In the first study of its kind looking
at the safety of stem cells in animals closely related to humans, scientists
worked on rhesus macaques. Previous studies have focused on mice, and one of
the main problems is that when stem cells are implanted, tumours are very
likely to form. Reassuringly, this does not seem to be the case in monkeys.
In the study,
published in Cell Reports, the researchers took cells from a monkey's skin and
reprogrammed them into a stem-cell-like state, making induced pluripotent stem cells, or iPSCs. They then coaxed these iPSCs into becoming bone-forming cells,
before implanting them into the same animal the cells were taken from.
It took 20 times as many cells to form
tumours in the monkeys compared to what was previously seen in mice. Lead
researcher Dr Cynthia Dunbar, of the National Heart, Lung, and Blood
Institute in the USA said 'tumour formation is very slow and requires large
numbers of iPSCs', a result that bodes well for the therapeutic use of stem
cells in humans.
iPSCs, which are made from a patient's
own cells, can theoretically be transformed into any other kind of cell. As
such, developing their use in the clinic could lead to a range of treatments,
for instance for conditions such as heart disease, diabetes or Parkinson's disease.
Martin Pera, professor of stem cell sciences
at the University of Melbourne, told
Discovery News that this work is 'another step
towards the development of safe stem cell therapies for human disease'.
Speaking to Nature News, Dr Ashleigh Boyd, a stem cell researcher at University College London who was
not involved in the work, said: 'It's important because the field is very
controversial right now'. Because of the contentious nature and high clinical
potential of the research, more work needs to be done to validate the results. Indeed,
Professor Pera told
Discovery News that 'the study is small, it relates
to the safety of only one type of specialised cell, and does not show directly
that the bone grafts would heal or repair fractures'.
Dr Dunbar now hopes to repeat the work
using heart, liver and white blood cells. She said: 'We hope the robust model
established in this paper can be used to improve the chance that first-in-human
iPSC-derived therapies will be safe and effective'.