@article{mote_kubik_polacheck_baker_trappmann_2024, title={A nanoporous hydrogel-based model to study chemokine gradient-driven angiogenesis under luminal flow}, ISSN={["1473-0189"]}, DOI={10.1039/d4lc00460d}, abstractNote={The growth of new blood vessels through angiogenesis is a highly coordinated process, which is initiated by chemokine gradients that activate endothelial cells within a perfused parent vessel to sprout into the surrounding 3D tissue matrix. While both biochemical signals from pro-angiogenic factors, as well as mechanical cues originating from luminal fluid flow that exerts shear stress on the vessel wall, have individually been identified as major regulators of endothelial cell sprouting, it remains unclear whether and how both types of cues synergize. To fill this knowledge gap, here, we created a 3D biomimetic model of chemokine gradient-driven angiogenic sprouting, in which a micromolded tube inside a hydrogel matrix is seeded with endothelial cells and connected to a perfusion system to control fluid flow rates and resulting shear forces on the vessel wall. To allow for the formation of chemokine gradients despite the presence of luminal flow, a nanoporous synthetic hydrogel that supports angiogenesis but limits the interstitial flow proved crucial. Using this system, we find that luminal flow and resulting shear stress is a major regulator of the speed and morphogenesis of angiogenic sprouting, whose action is mediated through changes in vascular permeability.}, journal={LAB ON A CHIP}, author={Mote, Nidhi and Kubik, Sarah and Polacheck, William J. and Baker, Brendon M. and Trappmann, Britta}, year={2024}, month={Sep} } @article{farber_dong_wang_rathod_wang_dixit_keepers_xie_butz_polacheck_et al._2024, title={Direct conversion of cardiac fibroblasts into endothelial-like cells using Sox17 and Erg}, volume={15}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-024-48354-6}, abstractNote={Abstract Endothelial cells are a heterogeneous population with various organ-specific and conserved functions that are critical to organ development, function, and regeneration. Here we report a Sox17 - Erg direct reprogramming approach that uses cardiac fibroblasts to create differentiated endothelial cells that demonstrate endothelial-like molecular and physiological functions in vitro and in vivo. Injection of these induced endothelial cells into myocardial infarct sites after injury results in improved vascular perfusion of the scar region. Furthermore, we use genomic analyses to illustrate that Sox17 - Erg reprogramming instructs cardiac fibroblasts toward an arterial-like identity. This results in a more efficient direct conversion of fibroblasts into endothelial-like cells when compared to traditional Etv2 -based reprogramming. Overall, this Sox17 - Erg direct reprogramming strategy offers a robust tool to generate endothelial cells both in vitro and in vivo, and has the potential to be used in repairing injured tissue.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Farber, Gregory and Dong, Yanhan and Wang, Qiaozi and Rathod, Mitesh and Wang, Haofei and Dixit, Michelle and Keepers, Benjamin and Xie, Yifang and Butz, Kendall and Polacheck, William J. and et al.}, year={2024}, month={May} } @article{rathod_aw_huang_lu_doherty_whithworth_xi_roy-chaudhury_polacheck_2024, title={Donor-Derived Engineered Microvessels for Cardiovascular Risk Stratification of Patients with Kidney Failure}, ISSN={["1613-6829"]}, DOI={10.1002/smll.202307901}, abstractNote={AbstractCardiovascular disease is the cause of death in ≈50% of hemodialysis patients. Accumulation of uremic solutes in systemic circulation is thought to be a key driver of the endothelial dysfunction that underlies elevated cardiovascular events. A challenge in understanding the mechanisms relating chronic kidney disease to cardiovascular disease is the lack of in vitro models that allow screening of the effects of the uremic environment on the endothelium. Here, a method is described for microfabrication of human blood vessels from donor cells and perfused with donor serum. The resulting donor‐derived microvessels are used to quantify vascular permeability, a hallmark of endothelial dysfunction, in response to