William J Polacheck

• PhD
• Professor (Assistant) at University of North Carolina at Chapel Hill

Somatic activating mutations in PIK3CA are common drivers of vascular and lymphatic malformations. Despite common biophysical signatures of tissues susceptible to lesion formation, including compliant extracellular matrix and low rates of perfusion, lesions vary in clinical presentation from localized cystic dilatation to diffuse and infiltrative v...

P300 is a lysine acetyltransferase that plays a significant role in regulating transcription and the nuclear acetylome. While P300 has been shown to be required for the transcription of certain early flow responsive genes, relatively little is known about its role in the endothelial response to hemodynamic fluid stress. Here we sought to define the...

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 phy...

Microphysiological and organ‐on‐chip platforms seek to address critical gaps in human disease models and drug development that underlie poor rates of clinical success for novel interventions. While the fabrication technology and model cells used to synthesize organs‐on‐chip have advanced considerably, most platforms rely on animal‐derived or synthe...

Cardiovascular 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...

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...

Exploring the pathogenesis of and developing therapies for cholestatic liver diseases such as primary sclerosing cholangitis (PSC) remains challenging, partly due to a paucity of in vitro models that capture the complex environments contributing to disease progression and partly due to difficulty in obtaining cholangiocytes. Here we report the deve...

Impaired lymphatic drainage and lymphedema are major morbidities whose mechanisms have remained obscure. To study lymphatic drainage and its impairment, we engineered a microfluidic culture model of lymphatic vessels draining interstitial fluid. This lymphatic drainage-on-chip revealed that inflammatory cytokines that are known to disrupt blood ves...

Interstitial fluid pressure gradients and interstitial flow have been shown to drive morphogenic processes that shape tissues and influence progression of diseases including cancer. The advent of porous media microfluidic approaches has enabled investigation of the cellular response to interstitial flow, but questions remain as to the critical biop...

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 E...

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease in which the bile ducts of the liver become inflamed and scarred. Scarred bile ducts eventually narrow and obstruct and can cause additional liver pathology including liver failure, repeated infections, and tumors. The pathogenesis of PSC remains largely unknown, partly due...

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...

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 E...

Cell volume is maintained by the balance of water and solutes across the cell membrane and plays an important role in mechanics and biochemical signaling in cells. Here, we assess the relationship between cell volume, mechanical properties, and E-cadherin expression in three-dimensional cultures for ovarian cancer. To determine the effect of water...

Somatic activating mutations of PIK3CA are associated with the development of vascular malformations (VMs). Here, we describe a microfluidic model of PIK3CA-driven VMs consisting of human umbilical vein endothelial cells (HUVECs) expressing PIK3CA activating mutations embedded in 3D hydrogels. We observed enlarged and irregular vessel phenotypes, c...

Integrins are surface adhesion molecules that, upon binding to ligands, cluster to form adhesion complexes. These adhesion complexes are comprised of structural and regulatory proteins that modulate a variety of cellular behaviors including differentiation, growth, and migration through bidirectional signaling activities. Aberrant integrin expressi...

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 regener...

Efficient delivery of oxygen and nutrients to tissues requires an intricate balance of blood, lymphatic, and interstitial fluid pressures, 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 si...

Cholangiopathies affect the biliary tree via various pathophysiological mechanisms. Research on biliary physiology and pathology, however, is hampered by a lack of physiologically relevant in vitro models. Conventional models, such as two-dimensional (2D) monolayers and organoids, fail to replicate the structural organization of the bile duct, and...

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 pr...

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...

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...

Objective: Perfusion models are valuable tools to mimic complex features of the tumor microenvironment and to study cell behavior. In ovarian cancer, mimicking disease pathology of ascites has been achieved by seeding tumor nodules on a basement membrane and subjecting them to long-term continuous flow. In this scenario it is particularly importan...

A major deficit in tissue engineering strategies is the lack of materials that promote angiogenesis, wherein endothelial cells from the host vasculature invade the implanted matrix to form new blood vessels. To determine the material properties that regulate angiogenesis, we have developed a microfluidic in vitro model in which chemokine-guided end...

