Scientists must develop new ways of harvesting and identifying a type of stem cell before they use them in clinical trials, according to research published today in the journal Blood.

The research was led by Senior Research Fellow Dr Manuel Mayr and his team at the British Heart Foundation Centre of Research Excellence at King’s College London. From blood samples collected from human volunteers, the King’s team isolated mononuclear cells, in order to grow endothelial progenitor cells. These can develop into endothelial cells, which form the lining of our blood vessels.

EPCs are a type of stem cell that originate in the bone marrow and circulate in the blood. They have been suggested as a source of stem cell-based therapies to contribute to the repair of heart tissue.

The scientists used a technique called proteomics to examine the characteristics of these cells.

Dr Mayr explains: “Surprisingly, we found that conventional isolation methods used by scientists and doctors do not result in a pure cell sample because they are also contaminated with markers from another type of blood cell called platelets.” So the markers scientists use to identify EPCs were also present in the platelets. Some of the cells used in clinical trials seemed like EPCs, but were a different type of cell.

Professor Peter Weissberg, Medical Director at the BHF, said: “This research demonstrates the value of carrying out fundamental cell biology research to fully understand the sources of stem cells before they proceed into clinical trials, so we understand exactly which cells are able to contribute to any repair to the heart and whether they are safe.”