serum spiked with pathophysiological levels of indoxyl sulfate, and in response to serum from patients with chronic kidney disease and from uremic pigs. The uremic environment has pronounced effects on microvascular integrity as demonstrated by irregular cell–cell junctions and increased permeability in comparison to cell culture media and healthy serum. Moreover, the engineered microvessels demonstrate an increase in sensitivity compared to traditional 2D assays. Thus, the devices and the methods presented here have the potential to be utilized to risk stratify and to direct personalized treatments for patients with chronic kidney disease.}, journal={SMALL}, author={Rathod, Mitesh L. and Aw, Wen Yih and Huang, Stephanie and Lu, Jingming and Doherty, Elizabeth L. and Whithworth, Chloe P. and Xi, Gang and Roy-Chaudhury, Prabir and Polacheck, William J.}, year={2024}, month={Jan} } @article{whitworth_aw_doherty_handler_ambekar_sawhney_scarcelli_polacheck_2024, title={P300 Modulates Endothelial Mechanotransduction of Fluid Shear Stress}, ISSN={["1865-5033"]}, DOI={10.1007/s12195-024-00805-2}, journal={CELLULAR AND MOLECULAR BIOENGINEERING}, author={Whitworth, Chloe P. and Aw, Wen Y. and Doherty, Elizabeth L. and Handler, Chenchen and Ambekar, Yogeshwari and Sawhney, Aanya and Scarcelli, Giuliano and Polacheck, William J.}, year={2024}, month={Jun} } @article{aw_cho_wang_cooper_doherty_rocco_huang_kubik_whitworth_armstrong_et al._2023, title={Microphysiological model of PIK3CA-driven vascular malformations reveals a role of dysregulated Rac1 and mTORC1/2 in lesion formation}, volume={9}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.ade8939}, abstractNote={ Somatic activating mutations of PIK3CA are associated with development of vascular malformations (VMs). Here, we describe a microfluidic model of PIK3CA -driven VMs consisting of human umbilical vein endothelial cells expressing PIK3CA activating mutations embedded in three-dimensional hydrogels. We observed enlarged, irregular vessel phenotypes and the formation of cyst-like structures consistent with clinical signatures and not previously observed in cell culture models. Pathologic morphologies occurred concomitant with up-regulation of Rac1/p21-activated kinase (PAK), mitogen-activated protein kinase cascades (MEK/ERK), and mammalian target of rapamycin (mTORC1/2) signaling networks. We observed differential effects between alpelisib, a PIK3CA inhibitor, and rapamycin, an mTORC1 inhibitor, in mitigating matrix degradation and network topology. While both were effective in preventing vessel enlargement, rapamycin failed to reduce MEK/ERK and mTORC2 activity and resulted in hyperbranching, while inhibiting PAK, MEK1/2, and mTORC1/2 mitigates abnormal growth and vascular dilation. Collectively, these findings demonstrate an in vitro platform for VMs and establish a role of dysregulated Rac1/PAK and mTORC1/2 signaling in PIK3CA -driven VMs. }, number={7}, journal={SCIENCE ADVANCES}, author={Aw, Wen Yih and Cho, Crescentia and Wang, Hao and Cooper, Anne Hope and Doherty, Elizabeth L. and Rocco, David and Huang, Stephanie A. and Kubik, Sarah and Whitworth, Chloe P. and Armstrong, Ryan and et al.}, year={2023}, month={Feb} } @article{doherty_aw_warren_hockenberry_whitworth_krohn_howell_diekman_legant_nia_et al._2023, title={Patient-derived extracellular matrix demonstrates role of COL3A1 in blood vessel mechanics}, volume={166}, ISSN={["1878-7568"]}, DOI={10.1016/j.actbio.2023.05.015}, abstractNote={Vascular Ehlers-Danlos Syndrome (vEDS) is a rare autosomal dominant disease caused by mutations in the COL3A1 gene, which renders patients susceptible to aneurysm and arterial dissection and rupture. To determine the role of COL3A1 variants in the biochemical and biophysical properties of human arterial ECM, we developed a method for synthesizing ECM directly from vEDS donor fibroblasts. We found that the protein content of the ECM generated from vEDS donor fibroblasts differed significantly from ECM from healthy donors, including upregulation of collagen subtypes and other proteins related to ECM structural integrity. We further found that ECM generated from a donor with a glycine substitution mutation was characterized by increased