Platelets mediate lymphovenous hemostasis to maintain blood-lymphatic separation throughout life
Paul R. Hess, … , Lijun Xia, Mark L. Kahn
Paul R. Hess, … , Lijun Xia, Mark L. Kahn
Published December 2, 2013
Citation Information: J Clin Invest. 2014;124(1):273-284. https://doi.org/10.1172/JCI70422.
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Research Article Hematology

Platelets mediate lymphovenous hemostasis to maintain blood-lymphatic separation throughout life

Abstract

Mammals transport blood through a high-pressure, closed vascular network and lymph through a low-pressure, open vascular network. These vascular networks connect at the lymphovenous (LV) junction, where lymph drains into blood and an LV valve (LVV) prevents backflow of blood into lymphatic vessels. Here we describe an essential role for platelets in preventing blood from entering the lymphatic system at the LV junction. Loss of CLEC2, a receptor that activates platelets in response to lymphatic endothelial cells, resulted in backfilling of the lymphatic network with blood from the thoracic duct (TD) in both neonatal and mature mice. Fibrin-containing platelet thrombi were observed at the LVV and in the terminal TD in wild-type mice, but not Clec2-deficient mice. Analysis of mice lacking LVVs or lymphatic valves revealed that platelet-mediated thrombus formation limits LV backflow under conditions of impaired valve function. Examination of mice lacking integrin-mediated platelet aggregation indicated that platelet aggregation stabilizes thrombi that form in the lymphatic vascular environment to prevent retrograde blood flow. Collectively, these studies unveil a newly recognized form of hemostasis that functions with the LVV to safeguard the lymphatic vascular network throughout life.

Authors

Paul R. Hess, David R. Rawnsley, Zoltán Jakus, Yiqing Yang, Daniel T. Sweet, Jianxin Fu, Brett Herzog, MinMin Lu, Bernhard Nieswandt, Guillermo Oliver, Taija Makinen, Lijun Xia, Mark L. Kahn

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Figure 1

Loss of CLEC2 results in blood-filled lymphatics in the intestine of both perinatal and mature mice.

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Loss of CLEC2 results in blood-filled lymphatics in the intestine of bot...
(A) Genetic deletion of Clec2 resulted in blood-filled lymphatics in the skin at midgestation (top) and in the small intestine at birth (bottom). (B and C) Mature wild-type mice reconstituted with Clec2–/– hematopoietic cells exhibited blood-filled intestinal lymphatics (B) and large, bloody pleural effusions (C). (B) Images of the intestine were obtained 5.5 weeks after transplantation of the indicated hematopoietic cells. Respiratory distress and death were observed in animals with Clec2–/–, but not Clec2+/+ or Clec2+/–, hematopoietic cells. (C) Pleural effusion fluid was obtained at the time of sacrifice. The survival curve of a transplantation cohort is also shown. A large pleural effusion was observed in all 6 Clec2–/– recipients. (D) i.p. injection of the anti-CLEC2 antibody INU1 at P1 resulted in a sustained CLEC2 deficiency state. Shown is flow cytometry of circulating platelets stained with anti-CLEC2 or anti-GP1b antibodies. (E) INU1-mediated CLEC2 deficiency conferred blood-filled intestinal lymphatics. Images of intestine at P5, after a single INU1 injection at P1 (left), or at P14, after injection at P1, P5, and P9 (middle and right). Arrows indicate lymphatic vessels. Boxed regions are shown at higher magnification (enlarged ×3). V, vein; A, artery, L, lymphatic.