The Influence of Mechanical Signal on the Endothelial to Mesenchymal Transition in Human Pulmonary Microvascular Endothelial Cells

Open Access
Author:
Johnson, Kaitlyn Meghan
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Esther Winter Gomez, Thesis Supervisor
  • Michael John Janik, Honors Advisor
Keywords:
  • endothelial
  • mesenchymal
  • transition
  • transforming growth factor beta
  • pulmonary fibrosis
  • pulmonary hypertension
Abstract:
The purpose of this paper was to study the effects of mechanical signals on the endothelial-to-mesenchymal transition (EndMT) of Human Pulmonary Microvascular Endothelial Cells (HPMEC). This transition has been linked to the development of pulmonary fibrosis and diseases of the vasculature such as pulmonary hypertension in humans. This transition is characterized by the endothelial cell’s loss of cell-to-cell junctions, loss of endothelial markers and gain of mesenchymal characteristics including increased contractility and motility. Specifically examined was how the stiffness of the environment, in which the cells grow, affects this transition. The examined range of stiffnesses models the different stiffnesses of tissue found in the lung vasculature of humans. Various proteins found within endothelial cells, like VE-Cadherin, were examined under both normal conditions and after treatment with transforming growth factor beta (TGF-ß), an inducer of EndMT. In order to analyze EndMT, HPMECs were plated onto polyacrylamide gels of varying elasticities, and then EndMT was induced through treatment with TGF- ß. Various proteins in both the control cells and those that have been treated with TGF-ß were analyzed through techniques such as immunofluorescence staining and western blotting. The expression and localization of the endothelial marker VE-cadherin was found to decrease in TGF-β treated cells grown on a stiff substrate. Additionally, cell spread area increased as a function of cell environment rigidity and all TGF-β treated samples exhibited a higher cell spread area compared to the control samples. It was further determined that as rigidity of the environment increased, the expression of the mesenchymal marker α-SMA increased as well.