Cardiac pacemaker cells (CPCs) rhythmically initiate the electrical impulses that drive heart contraction. CPCs display the highest rate of spontaneous depolarization in the heart despite being subjected to inhibitory electrochemical conditions that should theoretically suppress their activity. While several models have been proposed to explain thi...

Over the past decade, advances in microfabrication and biomaterials have facilitated the development of microfluidic tissue and organ models to address challenges with conventional animal and cell culture systems. These systems have largely been developed for human disease modeling and preclinical drug development and have been increasingly used to...

The mammary gland is a highly vascularized tissue capable of expansion and regression during development and disease. To enable mechanistic insight into the coordinated morphogenic crosstalk between the epithelium and vasculature, we introduce a 3D microfluidic platform that juxtaposes a human mammary duct in proximity to a perfused endothelial ves...

We appreciate the interest of Xiao et al. in our work. We believe, however, that these authors have misinterpreted our experimental design and findings. They question our conclusion that the basal surface of cholangiocyte monolayers is more sensitive to the biliary toxin biliatresone than the apical surface and raise the possibility that apical and...

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...

Angiogenesis is a complex morphogenetic process that involves intimate interactions between multicellular endothelial structures and their extracellular milieu. In vitro models of angiogenesis can aid in reducing the complexity of the in vivo microenvironment and provide mechanistic insight into how soluble and physical extracellular matrix cues re...

Targeting the tumor microenvironment (TME) provides opportunities to modulate tumor physiology, enhance the delivery of therapeutic agents, impact immune response, and overcome resistance. Photodynamic therapy (PDT) is a photochemistry‐based, non‐thermal modality that produces reactive molecular species at the site of light activation and is in the...

In this work we investigate fibroblast-enhanced tumor cell migration in an idealized tumor setting through a computational model based on a multiphase approach consisting of three phases, namely tumor cells, fibroblasts and interstitial fluid. The interaction between fibroblasts and tumor cells has previously been investigated through this model [U...

Angiogenesis is a complex morphogenetic process that involves intimate interactions between multicellular endothelial structures and their extracellular milieu. In vitro models of angiogenesis can aid in reducing the complexity of the in vivo microenvironment and provide mechanistic insight into how soluble and physical extracellular matrix cues re...

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 d...

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....

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, but barrier function is difficult to study in vivo and has not been recapitulated in vitro. Here we report the development of a bile duct-on-a-...

The architecture of individual cells and cell collectives enables functional specification, a prominent example being the formation of epithelial tubes that transport fluid or gas in many organs. The intrahepatic bile ducts (IHBDs) form a tubular network within the liver parenchyma that transports bile to the intestine. Aberrant biliary 'neoductulo...

Truncating mutations in the sarcomere protein titin cause dilated cardiomyopathy due to sarcomere insufficiency. However, it remains mechanistically unclear how these mutations decrease sarcomere content in cardiomyocytes. Utilizing human induced pluripotent stem cell-derived cardiomyocytes, CRISPR/Cas9, and live microscopy, we characterize the fun...

A major challenge in tissue engineering is the development of materials that can support angiogenesis, wherein endothelial cells from existing vasculature invade the surrounding matrix to form new vascular structures. To identify material properties that impact angiogenesis, here we have developed an in vitro model whereby molded tubular channels i...

The vascular barrier that separates blood from tissues is actively regulated by the endothelium and is essential for transport, inflammation, and haemostasis1. Haemodynamic shear stress plays a critical role in maintaining endothelial barrier function2, but how this occurs remains unknown. Here, using an engineered organotypic model of perfused mic...

Significance Organ homeostasis requires integrity of blood vessels; alterations or disruption of the vascular barrier between blood and tissue contribute to numerous diseases. Endothelial cells and mural cells are two key cell types, which play significant roles for the maintenance of barrier function. Here, we present a 3D bicellular vascular mode...

