Secret alter ego of well-known protein fights leaky blood vesselsNovember 13, 2017
(BOSTON) -- With every heartbeat, a gallon and a half of blood pulses through the body's network of veins and arteries. The force of that blood flow helps keep the cells that line the blood vessels, called endothelial cells, healthy; when blood flow is disrupted, such as during surgical procedures or a stroke, the vessels start to leak, which can cause a host of inflammatory responses that lead to cell damage and disease. Scientists at the Wyss Institute at Harvard University set out to solve the mystery of how blood flow keeps the vessels intact and, to their surprise, discovered a completely new cell signaling pathway that is a promising target for drugs to treat a variety of debilitating conditions.
"We found that the well-known Notch protein is responsible for keeping blood vessels from becoming leaky, and does so through a secondary signaling pathway that operates in a completely different manner than its known transcription-based pathway," says Chris Chen, M.D., Ph.D., Associate Faculty member of the Wyss Institute and Professor of Biomedical Engineering at Boston University, who is the corresponding author of the paper. "Not only is this new pathway exciting from a discovery perspective, it could ameliorate some of the side effects of cancer and cardiovascular drugs to make them safer and more effective." The study is published today in Nature.
The endothelial cells that line blood vessels are linked tightly together through connections called adherens junctions to form a barrier that keeps the blood inside the vessel and regulates how easily other substances can pass in and out of it. To study this barrier and determine why a lack of blood flow causes it to leak, the researchers built a blood-vessel-on-a-chip model consisting of a channel lined with a layer of human endothelial cells surrounded by extracellular matrix within a microfluidic device, which allowed them to easily simulate and control the flow of blood through a vessel and evaluate the cells' responses.
Endothelial cells that experienced blood flow displayed increased activity of the transmembrane protein Notch1, while cells exposed to static blood did not. When the researchers added a chemical that blocks Notch1 activation, they observed that the vessel started to leak, which they determined to be caused by the disruption of adherens junctions between neighboring endothelial cells and the reorganization of actin fibers within each cell, confirming that activation of Notch1 by blood flow is necessary for the formation and maintenance of blood vessels' endothelial barrier.
Curiously, blocking Notch1's known mechanism of action - the detachment of its intracellular domain from the rest of the protein - did not make the vessels leak, which implied that some other part of the protein was responding to blood flow. This suspicion was strengthened by in vivo experiments in which the scientists injected mice with a chemical that blocked Notch1 activation along with blue dye, and saw that the dye leaked out of the blood vessels of treated mice at a much faster rate than expected. "[The intracellular domain's function of] transcribing a gene into a protein that then performs some function within the cell generally takes about two hours, but we were seeing leakage within 30 minutes of blocking Notch1, further suggesting that whatever process controls the permeability of the barrier is operating via a completely different mechanism," says Bill Polacheck, Ph.D., Postdoctoral Fellow at the Wyss Institute and co-first author of the paper.
Once they established that the intracellular domain was not involved in regulating the endothelial barrier, the scientists scanned other parts of Notch1 for activity. They used CRISPR/Cas-9 to delete various sections of the Notch1 gene, and found that deleting the section that codes for the intracellular domain had no effect on permeability, while deleting the section that codes for the tiny transmembrane domain (TMD) caused vessel leakage to increase under flow conditions. "This is the first time the biological function of the Notch TMD has ever been evaluated," says Matthew Kutys, Ph.D., a Visiting Fellow at the Wyss Institute and co-first author. "It was largely assumed to be inert and just kind of disappear after activation, and most textbooks and research papers don't even show it as a distinct portion of Notch receptors." Through further testing, they figured out that when Notch1 is activated and its intracellular domain is released, its TMD assembles a complex in the membrane with the proteins VE-cadherin, Rac1, LAR, and Trio, which collectively assemble and maintain the adherens junctions between cells and distribute actin fibers against the cell membrane to support those junctions.
"In retrospect, we rolled the dice with this project, because by choosing to investigate Notch we were entering one of the most crowded research areas in biology. But our engineering-based approach let us study it in a new way, without the influence or bias of past work, which I think is what made us open-minded enough to observe and characterize this new, unexpected pathway," says Polacheck. "Knowing that Notch1 regulates cell adhesion [through the new TMD-controlled pathway] in addition to cell differentiation [through its previously described transcription pathway] also offers a new framework for understanding the coordination of complex cellular processes, in that single molecules like Notch can play multiple roles," adds Kutys.