glycosaminoglycan content and unique viscoelastic mechanical properties, including increased time constant for stress relaxation, resulting in a decrease in migratory speed of human aortic endothelial cells when seeded on the ECM. Collectively, these results demonstrate that vEDS patient-derived fibroblasts harboring COL3A1 mutations synthesize ECM that differs in composition, structure, and mechanical properties from healthy donors. These results further suggest that ECM mechanical properties could serve as a prognostic indicator for patients with vEDS, and the insights provided by the approach demonstrate the broader utility of cell-derived ECM in disease modeling. The role of collagen III ECM mechanics remains unclear, despite reported roles in diseases including fibrosis and cancer. Here, we generate fibrous, collagen-rich ECM from primary donor cells from patients with vascular Ehlers-Danlos syndrome (vEDS), a disease caused by mutations in the gene that encodes collagen III. We observe that ECM grown from vEDS patients is characterized by unique mechanical signatures, including altered viscoelastic properties. By quantifying the structural, biochemical, and mechanical properties of patient-derived ECM, we identify potential drug targets for vEDS, while defining a role for collagen III in ECM mechanics more broadly. Furthermore, the structure/function relationships of collagen III in ECM assembly and mechanics will inform the design of substrates for tissue engineering and regenerative medicine.}, journal={ACTA BIOMATERIALIA}, author={Doherty, Elizabeth L. and Aw, Wen Yih and Warren, Emily C. and Hockenberry, Max and Whitworth, Chloe P. and Krohn, Grace and Howell, Stefanie and Diekman, Brian O. and Legant, Wesley R. and Nia, Hadi Tavakoli and et al.}, year={2023}, month={Aug}, pages={346–359} } @article{whitworth_polacheck_2023, title={Vascular organs-on-chip made with patient-derived endothelial cells: technologies to transform drug discovery and disease modeling}, ISSN={["1746-045X"]}, DOI={10.1080/17460441.2023.2294947}, abstractNote={INTRODUCTION Vascular diseases impart a tremendous burden on healthcare systems in the United States and across the world. Efforts to improve therapeutic interventions are hindered by limitations of current experimental models. The integration of patient-derived cells with organ-on-chip (OoC) technology is a promising avenue for preclinical drug screening that improves upon traditional cell culture and animal models. AREAS COVERED The authors review induced pluripotent stem cells (iPSC) and blood outgrowth endothelial cells (BOEC) as two sources for patient-derived endothelial cells (EC). They summarize several studies that leverage patient-derived EC and OoC for precision disease modeling of the vasculature, with a focus on applications for drug discovery. They also highlight the utility of patient-derived EC in other translational endeavors, including ex vivo organogenesis and multi-organ-chip integration. EXPERT OPINION Precision disease modeling continues to mature in the academic space, but end-use by pharmaceutical companies is currently limited. To fully realize their transformative potential, OoC systems must balance their complexity with their ability to integrate with the highly standardized and high-throughput experimentation required for drug discovery and development.}, journal={EXPERT OPINION ON DRUG DISCOVERY}, author={Whitworth, Chloe P. and Polacheck, William J.}, year={2023}, month={Dec} } @article{chhabra_song_grzelak_polacheck_fleming_chen_bhatia_2022, title={A vascularized model of the human liver mimics regenerative responses}, volume={119}, ISSN={["1091-6490"]}, DOI={10.1073/pnas.2115867119}, abstractNote={Liver regeneration is a well-orchestrated process that is typically studied in animal models. Although previous animal studies have offered many insights into liver regeneration, human biology is less well understood. To this end, we developed a three-dimensional (3D) platform called structurally vascularized hepatic ensembles for analyzing regeneration (SHEAR) to model multiple aspects of human liver regeneration. SHEAR enables control over hemodynamic alterations to mimic those that occur during liver injury and