title: Transient Intervals of Hyper-Gravity Enhance Endothelial Barrier Integrity: Impact of Mechanical and Gravitational Forces Measured Electrically.
abstract: BACKGROUND
  Endothelial cells (EC) guard vascular functions by forming a dynamic barrier throughout the vascular system that sensitively adapts to 'classical' biomechanical forces, such as fluid shear stress and hydrostatic pressure. Alterations in gravitational forces might similarly affect EC integrity, but remain insufficiently studied.
  
  
  METHODS
  In an unique approach, we utilized Electric Cell-substrate Impedance Sensing (ECIS) in the gravity-simulators at the European Space Agency (ESA) to study dynamic responses of human EC to simulated micro- and hyper-gravity as well as to classical forces.
  
  
  RESULTS
  Short intervals of micro- or hyper-gravity evoked distinct endothelial responses. Stimulated micro-gravity led to decreased endothelial barrier integrity, whereas hyper-gravity caused sustained barrier enhancement by rapid improvement of cell-cell integrity, evidenced by a significant junctional accumulation of VE-cadherin (p = 0.011), significant enforcement of peripheral F-actin (p = 0.008) and accompanied by a slower enhancement of cell-matrix interactions. The hyper-gravity triggered EC responses were force dependent and nitric-oxide (NO) mediated showing a maximal resistance increase of 29.2±4.8 ohms at 2g and 60.9±6.2 ohms at 4g vs. baseline values that was significantly suppressed by NO blockage (p = 0.011).
  
  
  CONCLUSIONS
  In conclusion, short-term application of hyper-gravity caused a sustained improvement of endothelial barrier integrity, whereas simulated micro-gravity weakened the endothelium. In clear contrast, classical forces of shear stress and hydrostatic pressure induced either short-lived or no changes to the EC barrier. Here, ECIS has proven a powerful tool to characterize subtle and distinct EC gravity-responses due to its high temporal resolution, wherefore ECIS has a great potential for the study of gravity-responses such as in real space flights providing quantitative assessment of a variety of cell biological characteristics of any adherent growing cell type in an automated and continuous fashion.
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands.|Department of Pulmonology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Robert
authors.initials: R
authors.lastname: Szulcek
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Jan
authors.initials: J
authors.lastname: van Bezu
authors.affiliation: Deptartment of Cellular Architecture and Dynamics, Science Faculty, Utrecht University, Utrecht, The Netherlands.
authors.forename: Johannes
authors.initials: J
authors.lastname: Boonstra
authors.affiliation: Dutch Experiment Support Center (DESC), ESTEC, TEC-MMG-Lab, European Space Agency (ESA), Noordwijk, The Netherlands.|Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center, Amsterdam, The Netherlands.|Department of Oral Cell Biology, Academic Centre for Dentistry (ACTA), Amsterdam, The Netherlands.
authors.forename: Jack J W A
authors.initials: JJ
authors.lastname: van Loon
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Geerten P
authors.initials: GP
authors.lastname: van Nieuw Amerongen
mesh_terms: D017097:Electric Impedance; D005109:Extracellular Matrix / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D018471:Hypergravity; D009569:Nitric Oxide / Q000378:metabolism*
chemical_list: D009569:Nitric Oxide