Download Platelets - Arteriosclerosis, Thrombosis, and Vascular Biology

ATVB in Focus
Platelets Unplugged: Focus on Platelet Biology
Series Editor: Susan S. Smyth
Platelets
Covert Regulators of Lymphatic Development
Cara C. Bertozzi, Paul R. Hess, Mark L. Kahn
Downloaded from http://atvb.ahajournals.org/ by guest on May 3, 2017
Abstract—The field of platelet biology has rapidly expanded beyond the classical role of platelets in preventing blood loss
and orchestrating clot formation. Despite the lack of transcriptional ability of these anuclear cell fragments, platelet
function is now thought to encompass such diverse contexts as tissue repair, immune activation, primary tumor
formation, and metastasis. Recent studies from multiple groups have turned the spotlight on an exciting new role for
platelets in the formation of lymphatic vessels during embryonic development. Genetic experiments demonstrate that
Podoplanin, a transmembrane protein expressed on lymphatic endothelial cells, engages the platelet C-type lectin-like
receptor 2 (CLEC-2) when exposed to blood, leading to SYK-SLP-76-dependent platelet activation. When components
of this pathway are disrupted, aberrant vascular connections form, resulting in blood-lymphatic mixing. Furthermore,
platelet-null embryos manifest identical blood-lymphatic mixing. The identification of platelets as the critical cell type
mediating blood-lymphatic vascular separation raises new questions in our understanding of lymphatic development and
platelet biology. (Arterioscler Thromb Vasc Biol. 2010;30:2368-2371.)
Key Words: platelets 䡲 vascular biology 䡲 lymphatics
H
Lymphatic Development
ematopoiesis and vascular development have shared
origins, as progenitors of both lineages initially arise in
extraembryonic blood islands. In the embryo, endothelial
precursors surround clusters of primitive hematopoietic precursors before vascular lumen formation.1 Definitive hematopoietic stem cells subsequently arise from a subset of
competent endothelial cells of the dorsal aorta in the aortagonad-mesonephros region of the developing embryo.2,3
There has been a long and heated debate over the contribution
of bone marrow– derived cells to endothelium during development that has been complicated by the close spatiotemporal
association and common molecular markers between the 2
lineages. Fatemapping studies conducted in blood vessels
using Vav-Cre transgenic mice4 and in lymphatic vessels
using Runx1-MER-Cre-MER inducible knock-in mice5
showed that most, if not all, endothelial cells are not of
hematopoietic origin. However, the distinct blood-lymphatic
mixing vascular phenotype in mice lacking the hematopoietic
proteins SYK or SLP-76 suggested that there could be a small
but critical requirement for bone marrow– derived endothelium.
This review will highlight definitive evidence that SYK/
SLP-76 knockout vascular abnormalities do not arise from a
failure of bone marrow– derived cells to incorporate into the
vasculature but rather from the requirement of hematopoietic
cells, specifically platelets, to regulate blood-lymphatic separation. We present contributions by a number of groups that
describe the discovery of a novel embryonic role for platelets
in regulating vascular development.
Lymphatic vessels form an extensive vascular network that
facilitates immune trafficking and surveillance, maintains
tissue fluid homeostasis, and absorbs dietary lipids in the
intestine through mesenteric lacteals.6 These specialized vessels are composed of lymphatic endothelial cells (LECs) that
originate in the cardinal vein as venous endothelial cells.
Starting at embryonic day (E) 9.75, polarized induction of
PROX1, a homeobox transcription factor, is necessary and
sufficient to activate the lymphatic gene profile.5,7 These
LECs then migrate away from the cardinal vein, largely in
response to vascular endothelial growth factor receptor-3/
Neuropilin-2 signaling induced by vascular endothelial
growth factor-C in the mesoderm.8 The LECs assemble into
vessels to form a de novo collecting system, parallel to but
separate from the blood vessels, sprouting centrifugally from
the initial sacs and migrating deeper into tissues to form the
inner lymphatic plexus.5 The resulting collecting vessels form
luminal valves to prevent backflow and are covered by mural
cells, whereas the blind-ended capillaries lack mural cells and
remain largely uninvested by pericytes. Lymphatic capillary
endothelium is characterized by loose intercellular junctions
that facilitate the homeostatic function of these vessels.