regeneration and supports the administration of biochemical inputs such as cytokines and paracrine interactions with endothelial cells. We found that exposing the endothelium-lined channel to fluid flow led to increased secretion of regeneration-associated factors. Stimulation with relevant cytokines not only amplified the secretory response, but also induced cell-cycle entry of primary human hepatocytes (PHHs) embedded within the device. Further, we identified endothelial-derived mediators that are sufficient to initiate proliferation of PHHs in this context. Collectively, the data presented here underscore the importance of multicellular models that can recapitulate high-level tissue functions and demonstrate that the SHEAR device can be used to discover and validate conditions that promote human liver regeneration.}, number={28}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Chhabra, Arnav and Song, H-H Greco and Grzelak, Katarzyna A. and Polacheck, William J. and Fleming, Heather E. and Chen, Christopher S. and Bhatia, Sangeeta N.}, year={2022}, month={Jul} } @article{lee_huang_aw_rathod_cho_ligler_polacheck_2022, title={Multilayer microfluidic platform for the study of luminal, transmural, and interstitial flow}, volume={14}, ISSN={["1758-5090"]}, DOI={10.1088/1758-5090/ac48e5}, abstractNote={Abstract Efficient delivery of oxygen and nutrients to tissues requires an intricate balance of blood, lymphatic, and interstitial fluid pressures (IFPs), and gradients in fluid pressure drive the flow of blood, lymph, and interstitial fluid through tissues. While specific fluid mechanical stimuli, such as wall shear stress, have been shown to modulate cellular signaling pathways along with gene and protein expression patterns, an understanding of the key signals imparted by flowing fluid and how these signals are integrated across multiple cells and cell types in native tissues is incomplete due to limitations with current assays. Here, we introduce a multi-layer microfluidic platform (MμLTI-Flow) that enables the culture of engineered blood and lymphatic microvessels and independent control of blood, lymphatic, and IFPs. Using optical microscopy methods to measure fluid velocity for applied input pressures, we demonstrate varying rates of interstitial fluid flow as a function of blood, lymphatic, and interstitial pressure, consistent with computational fluid dynamics (CFD) models. The resulting microfluidic and computational platforms will provide for analysis of key fluid mechanical parameters and cellular mechanisms that contribute to diseases in which fluid imbalances play a role in progression, including lymphedema and solid cancer.}, number={2}, journal={BIOFABRICATION}, author={Lee, Gi-hun and Huang, Stephanie A. and Aw, Wen Y. and Rathod, Mitesh L. and Cho, Crescentia and Ligler, Frances S. and Polacheck, William J.}, year={2022}, month={Apr} } @article{wang_kent_huang_jarman_shikanov_davidson_hiraki_lin_wall_matera_et al._2021, title={Direct comparison of angiogenesis in natural and synthetic biomaterials reveals that matrix porosity regulates endothelial cell invasion speed and sprout diameter}, volume={135}, ISSN={["1878-7568"]}, DOI={10.1016/j.actbio.2021.08.038}, abstractNote={Vascularization of large, diffusion-hindered biomaterial implants requires an understanding of how extracellular matrix (ECM) properties regulate angiogenesis. Sundry biomaterials assessed across many disparate angiogenesis assays have highlighted ECM determinants that influence this complex multicellular process. However, the abundance of material platforms, each with unique parameters to model endothelial cell (EC) sprouting presents additional challenges of interpretation and comparison between studies. In this work we directly compared the angiogenic potential of commonly utilized natural (collagen and fibrin) and synthetic dextran vinyl sulfone (DexVS) hydrogels in a multiplexed angiogenesis-on-a-chip platform. Modulating matrix density of collagen and fibrin hydrogels confirmed prior findings that increases in matrix density correspond to increased EC invasion as connected, multicellular sprouts, but with decreased invasion speeds. Angiogenesis in synthetic DexVS hydrogels, however, resulted