The use of embryonic stem cells in medical research has been a hot-button moral and ethical debate for years — but there may be a way to sidestep the issue entirely. Scientists have now isolated embryonic-like stem cells in human breast milk.
Researchers at the University of Western Australia first found stem cells in breast milk back in 2008, but the full potential of that discovery is only now becoming clear. The team has grown lab cultures of these stem cells and discovered that they can take on properties almost like those of embryonic stem cells.
In particular, these breast milk stem cells can develop into any of the three embryonic germ layers, known as the endoderm, mesoderm, and ectoderm. In embryonic stem cells, it's from these three layers that the cells can then develop into any of the 220 different cell types found in the body. This quality, known as pluripotency, is what makes embryonic stem cells specifically so powerful as a tool in regenerative medicine.
Now it seems that breast milk stem cells could be just as pluripotent as their embryonic counterparts, with few to none of the ethical concerns that have engulfed the use of embryonic stem cells. Team member Foteini Hassiotou comments:
"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. What is really amazing is that these cells can be obtained in quite large amounts in breast milk."
This is all exciting news, but there is room for some skepticism here. The key test hasn't happened yet — and that's to inject these breast milk stem cells into mice to see whether they develop teratomas, which are tumors that feature tissue from all three embryonic germ layers. If the researchers can find that, then we really will have an adult-derived stem cell that is every bit as versatile and potent as embryonic stem cells. Such a breakthrough might not kill the stem cell debate entirely, but it would take a lot of the wind out the sails of the opponents of such research.
Assuming this research holds up, one other question to explore will be just why breast milk unexpectedly contains such pluripotent stem cells. Hassitou speculates:
"It has been shown in mice that live immune cells in breast milk pass through the intestinal mucosa into the blood circulation of the pups and engraft in various tissues. If these cells are in human milk and in such high amounts they probably have a role. They might contribute to tissue regeneration and development of the baby or play certain roles if there is a disease."