Pre-eclampsia, fetal growth restriction and stillbirth are major pregnancy disorders throughout the world. The underlying pathogenesis of these diseases is defective placentation characterized by inadequate invasion of extravillous placental trophoblast cells into the uterine arteries. How trophoblast invasion is controlled remains an unanswered qu...

Pre-eclampsia, fetal growth restriction and stillbirth are major pregnancy disorders throughout the world. The underlying pathogenesis of these diseases is defective placentation characterized by inadequate invasion of extravillous placental trophoblast cells into the uterine arteries. How trophoblast invasion is controlled remains an unanswered qu...

Ischemia-reperfusion injury (IRI) is a leading cause of AKI. This common clinical complication lacks effective therapies and can lead to the development of CKD. The αvβ5 integrin may have an important role in acute injury, including septic shock and acute lung injury. To examine its function in AKI, we utilized a specific function-blocking antibody...

Forces generated by cells are critical regulators of cell adhesion, signaling, and function, and they are also essential drivers in the morphogenetic events of development. Over the past 20 years, several methods have been developed to measure these forces. However, despite recent substantial interest in understanding the contribution of these forc...

Introduction: Dilated cardiomyopathy (DCM) is one of the most common cardiovascular disorders with a prevalence of 1:250 patients. Patients with DCM develop left ventricular dilation, systolic dysfunction, and ultimately heart failure. While DCM can occur due to acquired cardiovascular conditions, our group recently identified mutations in the gian...

Current measurements of the biomechanical properties of cells require physical contact with cells or lack subcellular resolution. Here we developed a label-free microscopy technique based on Brillouin light scattering that is capable of measuring an intracellular longitudinal modulus with optical resolution. The 3D Brillouin maps we obtained of cel...

A giant disruption of the heart Certain forms of heart failure originate from genetic mutations. Understanding how the culprit mutant proteins alter normal heart function could lead to more effective treatments. One candidate is the giant protein tintin, which is mutated in a subset of patients with dilated cardiomyopathy. Through a combination of...

Background: Cells respond to a variety of external stimuli regulated by the environment conditions. Mechanical, chemical and biological factors are of great interest and have been deeply studied. Furthermore, mathematical and computational models have been rapidly growing over the past few years, permitting researches to run complex scenarios savin...

Breast cancer incidence in the United States is I in 8, and over 90% of breast cancer related deaths are due to metastases, secondary tumors at a site distant from the primary tumor. Metastasis formation requires carcinoma cells to navigate through the tumor microenvironment and invade the surrounding stroma. Migration is a highly orchestrated proc...

Significance Interstitial flow (IF) is elevated in solid tumors and imparts fluid stresses on tumor cells within the extracellular matrix (ECM), and these fluid stresses must be balanced by stress in matrix adhesions to maintain static equilibrium. This force balance results in greater matrix adhesion tension on the upstream side of the cell, and w...

Recently, we have seen the emergence of the international laboratory in scientific research. These laboratories, characterized by internationally distributed members working to accomplish a unified goal, provide advantages such as cost savings and access to facilities and equipment. However, maintaining responsible conduct of research (RCR) in an i...

Mechanotransduction has been a topic of considerable interest since early studies demonstrated a link between mechanical force and biological response. Until recently, studies of fundamental phenomena were based either on in vivo experiments with limited control or direct access, or on large-scale in vitro studies lacking many of the potentially im...

Solid tumors are characterized by high interstitial fluid pressure, which serves as a barrier to drug delivery and an indicator for poor prognosis (Milosevic et al. Cancer Res. 2001). Elevated intratumoral fluid pressure drives fluid efflux from the tumor and high interstitial flow velocities at the tumor margin. Recently, we have demonstrated that...

In recent years, microfluidic systems have been used to study fundamental aspects of angiogenesis through the patterning of single-layered, linear or geometric vascular channels. In vivo, however, capillaries exist in complex, three-dimensional (3D) networks, and angiogenic sprouting occurs with a degree of unpredictability in all x,y,z planes. The...

