A new study by scientists at the Helmholtz Association of German Research Centers reveals that blood vessels "sprout" under pressure, pointing to blood pressure as the factor that pushes for the opening of small capillaries during angiogenesis, the development of new blood vessels.
The team revealed that blood exerts pressure that pushes the membrane of endothelial cells to cave in and grow into the cell's body, ultimately leading to the formation of a continuous vessel. This process is guided by the cell itself in conjunction with the actomyosin filaments of its cytoskeleton.
Scientists now have a detailed view of how blood capillaries form, knowledge that can help to better understand important biological processes such as embryonic development, cancer and diabetes.
"During 'sprouting angiogenesis,' new cells grow from the wall of existing nearby capillaries to make a new capillary loop. But until now, scientists did not know how the lumen forms," Holger Gerhardt, who led the team, said in a press release.
Gerhardt and his team used a spinning-disk confocal microscope in order to gain a high spatial and temporal resolution look at zebrafish embryos, analyzing endothelial cells that had been genetically labeled with a fluorescing protein to make them easily visible. During the study, they viewed the process of blood squeezing into the endothelial cells and, during this time, the growth of the new lumen membrane.
Analysis revealed that cell activity controls the progression of this infolding process by pushing back smaller side branches and small bubbles using actin fibers that are built and then subsequently used by contracting them using myosin filaments, allowing the new capillary lumen to grow at the tip.
Angiogenesis is important during embryonic development and wound healing as well as during the process of cancer growth, and these new findings could help better our understanding of these facets of biology.
"Blood vessels in tumors are not normal. They are leaky and often unable to control their diameter," said Véronique Gebala, lead author of the study. "The property of the lumen may also be relevant to other diseases," Gerhardt added.
"The next logical step is to study pathological situations," Gebala concluded.
The findings were published in the Feb. 29 issue of Nature Cell Biology.