A careful kinetic study of murine intestinal lymphatic
development reveals that mature blood vessels are established
days before lymphatics invade the mesentery and the intestinal tube. By E13.5 to E14.5, although local blood vessel
Received on: September 27, 2010; final version accepted on: October 6, 2010.
From the Department of Medicine and Cardiovascular Institute, University of Pennsylvania, Philadelphia Pa.
Correspondence to Mark L. Kahn, Department of Medicine and Cardiovascular Institute, University of Pennsylvania, 421 Curie Blvd, Philadelphia PA
19104. E-mail [email protected]
© 2010 American Heart Association, Inc.
Arterioscler Thromb Vasc Biol is available at http://atvb.ahajournals.org
2368
DOI: 10.1161/ATVBAHA.110.217281
Bertozzi et al
Platelets: Regulators of Lymphatic Development
2369
development is complete, there are few or no lymphatics in
the wall of the small intestine, and immature lymphatics have
just begun to invade the mesentery. By E16.5, there has been
a remarkable increase in branching and further migration into
the intestinal tube, but it is not until E19.5 that they have
formed a mature lymphatic network capable of transporting
the large amounts of fat required for nutritional absorption.9
The completed vascular and lymphatic endothelial networks
connect only at the thoracic duct in the mouse, where the
collected lymphatic fluid is returned to the blood circulation
through the subclavian vein.5,10,11
suggesting a hematopoietic requirement for normal lymphatic
development.5 Careful analysis of hematopoietic lineage
tracing using a Runx1-MER-Cre-MER inducible knock-in
mouse17 to examine the emerging lymphatic endothelial sacs
failed to reveal any direct contribution of bone marrow–
derived cells to these vessels. 5 Finally, although
hematopoietic-specific deletion of SLP-76 using Vav-Cre
confers the vascular phenotypes seen in the straight knockout,
lineage tracing in these mice also failed to demonstrate any
hematopoietic origin of LECs, even in the highly affected gut,
where the requirement is greatest.18
Blood-Lymphatic Mixing
Loss of Podoplanin on LECs Leads to
Blood-Lymphatic Mixing
Downloaded from http://atvb.ahajournals.org/ by guest on May 3, 2017
Mice lacking SYK,12,13 SLP-76,14 or PLC␥-215 develop
blood-lymphatic mixing in distinct vascular beds at specific
time points during embryonic development. This is the result
of primary misconnections between lymphatics and blood
vessels.14 Disruptions in normal development are first detectable at E11.5 as the nascent lymphatic sacs are emerging from
the cardinal vein along the antero-posterior axis of the
embryo. Small connections between lymphatic and venous
endothelial cells persist along the cardinal vein in the mutant
mice, resulting in downstream filling of the superficial dermal
lymphatics with blood and general edema by midgestation.
Lymphatic development continues largely unimpeded, but
severe vascular abnormalities also become apparent in the
intestine by E16.5. Mesenteric lymphatics are invading the
vascularized intestinal tube, and the mutants develop a gross
perturbation of what are normally separate, arborized vessels.
The mesenteric lymphatic vessels themselves appear structurally normal, but once these vessels reach the intestinal wall
they develop myriad connections with the blood circulation.
Real-time injection of fluorescent dextran into the circulation
reveals that the intestinal lymphatics become perfused with
dextran and are functionally indistinguishable from their
venous counterparts. The majority of these animals die
perinatally.14 Notably, some vascular beds in these animals
appear completely unaffected, including those found in the
lungs, where there is a high density of both lymphatic and
blood vessels.
