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Hello my name is Bill Aird from Harvard Medical School and I'm
going to be talking about Evolutionary Considerations and the Endothelium.
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The endothelium, which forms the inner cell lining of lymphatic and blood vessels,
is a spatially distributed organ system extending to all recesses of the human body.
In an average-sized human being,
the endothelium weighs one kilogram,
covers a total surface area of between 4,000 and 7,000 square meters,
and spans over 100,000 miles of blood vessels,
the vast majority of which are invisible to the human eye.
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The endothelium is not an inert layer of
nucleated cellophane as it was originally portrayed,
but rather is a highly metabolically active organ that participates in
many physiological functions including the control of barrier function,
leukocyte trafficking, the maintenance of blood fluidity in vasomotor tone,
innate and acquired immunity,
as well as proliferation and angiogenesis.
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A third point to make is that the endothelium is
involved in every human disease either as
a primary determinant of pathophysiology or as a victim of collateral damage.
As a final introductory comment,
endothelial cell phenotypes are differentially regulated in
both structure and function across space and time giving
rise to the phenomenon that we term in the vascular biology community,
endothelial cell heterogeneity.
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The goal of this presentation is to underscore the importance
of endothelial cell heterogeneity as a unifying feature of
this cell layer and indeed to argue that phenotypic heterogeneity
is an evolutionarily conserved core property of the cell type,
one that has important diagnostic and therapeutic considerations.
I will begin with a broad overview of the history of the field with
