derived from healthy hepatic parenchyma resemble in vivo–like genetic and metabolic profiling. Human hepatic cancer cell lines are unlimitedly reproducible and tumorigenic. Stem cell–derived hepatocyte-like cells derived from patients are promising to retain the donor’s genetic background. It has been suggested in some studies that unique properties of cell types endue them with benefits in different research fields of in vitro 3D modeling paradigm. For instance, the primary human hepatocyte was thought to be the gold standard for hepatotoxicity study, and stem cell–derived hepatocyte-like cells have taken a main role in personalized medicine and regenerative medicine. However, the comprehensive review focuses on the hepatic cell type variety, and corresponding applications in 3D models are sparse. Therefore, this review summarizes the characteristics of different cell types and discusses opportunities of different cell types in drug development, liver disease modeling, and liver transplantation.

Angiopoietin-like 4 (ANGPTL4) is a target of hypoxia that accumulates in the endothelial extracellular matrix. While ANGPTL4 is known to regulate angiogenesis and vascular permeability, its context-dependent role related to vascular endothelial growth factor (VEGF) has been suggested in capillary morphogenesis. We here thus develop in vitro 3D models coupled to imaging and morphometric analysis of capillaries to decipher ANGPTL4 functions either alone or in the presence of VEGF. ANGPTL4 induces the formation of barely branched and thin endothelial capillaries that display linear adherens junctions. However, ANGPTL4 counteracts VEGF-induced formation of abundant ramified capillaries presenting cell–cell junctions characterized by VE-cadherin containing reticular plaques and serrated structures. We further deciphered the early angiogenesis steps regulated by ANGPTL4. During the initial activation of endothelial cells, ANGPTL4 alone induces cell shape changes but limits the VEGF-induced cell elongation and unjamming. In the growing sprout, ANGPTL4 maintains cohesive VE-cadherin pattern and sustains moderate 3D cell migration but restricts VEGF-induced endothelium remodeling and cell migration. This effect is mediated by differential short- and long-term regulation of P-Y1175-VEGFR2 and ERK1-2 signaling by ANGPTL4. Our in vitro 3D models thus provide the first evidence that ANGPTL4 induces a specific capillary morphogenesis but also overcomes VEGF effect.

Angiogenesis is the formation of new capillaries from pre-existing blood vessels and participates in proper vasculature development. In pathological conditions such as cancer, abnormal angiogenesis takes place. Angiogenesis is primarily carried out by endothelial cells, the innermost layer of blood vessels. The vascular endothelial growth factor-A (VEGF-A) and its receptor-2 (VEGFR-2) trigger most of the mechanisms activating and regulating angiogenesis, and have been the targets for the development of drugs. However, most experimental assays assessing angiogenesis rely on animal models. We report an in vitro model using a microvessel-on-a-chip. It mimics an effective endothelial sprouting angiogenesis event triggered from an initial microvessel using a single angiogenic factor, VEGF-A. The angiogenic sprouting in this model is depends on the Notch signaling, as observed in vivo. This model enables the study of anti-angiogenic drugs which target a specific factor/receptor pathway, as demonstrated by the use of the clinically approved sorafenib and sunitinib for targeting the VEGF-A/VEGFR-2 pathway. Furthermore, this model allows testing simultaneously angiogenesis and permeability. It demonstrates that sorafenib impairs the endothelial barrier function, while sunitinib does not. Such in vitro human model provides a significant complimentary approach to animal models for the development of effective therapies.

