ENDOTHELIAL CELL CYTOSKELETON REORGANIZATION DURING FUNCTIONAL MONOLAYER FORMATION IN VITRO
A.S. Shakhov,1 À.D. Verin,2 I.B. Alieva 1,2,*
1 Electron Microscopy Department, A. N. Belozersky Institute of Physical and Chemical Biology,
Moscow State University, Moscow, Russia, and 2 Vascular Biology Center, Georgia Regents University,
Augusta, GA 30912, USA;
*e-mail: irina_alieva@belozersky.msu.ru
The endothelium lining the inner surface of blood vessels regulates vascular permeability, permitting the
exchange between the blood circulating in vessels and tissue fluid, and performs thereby the barrier function.
Endothelial cells cultured in vitro retain the ability to perform a barrier function that is inherent in vascular endothelial
cells in vivo. Endothelial monolayer in vitro is a unique model system that allows studying the interaction
of cytoskeletal and adhesive structures of endothelial cells from the earliest stages of its formation. In this
paper we describe and characterize quantitatively the changes in the cytoskeleton of endothelial cells from the
time of endothelial cells spreading on the glass and formation of the first contacts between neighboring cells until
the formation of a functional confluent monolayer. The main type of intermediate filaments of endothelial
cells were vimentin filaments. The location of vimentin filaments and their number did not change at different
stages of the endothelial monolayer formation, they occupied more than 80 % of the cells. The system of actin
filaments in endothelial cells was represented by the cortical actin at the cell periphery and bundles of actin
stress fibers arranged in parallel. Upon the formation of contacts with neighboring cells the number and thickness
of actin filaments increased. In addition, the formation of the endothelial monolayer led to changes in microtubule
network, which was evident from the increase in the number of microtubules at the cell edge. Further,
at all stages of assembling the endothelial monolayer, the number of microtubules formed at the cell margin in
the area of cell-cell contacts exceeded the number of microtubules in the area of the free lamellae.
Key words: pulmonary endothelium, endothelial monolayer formation, endothelial cell cytoskeleton, intermediate
filaments, actin filaments, microtubules
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