Researchers are working on many different approaches to spur regrowth of blood vessels in the body. Here is one of them: "researchers have demonstrated a new and more effective method for regrowing blood vessels in the heart and limbs ... The treatment method [could] allow doctors to bypass surgery and instead repair damaged blood vessels simply by injecting a lipid-incased substance into a patient. Once inside the body, the substance stimulates cell growth and spurs the growth of new blood vessels from pre-existing ones. ... Others have tried using growth factors to stimulate vessel growth in clinical trials and have not been successful. We think that a major reason for this is that previous methods assumed that the diseased tissues retained the ability to respond to a growth stimulus. Our method basically delivers extra components that can restore growth factor responsiveness to the tissue of patients with long-standing clinical disease. ... The method combines a growth factor - a substance capable of stimulating cellular growth, proliferation and cellular differentiation, as well as healing wounds - known as fibroblast growth factor 2 (FGF-2) with a lipid-embedded receptor to enhance its activity. A challenge for scientists and engineers, however, has been getting FGF-2 to bind with cell receptors - the very molecules often found on the surface of the cell that receive chemical signals and direct activity in the cell from outside sources. To overcome this, [the new] method embeds the growth factors in synthetic lipid-based nanoparticles containing a coreceptor known as syndecan-4. The nanoparticles containing co-receptors that, when delivered with the growth factor, enable improved cell binding so that the growth factor can direct the targeted cell to divide, proliferate and form new cells for tissue regrowth. The incased substance was injected into rats with hindlimb ischemia and stimulated a complete recovery from the ischemia in just seven days."