Abstract Elucidating the mechanisms underlying sprouting angiogenesis and permeability should enable the development of more effective therapies for various diseases, including retinopathy, cancer, and other vascular disorders. We focused on epidermal growth factor-like domain 7 (EGFL7) which plays an important role in NOTCH signaling and in the organization of angiogenic sprouts. We developed an EGFL7 -knockdown in vitro microvessel model and investigated the effect of EGFL7 at a tissue level. We found EGFL7 knockdown suppressed VEGF-A-induced sprouting angiogenesis accompanied by an overproduction of endothelial filopodia and reduced collagen IV deposition at the basal side of endothelial cells. We also observed impaired barrier function which reflected an inflammatory condition. Furthermore, our results showed that proper formation of adherens junctions and phosphorylation of VE-cadherin was disturbed. In conclusion, by using a 3D microvessel model we identified novel roles for EGFL7 in endothelial function during sprouting angiogenesis. Highlights • We report new roles of EGFL7 in VEGF-A-stimulated endothelial cells using a human blood vessel-on-a-chip model. • This study reveals EGFL7 interferes with tip/stalk regulation, endothelium integrity, and phosphorylation of VE-cadherin. • The microvessel model demonstrated its capacity to enable elaborate observations for a better understanding of vascular biology. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Decellularized Wharton’s jelly matrix (DWJM) can be used to culture leukemia. • Leukemia cells cultured in DWJM demonstrate increased ALDH expression. • Leukemia cells cultured in DWJM demonstrate increased N -cadherin expression. • Leukemia cells cultured in DWJM demonstrate increased drug resistance. • DWJM could serve as an ECM-based model to study AML stem cell-like behavior. Abstract Acute myeloid leukemia (AML) relapse results from the survival of chemotherapy-resistant and quiescent leukemia stem cells (LSC). These LSCs reside in the bone marrow microenvironment, comprised of other cells and extracellular matrix (ECM), which facilitates LSC quiescence through expression of cell adhesion molecules. We used decellularized Wharton’s jelly matrix (DWJM), the gelatinous material in the umbilical cord, as a scaffolding material to culture leukemia cells, because it contains many components of the bone marrow extracellular matrix, including collagen, fibronectin, lumican, and hyaluronic acid (HA). Leukemia cells cultured in DWJM demonstrated decreased proliferation without undergoing significant differentiation. After culture in DWJM, these cells also exhibited changes in morphology, acquiring a spindle-shaped appearance, and an increase in the ALDH+ cell population. When treated with a high-dose of doxorubicin, leukemia cells in DWJM demonstrated less apoptosis compared with cells in suspension. Serial colony forming unit (CFU) assays indicated that leukemia cells cultured in DWJM showed increased colony-forming ability after both primary and secondary plating. Leukemia cell culture in DWJM was associated with increased N-cadherin expression by flow cytometry. Our data suggest that DWJM could serve as an ECM-based model to study AML stem cell-like cell behavior and chemotherapy sensitivity. [ABSTRACT FROM AUTHOR]

3D culture systems have the ability to mimic the natural microenvironment by allowing better cell-cell interactions. We have prepared an in vitro 3D osteogenic cell culture model using human adipose derived stem cells (hASCs) cultured atop recombinant elastin-like polypeptide (ELP) conjugated to a charged polyelectrolyte, polyethyleneimine (PEI). We demonstrate that hASCs cultured atop the ELP-PEI coated tissue culture polystyrene (TCPS) formed 3D spheroids and exhibited superior differentiation toward osteogenic lineage compared to the traditional two dimensional (2D) monolayer formed atop uncoated TCPS. Live/dead viability assay confirmed >90% live cells at the end of the 3-week culture period. Over the same culture period, higher protein content was observed in 2D monolayer than 3D spheroids, as the 2D environment allowed continued proliferation, while 3D spheroids underwent contact-inhibited growth arrest. The normalized alkaline phosphatase (ALP) activity, which is an indicator for early osteogenic differentiation was higher for 3D spheroids. The normalized osteocalcin (OCN) production, which is an indicator for osteogenic maturation was also higher for 3D spheroids while 2D monolayer had no noticeable OCN production. On day 22, increased Alizarin red uptake by 3D spheroids showed greater mineralization activity than 2D monolayer. Taken together, these results indicate a superior osteogenic differentiation of hASCs in 3D spheroid culture atop ELP-PEI coated TCPS surfaces than the 2D monolayer formed on uncoated TCPS surfaces. Such enhanced osteogenesis in 3D spheroid stem cell culture may serve as an alternative to 2D culture by providing a better microenvironment for the enhanced cellular functions and interactions in bone tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1230-1236, 2017. [ABSTRACT FROM AUTHOR]

