Antibody cocktail promises safer stem cell therapy

Fears that stem cell therapies could seed a bizarre form of tumour may be calmed by a cocktail of antibodies. Because human embryonic stem cells (ESCs) can develop into any type of cell, they hold great promise in the field of regenerative medicine, which aims to replace cells or tissues lost to injury or disease. But their broad developmental capacity could also be their undoing: if any undifferentiated cells remain in a culture of, say, <a href="www.bestnikeshoesforstore.com"><strong>nike shoes online</strong></a> neurons grown from ESCs, they could run riot after being transplanted into a patient. The concern is that they might form tumours known as "teratomas", strange mixtures of tissues that can even include teeth and hair. The same fears surround induced pluripotent stem cells (iPSCs) – genetically reprogrammed cells that mimic the properties of ESCs. To find a way of purging unwanted ESCs from cultures growing into other cell types, researchers led by Chad Tang and Micha Drukker – working in the lab of Irving Weissman at Stanford University, California – screened a library of antibodies against human ESCs to find those that bound most strongly to the cells. One antibody, which turned out to recognise a previously unknown carbohydrate dubbed SSEA-5, came out "at <a href="www.bestnikeshoesforstore.com"><strong>cheap nike shoes </strong></a> the top of the heap", says Weissman. Next the researchers turned to a method called fluorescence-activated cell sorting (FACS), which can separate cells depending on whether they carry an antibody tagged with a fluorescent label. They stuck such a fluorescent label to their new antibody, before adding it to human ESCs that were developing into blood cells. Then they used FACS to pick out cells the antibody bound to. Finally, they injected the remaining cells into mice to see if they formed teratomas. By itself, the new antibody did not completely purge the offending cells. But when it was combined with two other antibodies that also target molecules found on ESCs, no teratomas formed. "This is a proof of concept," says Tang, who notes that different combinations of antibodies may be required for cultures developing into different types of cells. Two companies – Geron, based in Menlo Park, California, and Advanced Cell <a href="www.bestnikeshoesforstore.com"><strong>nike heels for women</strong></a> Technology (ACT) – are now running clinical trials of cells grown from human ESCs to treat spinal injuries and some forms of blindness respectively. Both had to provide extensive evidence from animal experiments to convince the US Food and Drug Administration that the transplanted cells will not form teratomas. Robert Lanza, who heads ACT's research labs in Marlborough, Massachusetts, warns that the new technique will not eliminate the need for animal safety studies. But he says that it may be useful in purifying certain cell types that can be cultured only for short periods, and so will be found only in cultures that may still contain many ESCs. "It could be the crucial step that allows partially differentiated cultures to be used <a href="http://www.xinzhouba.com/view.php?id=28115"><strong>hogan2011</strong></a> clinically," he says. Journal reference: Nature Biotechnology, DOI: 10.1038/nbt.1947 If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.