The revelation that Notch1 serves different functions, and knowing which parts of the protein govern each function, allows for the development of new drugs that are both more effective and less toxic. "Notch is a target for some cancer therapies, but those drugs are known to cause edema [the collection of fluid in the body] and other problems. Now, we're actively working on separating Notch's two pathways so that we can create drugs that target the intracellular domain alone, sparing the TMD and thus preserving the integrity of the blood vessels," says Karen Hirschi, Ph.D., Professor of Medicine and Genetics at the Yale School of Medicine, who collaborated on the study. Knowing that Notch governs vessel permeability makes it a candidate for new drugs to treat cardiovascular diseases as well, and the team is also investigating the TMD as a potential therapeutic agent itself, as cell models that were exposed to leak-inducing inflammation displayed a dramatic reduction in leakage when they were engineered to express the TMD.
"The collaborations that the Wyss Institute enables and nurtures between disparate fields, like mechanical engineering and molecular biology, foster new approaches to old problems that can lead to truly paradigm-shifting results," says Donald Ingber, M.D. Ph.D., the Founding Director of the Wyss Institute and the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children's Hospital, who is also a Professor of Bioengineering at the Harvard Paulson School of Engineering and Applied Sciences (SEAS). "This study is a prime example of the benefits these types of partnerships can provide to science and society."
The Wyss Institute for Biologically Inspired Engineering at Harvard University uses Nature's design principles to develop bioinspired materials and devices that will transform medicine and create a more sustainable world. Wyss researchers are developing innovative new engineering solutions for healthcare, energy, architecture, robotics, and manufacturing that are translated into commercial products and therapies through collaborations with clinical investigators, corporate alliances, and formation of new startups. The Wyss Institute creates transformative technological breakthroughs by engaging in high risk research, and crosses disciplinary and institutional barriers, working as an alliance that includes Harvard's Schools of Medicine, Engineering, Arts & Sciences and Design, and in partnership with Beth Israel Deaconess Medical Center, Brigham and Women's Hospital, Boston Children's Hospital, Dana-Farber Cancer Institute, Massachusetts General Hospital, the University of Massachusetts Medical School, Spaulding Rehabilitation Hospital, Boston University, Tufts University, Charité - Universitätsmedizin Berlin, University of Zurich and Massachusetts Institute of Technology.
Founded in 1839, Boston University is an internationally recognized institution of higher education and research. With more than 33,000 students, it is the fourth-largest independent university in the United States. BU consists of 17 schools and colleges, along with a number of multi-disciplinary centers and institutes integral to the University's research and teaching mission. In 2012, BU joined the Association of American Universities (AAU), a consortium of 62 leading research universities in the United States and Canada.
Wyss Institute for Biologically Inspired Engineering at Harvard
Related Blood Vessels Articles:
Researchers at OHSU in Portland, Oregon, have developed a process by which they can engineer new blood vessels in teeth, creating better long-term outcomes for root canal patients and clinicians.
In diseases like cancer, diabetes, rheumatism and stroke, a disorder develops in the blood vessels that exacerbates the condition and obstructs treatment.
EPFL scientists have improved the efficacy of cancer immunotherapy by blocking two proteins that regulate the growth of tumor blood vessels.
Tumor cells use the bloodstream to spread in the body.
A team of researchers at Karlsruhe Institute of Technology shake at the foundations of a dogma of cell biology.
The PIEZO1 cation channel translates mechanical stimulus into a molecular response to control the diameter of blood vessels.
Blood vessels play a vital role in stem cell reproduction, enabling the brain to grow and develop in the womb, reveals new UCL research in mice.
After 20 years of searching, scientists discover the mystic gene controlling vessel and blood cell growth in the embryo.
Growing tissues and organs in the lab for transplantation into patients could become easier after scientists discovered an effective way to produce three-dimensional networks of blood vessels, vital for tissue survival yet a current stumbling block in regenerative medicine.
Biomedical engineers in the Cockrell School of Engineering at The University of Texas at Austin have received $2.7 million in funding to advance a treatment that regenerates blood vessels.