In the last few years microfluidics and microfabrication technique principles have been extensively exploited for biomedical applications. In this framework, organs-on-a-chip represent promising tools to reproduce key features of functional tissue units within microscale culture chambers. These systems offer the possibility to investigate the effects of biochemical, mechanical, and electrical stimulations, which are usually applied to enhance the functionality of the engineered tissues. Since the functionality of muscle tissues relies on the 3D organization and on the perfect coupling between electrochemical stimulation and mechanical contraction, great efforts have been devoted to generate biomimetic skeletal and cardiac systems to allow high-throughput pathophysiological studies and drug screening. This review critically analyzes microfluidic platforms that were designed for skeletal and cardiac muscle tissue engineering. Our aim is to highlight which specific features of the engineered systems promoted a typical reorganization of the engineered construct and to discuss how promising design solutions exploited for skeletal muscle models could be applied to improve cardiac tissue models and vice versa. [ABSTRACT FROM AUTHOR]

An in vitro three-dimensional (3D) cell culture system that can mimic organ and tissue structure and function in vivo will be of great benefit for drug discovery and toxicity testing. In this study, the neuroprotective properties of the three most prevalent flavonoid monomers extracted from EGb 761 (isorharmnetin, kaempferol, and quercetin) were investigated using the developed 3D stem cell-derived neural co-culture model. Rat neural stem cells were differentiated into co-culture of both neurons and astrocytes at an equal ratio in the developed 3D model and standard two-dimensional (2D) model using a two-step differentiation protocol for 14 days. The level of neuroprotective effect offered by each flavonoid was found to be aligned with its effect as an antioxidant and its ability to inhibit Caspase-3 activity in a dose-dependent manner. Cell exposure to quercetin (100 µM) following oxidative insult provided the highest levels of neuroprotection in both 2D and 3D models, comparable with exposure to 100 µM of Vitamin E, whilst exposure to isorhamnetin and kaempferol provided a reduced level of neuroprotection in both 2D and 3D models. At lower dosages (10 µM flavonoid concentration), the 3D model was more representative of results previously reported in vivo. The co-cultures of stem cell derived neurons and astrocytes in 3D hydrogel scaffolds as an in vitro neural model closely replicates in vivo results for routine neural drug toxicity and efficacy testing. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:735-744, 2016 [ABSTRACT FROM AUTHOR]

1The interactions between glioma cells and neurons are important for glioma progression but are rarely mimicked and recapitulated in in vitro three-dimensional (3D) models, which may affect the success rate of relevant drug research and development. In this study, an in vitro bioprinted 3D glioma model consisting of an outer hemispherical shell with neurons and an inner hemisphere with glioma cells is proposed to simulate the natural glioma. This model was produced by extrusion-based 3D bioprinting technology. The cells survival rate, morphology, and intercellular Ca 2+ concentration studies were carried out up to 5 days of culturing. It was found that neurons could promote the proliferation of glioma cells around them, associate the morphological changes of glioma cells to be neuron-like, and increase the expression of intracellular Ca 2+ of glioma cells. Conversely, the presence of glioma cells could maintain the neuronal survival rate and promote the neurite outgrowth. The results indicated that glioma cells and neurons facilitated each other implying a symbiotic pattern established between two types of cells during the early stage of glioma development, which were seldom found in the present artificial glioma models. The proposed bioprinted glioma model can mimic the natural microenvironment of glioma tissue, provide an in-depth understanding of cell-cell interactions, and enable pathological and pharmacological studies of glioma., Competing Interests: The authors declare no conflict of interests., (Copyright: © 2023 Bai L, Hao Z, Wang S, et al.)