Analysis of diffusion profiles in collagen and alginate-collagen gels. (a) Diffusion profiles of fluorescent tracers across collagen and (b) alginate-collagen gels, taken at 30 min intervals for 2 h as described in the Methods S1. Fluorescent tracers used were DAPI–dextran (MW 10,000) (blue), FITC–dextran (MW 40,000) (green), and Texas red–dextran...

Analysis of anastomoses on Day 4 and 5 of hMVEC sprouting. Phase contrast images taken on (a) Day 4 and (c) Day 5 show that the sprouts are invading the collagen-alginate gels. Identical phase contrast images taken on (b) Day 4 and (d) Day 5 are reproduced with additional markings to show the pattern of the sprouts (red) and points of contact (yell...

Time-lapse imaging of the initial hMVEC sprout formation. hMVEC sprout formation is a dynamic process, and here a single hMVEC sprout probes the 3D gel matrix by sending its filopodia in two directions from the confluent monolayer interface, before retracting the sprout. Images were taken using phase contrast microscopy at 10× magnification in 50 m...

Cellular protein expression. (a) Phase contrast images of cells from a HT-1080 human fibrosarcoma cell line and human dermal fibroblasts (HDF). (b) Cellular proliferation of HT-1080 versus HDF cells over 72 h. (c) Protein expression levels of VEGF, (d) angiogenin, and (e) PIGF, tested by an angiogenesis antibody array as described in the Methods S1...

3D reconstruction of a microvascular network z-stack. Microvascular networks were imaged by confocal microscopy at 40× magnification. Devices were fixed and immunofluorescently labeled to detect vascular networks: VE-cadherin on cell membranes (anti-VE-cadherin antibody, green), cytoplasmic actin (rhodamine-phalloidin, red), and cell nuclei (DAPI,...

Time-lapse imaging of flow through 3D capillary bed. The flow of fluorescent 1 µm diameter beads through the 3D capillary bed was imaged using time-lapse fluorescence microscopy at 10× magnification. After imaging, devices were fixed and immunofluorescently labeled to detect vascular networks: VE-cadherin on cell membranes (anti-VE-cadherin antibod...

Supporting Methods. (DOC)

Tumor cell migration is essential for invasion and dissemination from primary solid tumors and for the establishment of lethal secondary metastases at distant organs. In vivo and in vitro models enabled identification of different factors in the tumor microenvironment that regulate tumor progression and metastasis. However, the mechanisms by which...

Adipose progenitor cells (APCs) are widely investigated for soft tissue reconstruction following tumor resection; however, the long-term success of current approaches is still limited. In order to develop clinically relevant therapies, a better understanding of the role of cell-microenvironment interactions in adipose tissue regeneration is essenti...

Interstitial flow is the convective transport of fluid through tissue extracellular matrix. This creeping fluid flow has been shown to affect the morphology and migration of cells such as fibroblasts, cancer cells, endothelial cells, and mesenchymal stem cells. A microfluidic cell culture system was designed to apply stable pressure gradients and f...

Interstitial flow is the convective transport of fluid through tissue extracellular matrix. This creeping fluid flow has been shown to affect the morphology and migration of cells such as fibroblasts, cancer cells, endothelial cells, and mesenchymal stem cells. However, due to limitations in experimental procedures and apparatuses, the mechanism by...

Methods for seeding high-viability (>85%) three-dimensional (3D) alginate-chondrocyte hydrogel scaffolds are presented that employ photocrosslinking of methacrylate-modified alginate with the photoinitiator VA-086. Comparison with results from several other photoinitiators, including Irgacure 2959, highlights the role of solvent, ultraviolet exposu...

Interstitial flow is the convective transport of fluid through tissue extracellular matrix. This creeping fluid flow has been shown to be important in regulating the development, function, and pathology of tissues. Furthermore, interstitial flow has been shown to affect the morphology and migration of cells such as fibroblasts, cancer cells, endoth...

Interstitial flow is the convective transport of fluid through tissue extracellular matrix. This creeping fluid flow has been shown to be important in regulating the development, function, and pathology of tissues. Furthermore, interstitial flow has been shown to affect the morphology and migration of cells such as fibroblasts, cancer cells, endoth...