Related Blood Vessels Reading:
The Fluid Mechanics of Large Blood Vessels (Cambridge Monographs on Mechanics)
by T. J. Pedley (Author)
The analysis of the circulation of the blood is one of the most important areas of fluid mechanics research, with far-reaching medical and physiological implications. View Details
Blood Vessels like a Teenager: Insider-cures against atherosclerosis
by Christian Meyer-Esch (Author)
Many people in the western world suffer from massive circulatory disorders due to obstructed blood vessels. In this book, you will learn how exactly these deposits are formed, what kind of deposits there are, and how to avoid them, but also to easily resolve them. Any claims are proven by scientific studies. After reading this book, you will be an expert on blood vessels. They will have knowledge about what doctors have not usually been taught in medicine. Again, clean blood vessels of a teenager! To treat and prevent heart attack, stroke and circulatory disorders. With my new immediate... View Details
Inflammatory Diseases of Blood Vessels
by Gary S. Hoffman (Editor), Cornelia M. Weyand (Editor), Carol A. Langford (Editor), Jorg J. Goronzy (Editor)
In recent years, considerable progress has been made in understanding the vasculitic diseases, largely due to the introduction of effective treatments for diseases that were once uniformly fatal, the conduct of structured clinical studies, and advances in immunology and molecular biology. Despite these achievements, the vasculitic diseases continue to be associated with morbidity and mortality from chronic organ damage, relapses, and the side effects of treatment. Investigations into the mechanisms of vascular inflammation may lead to a better comprehension of the pathogenesis of vasculitic... View Details
Managing Type 2 Diabetes For Dummies
by American Diabetes Association (Author)
Discover how to manage diabetes for a healthier and happier life!
Written for anyone diagnosed with type 2 diabetes (and for anyone who loves someone with diabetes), Managing Type 2 Diabetes For Dummies is an essential guide to understanding the effects of diabetes and knowing what steps to take to successfully manage this chronic illness. Diabetes can lead to serious complications but people with diabetes can control the condition and lower the risk of its many complications. This is your easy-to-understand guide that shows you how. Under the direction of The... View Details
LIPITOR (Atorvastatin): Treats High Cholesterol and Triglyceride Levels; and Reduces the Risk of Angina, Stroke, Heart Attack, or Certain Heart and Blood Vessel Problems
by James Lee Anderson (Author)
“Although, your health condition may impact your everyday life, do not let it define who you are.” LIPITOR (atorvastatin) is used together with diet, weight loss, and exercise to reduce the risk of heart attack and stroke and to decrease the chance that heart surgery will be needed in people who have heart disease or who are at risk of developing heart disease. LIPITOR (atorvastatin) is also used to decrease the amount of fatty substances such as low-density lipoprotein (LDL) cholesterol ('bad cholesterol') and triglycerides in the blood and to increase the amount of high-density... View Details
Human Body! (Knowledge Encyclopedias)
by DK (Author)
The ultimate kids' guide to the human body, with computer-generated 3-D imagery that shows them the body as they've never seen it before, from the award-winning publisher of Knowledge Encyclopedia.
This visual encyclopedia includes astonishing, all-new 3-D artworks, offering a fascinating view of every part of the body from the skull to the heart and lungs to the joints and muscles, taking kids from head to toe. Supporting STEM education initiatives, all the body systems and structures are made easy to understand. Both the anatomy—how the body looks—and the... View Details
Pathology of the cerebral blood vessels
by William E Stehbens (Author)
vi 661p large format hardback, blue cloth with dark title label, gilt lettering, plates throughout, a very heavy and solid book, excellent condition, 322 illustrations View Details
Little Book for Heart and Blood Vessel Health: What is my risk for heart attack or another vascular event? How do I achieve goal?
by Philip H. Frost M.D. (Author)
The premise of this Little Book is that the learned individual will be motivated to seek assistance in reducing his/her risk of suffering a vascular event. This book provides the reader with language to understand lipid measurements, background to consider risk assessment, lipid goals, and tools currently available to achieve risk factor reduction. Patient stories illustrate not only the myriad of problems that are encountered, but methods employed to achieve success - ideal lipids. View Details
Study Guide for Human Anatomy and Physiology: Endocrine System, Blood Vessels, Blood Flow and Heart
by Dr Evelyn J Biluk (Author)
This is a collection of multiple choice questions on the endocrine system, blood vessels, blood flow and the heart. Topics covered include an overview of the endocrine system, endocrine glands, hormone activity, hormone action, hormone secretion, hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, testes, pineal gland, thymus, blood vessels, blood flow, blood pressure, circulation, shock, circulation routes, cardiac muscle tissue, heart anatomy, heart valves, circulation, conduction system, cardiac cycle, cardiac output, and exercise. These... View Details
Horse Anatomy (Dover Nature Coloring Book)
by John Green (Author)
This incredibly detailed coloring book examines the external and internal anatomy of the horse, with 30 pages of accurate drawings highlighting the skeleton, muscles, nervous system, and major organs, including internal organs and the organs of locomotion. All illustrations are clearly labeled and explained. Also included are notes on the evolution of the horse as well as general health and care issues. An excellent introduction for horse lovers of all ages. View Details