Bypass research not in vein

Repeat bypass operations might soon be a thing of the past, thanks to new research by a team at St George`s Hospital Medical School in Tooting, London. The origins of diseased cells in vein grafts that form following heart bypass operations have been found for the first time using a new model. The discovery by Professor Xu and colleagues is published today in the journal, Circulation Research.

Every week around 15 people have heart bypass operations in St George`s Hospital alone. In each case, a piece of the long vein from the patient`s leg is cut away, and used to link two pieces of healthy artery or vein in the heart, replacing a diseased section. This is a very successful operation but over time, this new piece of vessel may itself become diseased and give the patient a high risk of heart attack. At present, the only way to stop this happening is to perform another bypass operation. But, as with all major operations, the older the patient, the greater the risk.

Now researchers have the chance to solve this problem once and for all. Professor Xu and colleagues know that diseased vessel grafts that lead to heart attack are caused by a build up of cells known as smooth muscle cells in the inner layer of the vessel wall. The more they build up, the more the vessel is diseased. But until now, researchers were unsure about where these smooth muscle cells come from. Do they come from the original piece of vein, the newly grafted piece or even bone marrow stem cells? By labelling the donor and recipient smooth muscle cells with a marker gene, as well as carrying out experiments on bone marrow, the team found that the diseased cells come from both the original vessel and the newly grafted part, with a larger proportion – 60 percent coming from the donor part. No smooth muscle cells were found to come from bone marrow stem cells.

Knowing that 60 percent of the smooth muscle cells come from the donor piece of vein means it will be possible to develop treatment to make the new piece of vein resist disease. This treatment can be done once the healthy vein has been removed from the leg, but before it is reinserted into the patient – making it a non-invasive treatment.

“We now know where the cells in the lesions come from, which is a big breakthrough,” said Professor Xu. “In the next two years we will work out the best way of treating the vein graft outside of the body, and we hope to start clinical trials in about 5 years”, he added.