Stem cells may be present in breast milk and could be used therapeutically. The intense ethical debate surrounding the use of embryonic stem cells could therefore be bypassed if claims made by a team of scientists in Australia are confirmed.
The researchers at the University of Western Australia first discovered stem cells in human breast milk in 2008, a finding that generated some controversy in the field of stem cell research.
One of the lead scientists in the team, Dr Foteini Hassiotou, will be presenting the group's work at a conference in Vienna in early 2012. The presentation will apparently include evidence that the stem cells can be coaxed into forming all three embryonic germ layers (endoderm, mesoderm and ectoderm) — a prerequisite for truly embryonic stem cells.
Dr Hassiotou said: 'They can become bone cells, joint cells, fat cells, pancreatic cells that produce their own insulin, liver cells that produce albumin and also neuronal cells'.
Being able to derive all of these different cell types from stem cells obtained from milk is a very attractive prospect, as it would effectively nullify the need to isolate cells from early-stage embryos and sidestep the attendant ethical issues.
Other adult stem cells do exist — for example hematopoietic stem cells that generate blood cells — but these cells cannot generate as many different cell types as embryonic stem cells. Dr Hassiotou says that the newly discovered embryonic stem cells can be obtained in large quantities in breast milk, and constitute up to two percent of the total cells present.
However, many experts in the field have already voiced their reservations regarding such claims. Professor Robin Lovell-Badge, a group leader in stem cell biology and developmental genetics at the National Institute for Medical Research, UK, told New Scientist: 'Perhaps there are some mammary gland stem cells that can be coaxed to have a slightly broader potential than normal, but I very much doubt that embryonic-like cells normally exist in the breast. For one thing, you would expect tumours to be more common than they are'.
Dr Hassiotou aims to silence the critics by testing whether or not these cells form tumours containing tissue from all three embryonic germ layers — the current gold standard test for determining if stem cells are truly embryonic. If the doubters are proved wrong, an interesting question is raised: why does breast milk contain these cells? Dr Hassiotou said: 'They might contribute to tissue regeneration and development of the baby or play certain roles if there is a disease'.
Even if the stem cells are found to not be truly embryonic, they may still have potential for future regenerative medicines. Dr Lyle Armstrong, researcher at the Institute of Genetic Medicine at Newcastle University, UK told New Scientist: 'It might be possible to grow these cells in culture then bank them so that if or when the mother develops some disease later in life, such as diabetes, her cells may be defrosted and differentiated into pancreatic beta cells'. Dr Armstrong still urges caution until the true nature of the cells is known.