Hematopoietic Requirement During
Lymphatic Development
The observation that SLP-76 knockout mice develop a
primary vascular defect was particularly surprising because
expression of this protein is confined to the hematopoietic
compartment, where it nucleates signaling complexes downstream of immunoreceptor activation. Expression of SLP-76
has not been detected in endothelial cells, even at the cardinal
vein during the emergence of LECs.14 Reconstitution of the
bone marrow and circulating blood cells in lethally irradiated
wild-type mice with Slp-76⫺/⫺ hematopoietic cells results in
the development of intestinal blood-lymphatic mixing, highlighting the requirement for SLP-76 in bone marrow– derived
cells.14 Furthermore, transgenic rescue of SLP-76 in a limited
profile of hematopoietic cells but not in endothelial cells is
sufficient for normal lymphatic development.16 Runx1⫺/⫺
mice, which fail to undergo definitive hematopoiesis, demonstrate similar blood-filled lymphatic sacs at E11.5, also
How does a hematopoietic signaling pathway regulate lymphatic vessel growth and development? A major insight into
this question came with the discovery that Podoplanin
(PDPN)-null mice exhibit blood-lymphatic mixing and vascular abnormalities that closely phenocopy those of mice
lacking SYK, SLP-76, and PLC␥2.18 –20 PDPN is a heavily
O-glycosylated type I transmembrane protein whose expression is largely restricted to glomerular podocytes, lung
alveolar type I cells, and LECs but is not seen in hematopoietic cells or blood endothelial cells. Endothelial loss of the
T-synthase enzyme required for PDPN synthesis is sufficient
for blood-lymphatic mixing like that observed in mice lacking the immune receptor signaling pathway in blood cells.19
Radiation chimeras confirm that the requirement for PDPN is
not in blood cells,18 consistent with an essential role in LECs.
These studies and the finding that loss of PDPN magnified
the penetrance of the vascular mixing phenotype in Vav-Cre;
Slp-76fl/fl animals placed PDPN in the same pathway as
SYK, SLP-76, and PLC␥2, but in a different cell type.
PDPN and SYK-SLP-76 Signaling Are Linked by
CLEC-2 receptors on Platelets
PDPN, also known as aggrus, was identified as a tumor cell
surface protein capable of initiating platelet aggregation.21,22
The mechanism for this response was recently identified as
PDPN-mediated activation of a novel platelet receptor,
C-type lectin-like receptor 2 (CLEC-2), that is highly expressed on platelets.23 The intracellular tail of CLEC-2
contains a single YxxL motif that initiates downstream
signaling through SYK and SLP-76 on ligand engagement of
a CLEC-2 dimer,24 providing a molecular explanation for
how PDPN and these hematopoietic signaling proteins may
be linked. Genetic deletion of CLEC-2 in mice reveals a
striking phenocopy of the blood-lymphatic mixing defects
seen in mice deficient for SLP-76 or PDPN.18,25 Radiation
chimeras reconstituted with Clec-2⫺/⫺ fetal liver cells develop the intestinal mixing phenotype, confirming a hematopoietic requirement for CLEC-2.18 In situ and flow cytometry
studies indicate that CLEC-2 is restricted to plateletgenerating megakaryocytes and platelets in the developing
embryo,18 although in older animals it is also reported to be
present on peripheral blood neutrophils.26 These studies
suggested that PDPN on LECs activates CLEC-2 receptors
and downstream SYK-SLP-76 signaling in platelets to initiate
and maintain blood-lymphatic vascular separation. This un-
2370
Arterioscler Thromb Vasc Biol
December 2010
Downloaded from http://atvb.ahajournals.org/ by guest on May 3, 2017
Figure. Platelets regulate bloodlymphatic vascular separation. A, Lymphatic vascular development begins at
the cardinal vein in the embryo, when
venous endothelial cells give rise to the
first LECs to form the lymph sacs. Platelet microthrombi are present on LECs at
the cardinal vein in wild-type embryos
but are absent in Clec-2⫺/⫺, Slp76⫺/⫺, and Pdpn⫺/⫺ embryos, which
develop blood-filled lymph sacs. These
primary misconnections lead to downstream blood-filled lymphatics. B, Abnormal blood-lymphatic vascular connections
form in the intestines of Clec-2⫺/⫺, Slp76⫺/⫺, and Pdpn⫺/⫺ mice. A proposed
mechanism of intestinal blood-lymphatic
mixing is shown, where vascular misconnections arise because of angiogenic invasion between blood and lymphatic vasculature. C, PDPN on the surface of
lymphatic endothelium binds to platelets
through the CLEC-2 receptor, leading to
SLP-76-dependent platelet activation.
