Smooth-muscle cells show green in this comparison of blood vessels grown with (right) and without (left) growth factor FGF9. Without muscle, vessels don't pump.
What’s the News: Biologists may have been barking up the wrong tree when it comes to growing new blood vessels to provide blood to tissues damaged by heart disease. The vessels that form under the influence of a growth factor intended to kick-start the process are sickly and shrivel up within a year, but a new study
in Nature Biotechnology ($) shows that focusing on making the surrounding cells provide support may solve the problem. What’s the Context:
Patients who suffer from heart disease don’t have enough blood flowing to the heart and the brain, respectively. Scientists have been seeking treatments---such as the injection of a growth factor called FGF2---that encourage a patient’s own blood vessels to grow and restore blood flow in damaged tissues, but with limited success.
Blood vessels are thin tubes of endothelial cells. They are wrapped in smooth muscle cells, which contract to push blood along. The team hypothesized that blood vessels grown with FGF2 had failed because FGF2 only encourages the growth of endothelial cells, not smooth muscle cells, and thus the vessels couldn’t pump.
How the Heck:
The team identified a growth factor called FGF9 that causes smooth muscle cells to grow around blood vessels and, after studying it in cell culture, injected it into the hind legs of elderly mice whose femoral arteries had been sewn closed, cutting off the blood flow.
Mice that received FGF9 and control mice grew a similar number of new blood vessels, but mice with FGF9 had far more smooth muscle cells around the vessels and more blood flow. These mice also got back on their feet faster, using their injured limbs ten times more than mice who hadn’t received FGF9.
The team also found that vessels grown in a dish in the presence of both FGF2 and FGF9 were thriving after a year, while vessels grown only with FGF2 choked and died.
The Future Holds: Further experiments to see how FGF9 can work together with FGF2 in potential treatments for heart disease. The researchers also point out that FGF9 might be useful for encasing transplanted blood vessels
in smooth muscle cells, thus boosting their rates of success as well. Reference: Matthew J Frontini, Zengxuan Nong, Robert Gros, Maria Drangova, Caroline O'Neil, Mona N Rahman, Oula Akawi, Hao Yin, Christopher G Ellis, J Geoffrey Pickering. Fibroblast growth factor 9 delivery during angiogenesis produces durable, vasoresponsive microvessels wrapped by smooth muscle cells. Nature Biotechnology, 2011; doi:10.1038/nbt.1845