in fewer multicellular sprouts. Characterizing hydrogel Young's modulus and permeability (a measure of matrix porosity), we identified matrix permeability to significantly correlate with EC invasion depth and sprout diameter. Although microporous collagen and fibrin hydrogels produced lumenized sprouts in vitro, they rapidly resorbed post-implantation into the murine epididymal fat pad. In contrast, DexVS hydrogels proved comparatively stable. To enhance angiogenesis within DexVS hydrogels, we incorporated sacrificial microgels to generate cell-scale pores throughout the hydrogel. Microporous DexVS hydrogels resulted in lumenized sprouts in vitro and enhanced cell invasion in vivo. Towards the design of vascularized biomaterials for long-term regenerative therapies, this work suggests that synthetic biomaterials offer improved size and shape control following implantation and that tuning matrix porosity may better support host angiogenesis. Understanding how extracellular matrix properties govern angiogenesis will inform biomaterial design for engineering vascularized implantable grafts. Here, we utilized a multiplexed angiogenesis-on-a-chip platform to compare the angiogenic potential of natural (collagen and fibrin) and synthetic dextran vinyl sulfone (DexVS) hydrogels. Characterization of matrix properties and sprout morphometrics across these materials points to matrix porosity as a critical regulator of sprout invasion speed and diameter, supported by the observation that nanoporous DexVS hydrogels yielded endothelial cell sprouts that were not perfusable. To enhance angiogenesis into synthetic hydrogels, we incorporated sacrificial microgels to generate microporosity. We find that microporosity increased sprout diameter in vitro and cell invasion in vivo. This work establishes a composite materials approach to enhance the vascularization of synthetic hydrogels.}, journal={ACTA BIOMATERIALIA}, author={Wang, William Y. and Kent, Robert N., III and Huang, Stephanie A. and Jarman, Evan H. and Shikanov, Eve H. and Davidson, Christopher D. and Hiraki, Harrison L. and Lin, Daphne and Wall, Monica A. and Matera, Daniel L. and et al.}, year={2021}, month={Nov}, pages={260–273} } @misc{rickard_conrad_sorrin_ruhi_reader_huang_franco_scarcelli_polacheck_roque_et al._2021, title={Malignant Ascites in Ovarian Cancer: Cellular, Acellular, and Biophysical Determinants of Molecular Characteristics and Therapy Response}, volume={13}, ISSN={["2072-6694"]}, url={https://www.mdpi.com/2072-6694/13/17/4318}, DOI={10.3390/cancers13174318}, abstractNote={Ascites refers to the abnormal accumulation of fluid in the peritoneum resulting from an underlying pathology, such as metastatic cancer. Among all cancers, advanced-stage epithelial ovarian cancer is most frequently associated with the production of malignant ascites and is the leading cause of death from gynecologic malignancies. Despite decades of evidence showing that the accumulation of peritoneal fluid portends the poorest outcomes for cancer patients, the role of malignant ascites in promoting metastasis and therapy resistance remains poorly understood. This review summarizes the current understanding of malignant ascites, with a focus on ovarian cancer. The first section provides an overview of heterogeneity in ovarian cancer and the pathophysiology of malignant ascites. Next, analytical methods used to characterize the cellular and acellular components of malignant ascites, as well the role of these components in modulating cell biology, are discussed. The review then provides a perspective on the pressures and forces that tumors are subjected to in the presence of malignant ascites and the impact of physical stress on therapy resistance. Treatment options for malignant ascites, including surgical, pharmacological and photochemical interventions are then discussed to highlight challenges and opportunities at the interface of drug discovery, device development and physical sciences in oncology.}, number={17}, journal={CANCERS}, publisher={MDPI AG}, author={Rickard, Brittany P. and Conrad, Christina and Sorrin, Aaron J. and Ruhi, Mustafa Kemal and Reader, Jocelyn C. and Huang, Stephanie A. and Franco, Walfre and Scarcelli, Giuliano and Polacheck, William J. and Roque, Dana M. and et al.