Platelet activation mediates vascular separation through an unknown mechanism.
expected mechanism is confirmed by the finding that platelet-specific deletion of SLP-76 is sufficient to confer the
blood-lymphatic mixing phenotype.18 Importantly, separate
lines of investigation have provided genetic confirmation of
the role of platelets in this vascular regulatory mechanism.18,27 Platelet-null embryos generated either by deletion
of the transcription factor MEIS1 or through platelet-specific
expression of diphtheria toxin exhibit the blood-lymphatic
mixing phenotype.27 These studies demonstrate that platelets
are responsible for mediating blood and lymphatic separation
through activation of the CLEC-2 receptor by PDPN ligand
presented on the surface of LECs (Figure 1).
Future Directions
It remains unknown how abnormal blood-lymphatic vascular
connections arise in the absence of CLEC-2-PDPN signaling.
Platelet-LEC interactions can be seen in the cardinal vein
during the specification of PDPN-expressing LECs from
venous endothelial cells,18,20 but similar interactions have not
been detected in the intestine, where large numbers of
blood-lymphatic connections are formed.18 Because both
PDPN and CLEC-2 are transmembrane proteins, the mechanism requires direct contact between LECs and platelets. The
use of platelets as a means of sensing blood vessel contact by
LECs makes sense, as platelets are one of the few blood cell
types that cannot extravasate and enter lymphatic vessels,
even following trauma. Precisely how platelet activation by
LECs negatively regulates the formation of LEC connections
to blood vessels remains speculative. The requirements for
SYK and SLP-76 indicate a need for platelet activation
downstream of the PDPN-CLEC-2 interaction. The fact that
mice lacking platelet integrins required for platelet aggregation do not form blood-lymphatic connections suggests that
the formation of a platelet plug, the hallmark of plateletmediated hemostasis, may not be the key step downstream of
platelet activation. Instead, it is tempting to speculate that
platelet degranulation may release regulators of LEC growth
that inhibit the formation of blood-lymphatic connections.
Platelet ␣-granules are known to contain numerous angiogenic regulators, supporting the hypothesis that degranulation
is the mechanism by which platelet activation controls lymphatic growth. Additional genetic studies will be required to
test the effects of such agents on LEC growth and lymphatic
development.
The studies described above are also significant because
they describe a clear embryonic role for platelets that is not
connected to hemostasis. Platelet activation has been associated with many nonhemostatic roles in mature animals,
including inflammation,28,29 wound healing,30,31 primary tumor growth,32 and tumor metastasis,33 but few embryonic
roles have been defined. The lack of an embryonic phenotype
in NF-E2-deficient mice lacking most but not all platelets34,35
has suggested that platelets do not have such roles, but this is
clearly not the case, and it seems likely that future studies will
identify other roles for platelets in regulating development of
the cardiovascular and other systems.
Finally, it remains unclear whether PDPN or CLEC-2 play
roles outside lymphatic vascular development. The number of
CLEC-2 receptors on the surface of human or mouse platelets
has not yet been determined. However, comparison of hematopoietic and megakaryocyte gene analysis libraries, as well
as in situ hybridization studies of mouse megakaryocytes and
binding of anti-CLEC-2 antibodies and PDPN-Fc fusion
proteins, suggests that CLEC-2 may be one of the most highly
expressed activating receptors on the platelet surface.18,23 In
vitro studies of Clec-2⫺/⫺ platelets have suggested that
CLEC-2 deficiency does not affect collagen-induced aggregate formation.36 Furthermore, tyrosines in the YxxL motif of
platelet CLEC-2 receptors are not phosphorylated on flow
over collagen,36 suggesting that CLEC-2 is not involved in
platelet activation by classical hemostatic stimuli. The exis-
Bertozzi et al
tence of a PDPN-independent role for CLEC-2 remains
unclear and is an open question in the field. Future studies
addressing the hemostatic role(s) of CLEC-2 and PDPN are
likely to yield new insights into platelet biology.
