An unlikely brew of seaweed and glow-in-the-dark biochemical agents may hold the key to the safe use of transplanted stem cells to treat patients with severe peripheral arterial disease, according to a team of veterinarians, basic scientists and interventional radiologists at Johns Hopkins University, USA.
In a preliminary “proof of concept” study in rabbits, Johns Hopkins scientists safely and successfully delivered therapeutic stem cells via intramuscular injections and then monitored the stem cells’ viability once they reached their targets.
A report of the study by Johns Hopkins radiologists was presented at the Society of Interventional Radiology’s 34th annual scientific meeting yesterday.
Stem cells hold promise in treating peripheral arterial disease by reconstituting or increasing the number of blood vessels to replace or augment those choked off by plaque build-up.
Many cases of peripheral arterial disease can be treated with angioplasty or stents, similar to approaches used in coronary artery disease. But for some patients with extensive disease, conventional treatment is not feasible, researchers say.
Among the technical hurdles to improving blood flow in such patients, according to Dara L. Kraitchman, associate professor of radiology at Johns Hopkins, is a means of telling doctors whether injected stem cells are staying alive and reaching the right targets to grow and develop into the needed new tissue.
To overcome rejection of the stem cells by the body’s immune system, researchers first created a novel “capsule” derived from seaweed, which was used to surround and protect the cells from attack by the host’s immune system.
Within the seaweed capsule, they added X-ray contrast agents to allow the capsules to be seen on X-ray angiography.
Next, they engineered the stem cells within the capsules to produce luciferase, the same bioluminescent chemical produced by fireflies, which is highly visible under bioluminescence imaging.
“Once we were able to trick the immune system into not attacking the cells, we had to know they arrived at their destination and were living,” says Kraitchman.
“We could use standard X-ray angiography of blood vessels to see the transplanted cells. When they lit up like fireflies at night, we knew they were still alive.”