Bioengineered in vitro three-dimensional (3D) skin model has emerged as a promising tool for recapitulating different types of skin cancer and performing pre-clinical tests. However, a full-thickness 3D model including the epidermis, dermis, and hypodermis layers is scarce despite its significance in human physiology and diverse biological processes. In this book chapter, an attempt has been made to summarize various skin cancer models, including utilized skin layers, materials, cell lines, specific treatments, and fabrication techniques for three types of skin cancer: melanoma, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC). Subsequently, current limitations and future directions of skin cancer models are discussed. The knowledge of the current status of skin cancer models can provide various potential applications in cancer research and thus a more effective way for cancer treatment., (© 2022. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

In the last few years microfluidics and microfabrication technique principles have been extensively exploited for biomedical applications. In this framework, organs-on-a-chip represent promising tools to reproduce key features of functional tissue units within microscale culture chambers. These systems offer the possibility to investigate the effects of biochemical, mechanical, and electrical stimulations, which are usually applied to enhance the functionality of the engineered tissues. Since the functionality of muscle tissues relies on the 3D organization and on the perfect coupling between electrochemical stimulation and mechanical contraction, great efforts have been devoted to generate biomimetic skeletal and cardiac systems to allow high-throughput pathophysiological studies and drug screening. This review critically analyzes microfluidic platforms that were designed for skeletal and cardiac muscle tissue engineering. Our aim is to highlight which specific features of the engineered systems promoted a typical reorganization of the engineered construct and to discuss how promising design solutions exploited for skeletal muscle models could be applied to improve cardiac tissue models and vice versa.

Angiopoietin-like 4 (ANGPTL4) is a target of hypoxia that accumulates in the endothelial extracellular matrix. While ANGPTL4 is known to regulate angiogenesis and vascular permeability, its context-dependent role related to vascular endothelial growth factor (VEGF) has been suggested in capillary morphogenesis. We here thus develop in vitro 3D models coupled to imaging and morphometric analysis of capillaries to decipher ANGPTL4 functions either alone or in the presence of VEGF. ANGPTL4 induces the formation of barely branched and thin endothelial capillaries that display linear adherens junctions. However, ANGPTL4 counteracts VEGF-induced formation of abundant ramified capillaries presenting cell–cell junctions characterized by VE-cadherin containing reticular plaques and serrated structures. We further deciphered the early angiogenesis steps regulated by ANGPTL4. During the initial activation of endothelial cells, ANGPTL4 alone induces cell shape changes but limits the VEGF-induced cell elongation and unjamming. In the growing sprout, ANGPTL4 maintains cohesive VE-cadherin pattern and sustains moderate 3D cell migration but restricts VEGF-induced endothelium remodeling and cell migration. This effect is mediated by differential short- and long-term regulation of P-Y1175-VEGFR2 and ERK1-2 signaling by ANGPTL4. Our in vitro 3D models thus provide the first evidence that ANGPTL4 induces a specific capillary morphogenesis but also overcomes VEGF effect. [ABSTRACT FROM AUTHOR]

Liquid plug therapies are commonly instilled in premature babies suffering from infant respiratory distress syndrome (IRDS) by a procedure called surfactant replacement therapy (SRT) in which a surfactant-laden bolus is instilled endotracheally in the neonatal lungs, dramatically reducing mortality and morbidity in neonatal populations. Since data are frequently limited, the optimal method for surfactant delivery has yet to be established towards more standardized guidelines. Here, we explore the dynamics of liquid plug transport using an anatomically-relevant, true-scale in vitro 3D model of the upper airways of a premature infant. We quantify the initial plug's distribution as a function of two underlying parameters that can be clinically controlled; namely, the injection flow rate and the viscosity of the administered fluid. By extracting a homogeneity index (HI), our in vitro results underline how the combination of both high fluid viscosity and injection flow rates may be advantageous in improving homogeneous dispersion. Such outcomes are anticipated to help refine future SRT administration guidelines towards more uniform distribution using more anatomically-realistic 3D in vitro models at true scale of the preterm neonate. [ABSTRACT FROM AUTHOR]

