Breast milk stem cells may be incorporated into baby

It was discovered seven years ago that human breast milk also contains a kind of stem cell. The question was whether these cells do anything useful for the baby or if they simply leak unavoidably into breast milk.

Stem cells have the unusual ability to regenerate themselves and develop into a variety of tissues. Several sources of stem cells are being developed for therapeutic use, including embryos, umbilical-cord blood and adult tissues.

The latest findings, presented at the National Breastfeeding and Lactation Symposium in London last week, suggest that in mice at least, breast milk stem cells cross into the offspring's blood from their stomach and play a functional role later in life.

Foteini Hassiotou at the University of Western Australia and her colleagues showed this by first creating genetically modified mice whose cells contain a gene called tdTomato, which makes them glow red under fluorescent light.

The female mice were mated but then after giving birth were given unmodified baby mice to suckle. So any red cells that ended up in the pups must have come via the milk.

Breast milk is known for being full of goodies – but could that include stem cells from mum that go on to transform into parts of the baby's body? Preliminary evidence has shown this happens in mice, suggesting it also does in people. Sure enough, when the offspring reached adulthood, red cells were found in their blood and many of their tissues, including the brain, thymus, pancreas, liver, spleen and kidneys.