d vasculature as well as the newly formed vascular mimicry conduits, the researchers found that macrophages quickly migrate to oxygen-deprived environments and form these vessel-like channels. Experiments spearheaded by Barnett and Rosenfeld showed that these tubular structures are lined with cells that express macrophage cell surface markers.
"Macrophages are capable of forming a three-dimensional network," said Rosenfeld.
These vessel-like channels appeared too small to carry red blood cells, but the researchers believe that the low oxygen concentrations within tumors drive macrophages to form this network of channels to transport dissolved oxygen and glucose.
A Possible Cancer Target
The findings could explain why current drugs to slow angiogenesis do not slow tumor growth in some patients. Friedlander said future cancer therapies could starve tumors by combining current vessel-targeting drugs with drugs to influence macrophage activity.
"There may be an opportunity to intervene therapeutically," Friedlander said.
In addition to providing a new approach to cancer, Friedlander added that future studies could focus on better understanding how macrophages influence retinal angiogenesis and blood flow in the eye--a key concern for people with diseases like age-related wet macular degeneration, where leaky vessels can cause vision loss.
The researchers added that this study would not have been possible without TSRI's core facilities scientists, who aided with electron microscopy, confocal imaging, in vivo mouse efforts and quantitative analysis.
In addition to Friedlander, Barnett and Rosenfeld, authors of the study, "Macrophages form functional vascular mimicry channels in vivo," were Malcolm Wood, William Kiosses, Yoshihiko Usui, Valentina Marchetti and Edith Aguilar, all of TSRI at the time of the study.
The study was supported by the National Institutes of Health (grant R01EY011254).
About The Scripps Research Institute
The Scripps Research Institute (TSRI) is one of the world's largest independent, not-for-profit organizations focusing on research in the biomedical sciences. TSRI is internationally recognized for its contributions to science and health, including its role in laying the foundation for new treatments for cancer, rheumatoid arthritis, hemophilia, and other diseases. An institution that evolved from the Scripps Metabolic Clinic founded by philanthropist Ellen Browning Scripps in 1924, the institute now employs more than 2,500 people on its campuses in La Jolla, CA, and Jupiter, FL, where its renowned scientists--including two Nobel laureates and 20 members of the National Academy of Science, Engineering or Medicine--work toward their next discoveries. The institute's graduate program, which awards PhD degrees in biology and chemistry, ranks among the top ten of its kind in the nation. For more information, see http://www.