Working Group on Vascular Biology
July 13th, 2003
08:00 to 12:00
Hall 10
The International Convention Center, Birmingham
Chair: Peter J. Newman (USA)
Co-chairs: Michael C. Berndt (Australia), John Griffin (USA),
Irène Juhan-Vague (France), Klaus T. Preissner (Germany)
The SSC Workshop in Vascular Biology met for the first time on Sunday, July
13th, 2003, in Birmingham, England. Though there were a rich
variety of topics relevant to the field of vascular biology that might have
been addressed, and may be addressed at future workshops, the Organizing
Committee chose two topics that they felt would be timely and relevant to
the mission of the SSC and of the ISTH: (1) Detection, measurement, function,
and clinical significance of membrane microparticles derived from blood and
vascular cells, and (2) Real-time measurements of blood cell interactions
with the vessel wall – applications of intravital microscopy and other flow
systems. Six internationally-recognized experts, three in each of these
two fields, were invited to speak. The audience was estimated at 200-300,
with standing room only at some points during the morning.
SESSION I – Detection, measurement, function, and
clinical significance of membrane
microparticles derived from blood and vascular cells
Alan D. Michelson (Center for Platelet Function Studies, University
of Massachusetts Medical School, USA) spoke on "Detection, standardization,
and clinical correlates of platelet-derived microparticles". Dr.
Michelson provided a brief historical overview of the field of platelet-derived
microparticles, and went on to describe how they are formed, the cells from
which they are derived, and some of the functions that have been attributed
to them. Their clinical relevance, as well as human disorders associated
with the generation of circulating microparticles was also discussed.
Jean Marie Freyssinet (Institut d'Hématologie et d'Immunologie
Faculté de Médecine - Université Louis Pasteur, Strasbourg,
France) spoke on "Detection of cellular membrane microparticles in the
vascular compartment". Dr. Freyssinet brought forward a variety
of timely issues that could be discussed in greater detail in future meetings,
including how microparticles are quantitated, appropriate markers that could
be used to identify their cellular sources, and the development of standards
by which microparticles should be prepared and defined. Clinical studies
and new applications were also discussed.
Bernd Engelmann (Institute for Clinical Chemistry - Ludwigs-Maximilians
University, Munich, Germany) spoke on "The role of microparticles in the
initiation of blood coagulation". Dr. Engelmann focused on tissue-factor-containing
microparticles and their potential to promote blood clotting – a topic that
received much discussion both here and during the ISTH meeting proper.
A number of unresolved issues were addressed and discussed, including identification
of the source of tissue factor, and its biologic activity in microparticles.
This session ended with a brief panel discussion of topics that could be
discussed in future vascular biology workshop meetings. There was good
consensus that the issue of blood cell-derived microparticles had much more
to offer in future meetings of the SSC.
SESSION II – Real-time measurements of blood cell
interactions with the vessel wall –
applications of intravital microscopy and other flow systems
Barry Coller (Rockefeller University, New York, USA, with co-authors
Marketa Jirouskova, Heikki Vaananen, and Jay Degen) spoke on "Real-Time
Imaging of Carotid Artery Thrombosis in the Mouse: Studies on the Role of
Fibrinogen and the Fibrinogen Gamma Chain". Dr. Coller brought
forward a number of important issues related to the standardization of models
currently in use to examine thrombosis and hemostasis in real time, including
the types of anesthetics used, how blood vessels should be damaged, the positive
and negative attributes of using different vascular beds for analysis, and
how to best capture and quantify the images obtained.
Steffen Massberg (German Heart Center - Technical University, Munich,
Germany) spoke on "Platelet-vessel wall interactions in vivo -implications
for thrombosis and atherosclerosis". There is a growing awareness
of potential relationships between inflammation, thrombosis, and the development
of atherosclerotic lesions, and Dr. Massberg has been a the forefront of
this field. He provided a stimulating discussion of the role of platelet
interactions with the vessel wall in athero-progression and in arterial thrombosis.
The role of leukocytes with and without bound platelets, and the role of
platelet monolayers in leukocyte recruitment was also discussed.
Jerry Ware (Scripps Research Institute, USA) spoke on "Relative contributions
of GPVI and the GPIb complex to platelet adhesion, activation, and thrombus
formation under flow - different models/different insights". Dr.
Ware described the strengths and weaknesses of the most commonly-used methods
for determining platelet function in vitro and in vivo, including the use
of tail bleeding times, standard aggregometry, flow chamber studies, and
the ferric chloride model of carotid artery denudation. The impact
of variability in the reagents (e.g. types of collagens) used, the impact
of shear, and the size of mouse versus human platelets was discussed.
Recently developed GPVI-null mice were used as an example of how subjecting
animals/platelets to different models can lead to different insights into
vascular physiology and blood cell function.
The session ended with much discussion from the audience, an offer by several
members of the audience to participate more actively in the development of
next year’s program, and a suggestion that the organizing committee entertain
the notion of including additional topics in vascular biology (i.e. angiogenesis)
in future workshops.