Owing to retained hepatic phenotypes and functions, human three-dimensional (3D) hepatic models established with diverse hepatic cell types are thought to recoup the gaps in drug development and disease modeling limited by a conventional two-dimensional (2D) cell culture system and species-specific variability in drug metabolizing enzymes and transporters. Primary human hepatocytes, human hepatic cancer cell lines, and human stem cell-derived hepatocyte-like cells are three main hepatic cell types used in current models and exhibit divergent hepatic phenotypes. Primary human hepatocytes derived from healthy hepatic parenchyma resemble in vivo -like genetic and metabolic profiling. Human hepatic cancer cell lines are unlimitedly reproducible and tumorigenic. Stem cell-derived hepatocyte-like cells derived from patients are promising to retain the donor's genetic background. It has been suggested in some studies that unique properties of cell types endue them with benefits in different research fields of in vitro 3D modeling paradigm. For instance, the primary human hepatocyte was thought to be the gold standard for hepatotoxicity study, and stem cell-derived hepatocyte-like cells have taken a main role in personalized medicine and regenerative medicine. However, the comprehensive review focuses on the hepatic cell type variety, and corresponding applications in 3D models are sparse. Therefore, this review summarizes the characteristics of different cell types and discusses opportunities of different cell types in drug development, liver disease modeling, and liver transplantation., Competing Interests: The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Xu.)

The role of astrocytes in the glioblastoma (GBM) microenvironment is poorly understood; particularly with regard to cell invasion and drug resistance. To assess this role of astrocytes in GBMs we established an all human 2D co-culture model and a 3D hyaluronic acid-gelatin based hydrogel model (HyStem™-HP) with different ratios of GBM cells to astrocytes. A contact co-culture of fluorescently labelled GBM cells and astrocytes showed that the latter promotes tumour growth and migration of GBM cells. Notably, the presence of non-neoplastic astrocytes in direct contact, even in low amounts in co-culture, elicited drug resistance in GBM. Recent studies showed that non-neoplastic cells can transfer mitochondria along tunneling nanotubes (TNT) and rescue damaged target cancer cells. In these studies, we explored TNT formation and mitochondrial transfer using 2D and 3D in vitro co-culture models of GBM and astrocytes. TNT formation occurs in glial fibrillary acidic protein (GFAP) positive "reactive" astrocytes after 48 h co-culture and the increase of TNT formations was greater in 3D hyaluronic acid-gelatin based hydrogel models. This study shows that human astrocytes in the tumour microenvironment, both in 2D and 3D in vitro co-culture models, could form TNT connections with GBM cells. We postulate that the association on TNT delivery non-neoplastic mitochondria via a TNT connection may be related to GBM drug response as well as proliferation and migration. [ABSTRACT FROM AUTHOR]

Triggering receptor expressed on myeloid cells-2 (TREM-2), a transmembrane receptor expressed by macrophages, microglia, and osteoclasts (OCs), plays a protective role in late-onset Alzheimer Disease (AD). To validate TREM-2 as a therapeutic target in AD, its potential secondary parallel effect on bone homeostasis should be clarified. However, animal models and monolayer cultures of human cells were shown poorly predictive of TREM-2 function in human. Therefore, this study aimed to engineer a tridimensional in vitro model using human progenitors differentiated into osteoblasts and OCs, recapitulating physiological bone homeostasis. Human bone marrow-derived mesenchymal cells were seeded and cultured under perfusion inside a collagen type I scaffold for 3 weeks, generating osteoblasts and mineralized matrix. Human peripheral blood-derived CD14 + monocytes were subsequently seeded through the generated tissue, thanks to perfusion flow, and further cultured for up to 3 weeks with an inductive medium, generating mature OCs. This culture system supported collagenous matrix deposition and resorption, allowing for the investigation of kinetic of soluble TREM-2 over the coculture time. Agonistic activation of TREM-2 in this model had no effect on OC activity or on mineralized matrix turnover. In conclusion, the engineered culture system represents a tridimensional, in vitro human bone model for drug testing and suggested no effect of TREM-2 agonist on bone resorption.