}, year={2021}, month={Sep} } @article{perez-rodriguez_huang_borau_manuel garcia-aznar_polacheck_2021, title={Microfluidic model of monocyte extravasation reveals the role of hemodynamics and subendothelial matrix mechanics in regulating endothelial integrity}, volume={15}, ISSN={["1932-1058"]}, DOI={10.1063/5.0061997}, abstractNote={Extravasation of circulating cells is an essential process that governs tissue inflammation and the body's response to pathogenic infection. To initiate anti-inflammatory and phagocytic functions within tissues, immune cells must cross the vascular endothelial barrier from the vessel lumen to the subluminal extracellular matrix. In this work, we present a microfluidic approach that enables the recreation of a three-dimensional, perfused endothelial vessel formed by human endothelial cells embedded within a collagen-rich matrix. Monocytes are introduced into the vessel perfusate, and we investigate the role of luminal flow and collagen concentration on extravasation. In vessels conditioned with the flow, increased monocyte adhesion to the vascular wall was observed, though fewer monocytes extravasated to the collagen hydrogel. Our results suggest that the lower rates of extravasation are due to the increased vessel integrity and reduced permeability of the endothelial monolayer. We further demonstrate that vascular permeability is a function of collagen hydrogel mass concentration, with increased collagen concentrations leading to elevated vascular permeability and increased extravasation. Collectively, our results demonstrate that extravasation of monocytes is highly regulated by the structural integrity of the endothelial monolayer. The microfluidic approach developed here allows for the dissection of the relative contributions of these cues to further understand the key governing processes that regulate circulating cell extravasation and inflammation.}, number={5}, journal={BIOMICROFLUIDICS}, author={Perez-Rodriguez, Sandra and Huang, Stephanie A. and Borau, Carlos and Manuel Garcia-Aznar, Jose and Polacheck, William J.}, year={2021}, month={Sep} } @article{wang_lin_jarman_polacheck_baker_2020, title={Functional angiogenesis requires microenvironmental cues balancing endothelial cell migration and proliferation}, volume={20}, ISSN={["1473-0189"]}, DOI={10.1039/c9lc01170f}, abstractNote={The formation of functional microvasculature results from physical and soluble microenvironmental cues that balance endothelial cell migration with proliferation during multicellular sprouting morphogenesis.}, number={6}, journal={LAB ON A CHIP}, author={Wang, William Y. and Lin, Daphne and Jarman, Evan H. and Polacheck, William J. and Baker, Brendon M.}, year={2020}, month={Mar}, pages={1153–1166} } @article{griffith_huang_cho_khare_rich_lee_ligler_diekman_polacheck_2020, title={Microfluidics for the study of mechanotransduction}, volume={53}, ISSN={["1361-6463"]}, DOI={10.1088/1361-6463/ab78d4}, abstractNote={Mechanical forces regulate a diverse set of biological processes at cellular, tissue, and organismal length scales. Investigating the cellular and molecular mechanisms that underlie the conversion of mechanical forces to biological responses is challenged by limitations of traditional animal models and in vitro cell culture, including poor control over applied force and highly artificial cell culture environments. Recent advances in fabrication methods and material processing have enabled the development of microfluidic platforms that provide precise control over the mechanical microenvironment of cultured cells. These devices and systems have proven to be powerful for uncovering and defining mechanisms of mechanotransduction. In this review, we first give an overview of the main mechanotransduction pathways that function at sites of cell adhesion, many of which have been investigated with microfluidics. We then discuss how distinct microfluidic fabrication methods can be harnessed to gain biological insight, with description of both monolithic and replica molding approaches. Finally, we present examples of how microfluidics can be used to apply both solid forces (substrate mechanics, strain, and compression) and fluid forces (luminal, interstitial) to cells. Throughout the review, we emphasize the advantages and disadvantages of different fabrication methods and applications of force in order to provide perspective to investigators looking to apply forces to cells in their own research.