CHD4-regulated Plasmin Activation Impacts Lymphovenous Hemostasis and Hepatic Vascular Integrity

J Clin Invest. 2016 Jun 1;126(6):2254-66. doi: 10.1172/JCI84652. Epub 2016 May 3.

Abstract

The chromatin-remodeling enzyme CHD4 maintains vascular integrity at mid-gestation; however, it is unknown whether this enzyme contributes to later blood vessel or lymphatic vessel development. Here, we addressed this issue in mice harboring a deletion of Chd4 specifically in cells that express lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1), which include lymphatic endothelial cells (LECs) and liver sinusoidal endothelial cells. Chd4 mutant embryos died before birth and exhibited severe edema, blood-filled lymphatics, and liver hemorrhage. CHD4-deficient embryos developed normal lymphovenous (LV) valves, which regulate the return of lymph to the blood circulation; however, these valves lacked the fibrin-rich thrombi that prevent blood from entering the lymphatic system. Transcripts of the urokinase plasminogen activator receptor (uPAR), which facilitates activation of the fibrin-degrading protease plasmin, were upregulated in Chd4 mutant LYVE1+ cells, and plasmin activity was elevated near the LV valves. Genetic reduction of the uPAR ligand urokinase prevented degradation of fibrin-rich thrombi at the LV valves and largely resolved the blood-filled lymphatics in Chd4 mutants. Urokinase reduction also ameliorated liver hemorrhage and prolonged embryonic survival by reducing plasmin-mediated extracellular matrix degradation around sinusoidal blood vessels. These results highlight the susceptibility of LV thrombi and liver sinusoidal vessels to plasmin-mediated damage and demonstrate the importance of CHD4 in regulating embryonic plasmin activation after mid-gestation.

MeSH terms

  • Animals
  • DNA Helicases / deficiency
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • Enzyme Activation
  • Female
  • Fibrinolysin / metabolism*
  • Glycoproteins / deficiency
  • Glycoproteins / genetics
  • Glycoproteins / metabolism
  • Hemostasis / genetics
  • Hemostasis / physiology
  • Liver / blood supply*
  • Liver / embryology*
  • Liver / metabolism
  • Lymphangiogenesis / genetics
  • Lymphatic Vessels / abnormalities
  • Lymphatic Vessels / embryology*
  • Lymphatic Vessels / metabolism
  • Membrane Transport Proteins
  • Mice
  • Mice, Knockout
  • Neovascularization, Physiologic / genetics
  • Pregnancy
  • Receptors, Urokinase Plasminogen Activator / genetics
  • Receptors, Urokinase Plasminogen Activator / metabolism
  • Up-Regulation

Substances

  • Glycoproteins
  • Membrane Transport Proteins
  • Plaur protein, mouse
  • Receptors, Urokinase Plasminogen Activator
  • Xlkd1 protein, mouse
  • Fibrinolysin
  • Mi-2beta protein, mouse
  • DNA Helicases