Safety fears over ES cells allayed

Human embryonic stem cells (ES cells) do not show signs of genetic instability when grown for extended periods in the laboratory, UK researchers say. The results, published in the journal Nature Genetics, are 'not only surprising but good news for potential therapeutic use', says study leader Roger Pederson. The scientists, based at the University of Cambridge, have shown that the process of 'genetic imprinting' - the 'tagging' of certain genes, which marks them as either maternal or paternal in origin - does not appear to be disrupted in ES cells grown in culture.

For most genes in the developing mammalian embryo, both the maternal and paternal copies are either switched on or off in a particular tissue at any given point. But for a small number of 'imprinted' genes, only the copy from one parent is switched on, whilst the other remains inactive - a process crucial to normal development. Previous research carried out on mouse ES cells has detected changes in genetic imprinting, when the cells are grown in the laboratory, and scientists feared that the same might be true of human ES cells. However, the latest study suggests this is not the case, paving the way for new therapies based on these cells.

The scientists studied six of the 75 genes known to be imprinted in humans, in four different ES cell lines, and found that all had remained stable. 'The remarkable consistency we found between four lines and with respect to six genes suggests the stability is a property of human ES Cells, not just a property of these lines or genes', said Pederson. Had the cells not appeared to be so stable, then far more work would have been necessary to ensure their safety, he added. UK developmental biologist Robin Lovell-Badge agreed that it was 'very important' for the human stem cell field to have this stability demonstrated. However, more work into the safety of ES cells still needs to be done, say experts.

Many researchers hope that research into ES cells, the body's 'master cells' that can grow into almost any type of body cell, will yield new treatments for a range of disorders. 'As an advocate myself of the therapeutic use of these cells, I couldn't sleep at night if I hadn't done this study', said Pederson. The stem cell scientist, who moved from the US to the UK to carry out his research, said the intellectual climate for researchers working in this field in Britain was 'unequalled', but that more investment was urgently needed to take the work forward.