}, number={22}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Griffith, Christian M. and Huang, Stephanie A. and Cho, Crescentia and Khare, Tanmay M. and Rich, Matthew and Lee, Gi-hun and Ligler, Frances S. and Diekman, Brian O. and Polacheck, William J.}, year={2020}, month={May} } @article{du_khandekar_llewellyn_polacheck_chen_wells_2020, title={A Bile Duct-on-a-Chip With Organ-Level Functions}, volume={71}, ISSN={["1527-3350"]}, DOI={10.1002/hep.30918}, abstractNote={ Background and Aims Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are frequently associated with damage to the barrier function of the biliary epithelium. Here, we report on a bile duct‐on‐a‐chip that phenocopies not only the tubular architecture of the bile duct in three dimensions, but also its barrier functions. Approach and Results We showed that mouse cholangiocytes in the channel of the device became polarized and formed mature tight junctions, that the permeability of the cholangiocyte monolayer was comparable to ex vivo measurements, and that cholangiocytes in the device were mechanosensitive (as demonstrated by changes in calcium flux under applied luminal flow). Permeability decreased significantly when cells formed a compact monolayer with cell densities comparable to those observed in vivo. This device enabled independent access to the apical and basolateral surfaces of the cholangiocyte channel, allowing proof‐of‐concept toxicity studies with the biliary toxin, biliatresone, and the bile acid, glycochenodeoxycholic acid. The cholangiocyte basolateral side was more vulnerable than the apical side to treatment with either agent, suggesting a protective adaptation of the apical surface that is normally exposed to bile. Further studies revealed a protective role of the cholangiocyte apical glycocalyx, wherein disruption of the glycocalyx with neuraminidase increased the permeability of the cholangiocyte monolayer after treatment with glycochenodeoxycholic acid. Conclusions This bile duct‐on‐a‐chip captured essential features of a simplified bile duct in structure and organ‐level functions and represents an in vitro platform to study the pathophysiology of the bile duct using cholangiocytes from a variety of sources. }, number={4}, journal={HEPATOLOGY}, author={Du, Yu and Khandekar, Gauri and Llewellyn, Jessica and Polacheck, William and Chen, Christopher S. and Wells, Rebecca G.}, year={2020}, month={Apr}, pages={1350–1363} } @article{polacheck_kutys_tefft_chen_2019, title={Microfabricated blood vessels for modeling the vascular transport barrier}, volume={14}, ISSN={["1750-2799"]}, DOI={10.1038/s41596-019-0144-8}, abstractNote={The vascular endothelium forms the inner lining of blood vessels and actively regulates vascular permeability in response to chemical and physical stimuli. Understanding the molecular pathways and mechanisms that regulate the permeability of blood vessels is of critical importance for developing therapies for cardiovascular dysfunction and disease. Recently, we developed a novel microfluidic human engineered microvessel (hEMV) platform to enable controlled blood flow through a human endothelial lumen within a physiologic 3D extracellular matrix (ECM) into which pericytes and other stromal cells can be introduced to recapitulate tissue-specific microvascular physiology. This protocol describes how to design and fabricate the silicon hEMV device master molds (takes ~1 week) and elastomeric substrates (takes 3 d); how to seed, culture, and apply calibrated fluid shear stress to hEMVs (takes 1–7 d); and how to assess vascular barrier function (takes 1 d) and perform immunofluorescence imaging (takes 3 d). Cells are seeded into an extracellular matrix template and flow is applied to create microfabricated blood vessels.}, number={5}, journal={NATURE PROTOCOLS}, author={Polacheck, William J. and Kutys, Matthew L. and Tefft, Juliann B. and Chen, Christopher S.}, year={2019}, month={May}, pages={1425–1454} }