Angiogenesis is the formation of new capillaries from pre-existing blood vessels and participates in proper vasculature development. In pathological conditions such as cancer, abnormal angiogenesis takes place. Angiogenesis is primarily carried out by endothelial cells, the innermost layer of blood vessels. The vascular endothelial growth factor-A (VEGF-A) and its receptor-2 (VEGFR-2) trigger most of the mechanisms activating and regulating angiogenesis, and have been the targets for the development of drugs. However, most experimental assays assessing angiogenesis rely on animal models. We report an in vitro model using a microvessel-on-a-chip. It mimics an effective endothelial sprouting angiogenesis event triggered from an initial microvessel using a single angiogenic factor, VEGF-A. The angiogenic sprouting in this model is depends on the Notch signaling, as observed in vivo. This model enables the study of anti-angiogenic drugs which target a specific factor/receptor pathway, as demonstrated by the use of the clinically approved sorafenib and sunitinib for targeting the VEGF-A/VEGFR-2 pathway. Furthermore, this model allows testing simultaneously angiogenesis and permeability. It demonstrates that sorafenib impairs the endothelial barrier function, while sunitinib does not. Such in vitro human model provides a significant complimentary approach to animal models for the development of effective therapies., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

The vascular barrier is an important function of the endothelium and its dysfunction is involved in several diseases. The barrier function of the endothelial cell monolayer is governed by cell-cell, cell-extracellular matrix (cell-ECM) contacts, and inflammatory factors such as thrombin, histamine or vascular endothelial growth factor. Several in vivo and in vitro assays that measure the vascular permeability induced by these factors have been developed. However, they suffer limitations such as being challenging for assessing details of biological processes at a cellular level or lacking the architecture of a vessel, that raise the need for new methods. In vitro 3D model-based assays have thus been developed but assays for investigating compounds that protects the barrier function are lacking. Here we describe the development of an in vitro three-dimensional (3D) vascular endothelium model in which we can manipulate the endothelial barrier function and permeability to molecules, which have a molecular weight similar to human serum albumin, allowing to assess the protective effect of compounds. A microvessel was prepared by culturing human umbilical vein endothelial cells (HUVECs) within a collagen gel on a polydimethylsiloxane (PDMS) chip. Using fluorescein isothiocyanate (FITC)-conjugated dextran (70 kDa, FITC-dextran) and confocal fluorescence microscopy, we showed that the microvessel presented an effective barrier function. We were then able to induce the loss of this barrier function by treatment with the inflammatory factor thrombin. The loss of barrier function was quantified by the extravasation of FITC-dextran into collagen matrix. Furthermore, we were able to analyze the protective effect on the endothelial barrier function of the cyclic adenosine monophosphate (cAMP) analog, 8-pCPT-2'-O-Me-cAMP (also called 007). In an attempt to understand the effects of thrombin and 007 in our model, we analyzed the adherens junctions and cytoskeleton through immunostaining of the vascular endothelial cadherin and actin, respectively. Our assay method could be used to screen for compounds modulating the barrier function of endothelial cells, as well as investigating mechanistic aspects of barrier dysfunction., Competing Interests: Competing Interests: The authors have declared that no competing interest exists.

An in vitro three-dimensional (3D) cell culture system that can mimic organ and tissue structure and function in vivo will be of great benefit for drug discovery and toxicity testing. In this study, the neuroprotective properties of the three most prevalent flavonoid monomers extracted from EGb 761 (isorharmnetin, kaempferol, and quercetin) were investigated using the developed 3D stem cell-derived neural co-culture model. Rat neural stem cells were differentiated into co-culture of both neurons and astrocytes at an equal ratio in the developed 3D model and standard two-dimensional (2D) model using a two-step differentiation protocol for 14 days. The level of neuroprotective effect offered by each flavonoid was found to be aligned with its effect as an antioxidant and its ability to inhibit Caspase-3 activity in a dose-dependent manner. Cell exposure to quercetin (100 µM) following oxidative insult provided the highest levels of neuroprotection in both 2D and 3D models, comparable with exposure to 100 µM of Vitamin E, whilst exposure to isorhamnetin and kaempferol provided a reduced level of neuroprotection in both 2D and 3D models. At lower dosages (10 µM flavonoid concentration), the 3D model was more representative of results previously reported in vivo. The co-cultures of stem cell derived neurons and astrocytes in 3D hydrogel scaffolds as an in vitro neural model closely replicates in vivo results for routine neural drug toxicity and efficacy testing. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:735-744, 2016., (© 2016 American Institute of Chemical Engineers.)