Separation of blood and lymphatic vessels requires the hematopoietic signaling proteins SYK and SLP-76, but how blood cells perform this function is not known. Using genetic approaches in mice we have recently identified platelets as the cell type required for blood-lymphatic separation. Genetic fate-mapping studies exclude hematopoietic cell contribution to vascular endothelium during this process, while transgenic expression of SLP-76 in GATA1+ lineages including platelets restores blood-lymphatic separation in SLP-76- deficient animals. Conditional deletion of Slp-76 specifically in platelets is sufficient to confer vascular mixing. We find that Podoplanin (PDPN), a cell surface protein expressed specifically by lymphatic endothelium, is required in a common pathway with SLP-76 during vascular separation. PDPN activates platelets and we detect platelet micro-thrombi on lymphatic endothelium during blood flow ex vivo and at blood-lymphatic separation points in the developing mouse embryo. These studies reveal a previously un-appreciated non- hemostatic role for circulating blood platelets in mediating vascular separation and an unexpected mechanism by which lymphatic vessel growth and development is regulated. Platelets are anuclear blood cells that mediate hemostasis following vessel injury and form the thrombi that underlie stroke and heart attacks. How platelets regulate lymphatic endothelial growth and development is unknown and this proposal will address this question using both in vivo and ex vivo approaches. These studies will explore a completely new cellular and molecular pathway that links lymphatic vascular biology to the blood vascular system and hemostasis with important implications for blood and lymphatic vascular human diseases.

Public Health Relevance

This proposal will investigate how platelets regulate the growth of lymphatic vessels. Our findings linking a cell type previously connected only to blood clotting to lymphatic vessel growth is unexpected and suggests an important connection between these different biological processes. Since both lymphatic vessel defects and platelet activation are responsible for human vascular diseases we expect these studies to provide new insight into human disease.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL103432-03
Application #
8286194
Study Section
Special Emphasis Panel (ZRG1-CVRS-F (50))
Program Officer
Tolunay, Eser
Project Start
2010-07-01
Project End
2014-05-31
Budget Start
2012-06-01
Budget End
2013-05-31
Support Year
3
Fiscal Year
2012
Total Cost
$396,000
Indirect Cost
$148,500
Name
University of Pennsylvania
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Hess, Paul R; Rawnsley, David R; Jakus, Zoltan et al. (2014) Platelets mediate lymphovenous hemostasis to maintain blood-lymphatic separation throughout life. J Clin Invest 124:273-84
Herzog, Brett H; Fu, Jianxin; Wilson, Stephen J et al. (2013) Podoplanin maintains high endothelial venule integrity by interacting with platelet CLEC-2. Nature 502:105-9
Stanger, Ben Z; Kahn, Mark L (2013) Platelets and tumor cells: a new form of border control. Cancer Cell 24:9-11
Boulaftali, Yacine; Hess, Paul R; Getz, Todd M et al. (2013) Platelet ITAM signaling is critical for vascular integrity in inflammation. J Clin Invest 123:908-16
Bertozzi, Cara C; Hess, Paul R; Kahn, Mark L (2010) Platelets: covert regulators of lymphatic development. Arterioscler Thromb Vasc Biol 30:2368-71