Platelets: Regulators of Lymphatic Development
20.
Disclosures
None.
21.
References
Downloaded from http://atvb.ahajournals.org/ by guest on May 3, 2017
1. Drake CJ, Fleming PA. Vasculogenesis in the day 6.5 to 9.5 mouse
embryo. Blood. 2000;95:1671–1679.
2. de Bruijn MF, Speck NA, Peeters MC, Dzierzak E. Definitive hematopoietic stem cells first develop within the major arterial regions of the
mouse embryo. EMBO J. 2000;19:2465–2474.
3. Chen AT, Zon LI. Zebrafish blood stem cells. J Cell Biochem. 2009;108:
35– 42.
4. Stadtfeld M, Graf T. Assessing the role of hematopoietic plasticity for
endothelial and hepatocyte development by non-invasive lineage tracing.
Development. 2005;132:203–213.
5. Srinivasan RS, Dillard ME, Lagutin OV, Lin FJ, Tsai S, Tsai MJ,
Samokhvalov IM, Oliver G. Lineage tracing demonstrates the venous
origin of the mammalian lymphatic vasculature. Genes Dev. 2007;21:
2422–2432.
6. Saladin KS. Human Anatomy. New York, NY: McGraw-Hill Higher
Education; 2004.
7. Wigle JT, Harvey N, Detmar M, Lagutina I, Grosveld G, Gunn MD,
Jackson DG, Oliver G. An essential role for Prox1 in the induction of the
lymphatic endothelial cell phenotype. EMBO J. 2002;21:1505–1513.
8. Xu Y, Yuan L, Mak J, Pardanaud L, Caunt M, Kasman I, Larrivee B, Del
Toro R, Suchting S, Medvinsky A, Silva J, Yang J, Thomas JL, Koch
AW, Alitalo K, Eichmann A, Bagri A. Neuropilin-2 mediates VEGF-Cinduced lymphatic sprouting together with VEGFR3. J Cell Biol. 2010;
188:115–130.
9. Kim KE, Sung HK, Koh GY. Lymphatic development in mouse small
intestine. Dev Dyn. 2007;236:2020 –2025.
10. Alitalo K, Tammela T, Petrova TV. Lymphangiogenesis in development
and human disease. Nature. 2005;438:946 –953.
11. Oliver G. Lymphatic vasculature development. Nat Rev Immunol. 2004;
4:35– 45.
12. Cheng AM, Rowley B, Pao W, Hayday A, Bolen JB, Pawson T. Syk
tyrosine kinase required for mouse viability and B-cell development.
Nature. 1995;378:303–306.
13. Turner M, Mee PJ, Costello PS, Williams O, Price AA, Duddy LP,
Furlong MT, Geahlen RL, Tybulewicz VL. Perinatal lethality and
blocked B-cell development in mice lacking the tyrosine kinase Syk.
Nature. 1995;378:298 –302.
14. Abtahian F, Guerriero A, Sebzda E, Lu MM, Zhou R, Mocsai A, Myers
EE, Huang B, Jackson DG, Ferrari VA, Tybulewicz V, Lowell CA,
Lepore JJ, Koretzky GA, Kahn ML. Regulation of blood and lymphatic
vascular separation by signaling proteins SLP-76 and Syk. Science. 2003;
299:247–251.
15. Wang D, Feng J, Wen R, Marine JC, Sangster MY, Parganas E,
Hoffmeyer A, Jackson CW, Cleveland JL, Murray PJ, Ihle JN. Phospholipase C␥2 is essential in the functions of B cell and several Fc receptors.
Immunity. 2000;13:25–35.
16. Sebzda E, Hibbard C, Sweeney S, Abtahian F, Bezman N, Clemens G,
Maltzman JS, Cheng L, Liu F, Turner M, Tybulewicz V, Koretzky GA,
Kahn ML. Syk and Slp-76 mutant mice reveal a cell-autonomous hematopoietic cell contribution to vascular development. Dev Cell. 2006;11:
349 –361.
