[HTML][HTML] CHD4-regulated plasmin activation impacts lymphovenous hemostasis and hepatic vascular integrity

PL Crosswhite, JJ Podsiadlowska… - The Journal of …, 2016 - Am Soc Clin Investig
PL Crosswhite, JJ Podsiadlowska, CD Curtis, S Gao, L Xia, RS Srinivasan, CT Griffin
The Journal of Clinical Investigation, 2016Am Soc Clin Investig
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 …
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.
The Journal of Clinical Investigation