17. Samokhvalov IM, Samokhvalova NI, Nishikawa S. Cell tracing shows the
contribution of the yolk sac to adult haematopoiesis. Nature. 2007;446:
1056 –1061.
18. Bertozzi CC, Schmaier AA, Mericko P, Hess PR, Zou Z, Chen M, Chen
CY, Xu B, Lu MM, Zhou D, Sebzda E, Santore MT, Merianos DJ,
Stadtfeld M, Flake AW, Graf T, Skoda R, Maltzman JS, Koretzky GA,
Kahn ML. Platelets regulate lymphatic vascular development through
CLEC-2-SLP-76 signaling. Blood. 2010;116:661– 670.
19. Fu J, Gerhardt H, McDaniel JM, Xia B, Liu X, Ivanciu L, Ny A, Hermans
K, Silasi-Mansat R, McGee S, Nye E, Ju T, Ramirez MI, Carmeliet P,
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
2371
Cummings RD, Lupu F, Xia L. Endothelial cell O-glycan deficiency
causes blood/lymphatic misconnections and consequent fatty liver disease
in mice. J Clin Invest. 2008;118:3725–3737.
Uhrin P, Zaujec J, Breuss JM, Olcaydu D, Chrenek P, Stockinger H,
Fuertbauer E, Moser M, Haiko P, Fassler R, Alitalo K, Binder BR,
Kerjaschki D. Novel function for blood platelets and podoplanin in
developmental separation of blood and lymphatic circulation. Blood.
2010;115:3997– 4005.
Kato Y, Fujita N, Kunita A, Sato S, Kaneko M, Osawa M, Tsuruo T.
Molecular identification of Aggrus/T1␣ as a platelet aggregationinducing factor expressed in colorectal tumors. J Biol Chem. 2003;278:
51599 –51605.
Kaneko M, Kato Y, Kunita A, Fujita N, Tsuruo T, Osawa M. Functional
sialylated O-glycan to platelet aggregation on Aggrus (T1␣/Podoplanin)
molecules expressed in Chinese hamster ovary cells. J Biol Chem. 2004;
279:38838 –38843.
Suzuki-Inoue K, Fuller GL, Garcia A, Eble JA, Pohlmann S, Inoue O,
Gartner TK, Hughan SC, Pearce AC, Laing GD, Theakston RD, Schweighoffer E, Zitzmann N, Morita T, Tybulewicz VL, Ozaki Y, Watson SP. A
novel Syk-dependent mechanism of platelet activation by the C-type
lectin receptor CLEC-2. Blood. 2006;107:542–549.
Suzuki-Inoue K, Kato Y, Inoue O, Kaneko MK, Mishima K, Yatomi Y,
Yamazaki Y, Narimatsu H, Ozaki Y. Involvement of the snake toxin
receptor CLEC-2, in podoplanin-mediated platelet activation, by cancer
cells. J Biol Chem. 2007;282:25993–26001.
Suzuki-Inoue K, Inoue O, Ding G, Nishimura S, Hokamura K, Eto K,
Kashiwagi H, Tomiyama Y, Yatomi Y, Umemura K, Shin Y, Hirashima
M, Ozaki Y. Essential in vivo roles of the C-type lectin receptor CLEC-2:
embryonic/neonatal lethality of CLEC-2-deficient mice by blood/
lymphatic misconnections and impaired thrombus formation of CLEC-2deficient platelets. J Biol Chem. 2010;285:24494 –24507.
Kerrigan AM, Dennehy KM, Mourao-Sa D, Faro-Trindade I, Willment
JA, Taylor PR, Eble JA, Reis e Sousa C, Brown GD. CLEC-2 is a
phagocytic activation receptor expressed on murine peripheral blood
neutrophils. J Immunol. 2009;182:4150 – 4157.
Carramolino L, Fuentes J, Garcia-Andres C, Azcoitia V, Riethmacher D,
Torres M. Platelets play an essential role in separating the blood and
lymphatic vasculatures during embryonic angiogenesis. Circ Res. 2010;
106:1197–1201.
Clark SR, Ma AC, Tavener SA, McDonald B, Goodarzi Z, Kelly MM,
Patel KD, Chakrabarti S, McAvoy E, Sinclair GD, Keys EM, AllenVercoe E, Devinney R, Doig CJ, Green FH, Kubes P. Platelet TLR4
activates neutrophil extracellular traps to ensnare bacteria in septic blood.
Nat Med. 2007;13:463– 469.
Gawaz M, Neumann FJ, Dickfeld T, Koch W, Laugwitz KL, Adelsberger H,
Langenbrink K, Page S, Neumeier D, Schomig A, Brand K. Activated
platelets induce monocyte chemotactic protein-1 secretion and surface
expression of intercellular adhesion molecule-1 on endothelial cells. Circulation.
1998;98:1164–1171.
Lesurtel M, Graf R, Aleil B, Walther DJ, Tian Y, Jochum W, Gachet C,
Bader M, Clavien PA. Platelet-derived serotonin mediates liver regeneration. Science. 2006;312:104 –107.
de Boer HC, Verseyden C, Ulfman LH, Zwaginga JJ, Bot I, Biessen EA,
Rabelink TJ, van Zonneveld AJ. Fibrin and activated platelets cooperatively guide stem cells to a vascular injury and promote differentiation
towards an endothelial cell phenotype. Arterioscler Thromb Vasc Biol.
2006;26:1653–1659.
Ho-Tin-Noe B, Goerge T, Cifuni SM, Duerschmied D, Wagner DD.
Platelet granule secretion continuously prevents intratumor hemorrhage.
Cancer Res. 2008;68:6851– 6858.
Nieswandt B, Hafner M, Echtenacher B, Mannel DN. Lysis of tumor cells
by natural killer cells in mice is impeded by platelets. Cancer Res.
1999;59:1295–1300.
Shivdasani RA, Rosenblatt MF, Zucker-Franklin D, Jackson CW, Hunt P,
Saris CJ, Orkin SH. Transcription factor NF-E2 is required for platelet
formation independent of the actions of thrombopoietin/MGDF in
megakaryocyte development. Cell. 1995;81:695–704.
Levin J, Peng JP, Baker GR, Villeval JL, Lecine P, Burstein SA, Shivdasani RA. Pathophysiology of thrombocytopenia and anemia in mice
lacking transcription factor NF-E2. Blood. 1999;94:3037–3047.
Hughes CE, Navarro-Nunez L, Finney BA, Mourao-Sa D, Pollitt AY,
Watson SP. CLEC-2 is not required for platelet aggregation at arteriolar
shear. J Thromb Haemost. 2010.
Downloaded from http://atvb.ahajournals.org/ by guest on May 3, 2017
Platelets: Covert Regulators of Lymphatic Development
Cara C. Bertozzi, Paul R. Hess and Mark L. Kahn
Arterioscler Thromb Vasc Biol. 2010;30:2368-2371; originally published online November 11,
2010;
doi: 10.1161/ATVBAHA.110.217281
Arteriosclerosis, Thrombosis, and Vascular Biology is published by the American Heart Association, 7272
Greenville Avenue, Dallas, TX 75231
Copyright © 2010 American Heart Association, Inc. All rights reserved.
Print ISSN: 1079-5642. Online ISSN: 1524-4636
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
http://atvb.ahajournals.org/content/30/12/2368
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published
in Arteriosclerosis, Thrombosis, and Vascular Biology can be obtained via RightsLink, a service of the
Copyright Clearance Center, not the Editorial Office. Once the online version of the published article for
which permission is being requested is located, click Request Permissions in the middle column of the Web
page under Services. Further information about this process is available in the Permissions and Rights
Question and Answer document.
Reprints: Information about reprints can be found online at:
http://www.lww.com/reprints
Subscriptions: Information about subscribing to Arteriosclerosis, Thrombosis, and Vascular Biology is online
at:
http://atvb.ahajournals.org//subscriptions/