We have all probably heard about the benefits of breast milk for your baby as opposed to some other source of nutrition. This list of benefits is extensive: antibodies, better microfloral adaptation throughout the gastrointestinal tract, it helps you get your figure back, lower rates of illness in breast-fed babies, better for the environment, and so on. However, this long litany of benefits, and do not get me wrong, I am not knocking the benefits of breast-feeding, does not include one other benefit, and that includes a dose of breast-specific stem cells. Preliminary evidence has shown that mouse pups take in stem cells from their mother during breastfeeding, suggesting that the same thing might happen in humans.
Several years ago, it became clear that human breast milk contains a breast-specific kind of stem cells. This remarkable finding however did not answer the question of whether these cells coincidentally leaked into breast milk or they do anything useful with respect to the breast-feeding infant.
A presentation at the National Breastfeeding and Lactation Symposium in London last week presented data that suggests 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 from the University of Western Australia and her coworker used genetically modified mice whose cells contain a gene called tdTomato, which glows and intense shade of red under fluorescent light. The red-glowing females were mated and gave birth to mouse pups, but they were then presented with mouse pups from mothers who were genetically unmodified. Thus any red-glowing cells in these unmodified pups must have come to them from their mother’s milk.
When the these mouse pups that had been suckled by the tdTomato-expressing mothers grew to adulthood, assays of their tissues showed that red-glowing cells were found in their blood and the brain, thymus, pancreas, liver, spleen and kidneys. Hassiotou’s team also discovered that the breast-specific stem cells had differentiated into mature cells. Those red-glowing cells in the brain had the characteristic shape of neurons, those cells in the liver made the liver protein albumin, and those in the pancreas made insulin. According to Hassiotou, “They seem to integrate and become functional cells.”
What, precisely, is the role of these cells in the life of mice? Do they play a role in normal growth and development, or could they help to make the offspring tolerant to its mother’s cells and proteins, to reduce chances of an allergic reaction to her breast milk? “There must be some evolutionary advantage,” says Hassiotou.
According to Hassiotou, since her work and that of her colleagues clearly shows that these breast milk stem cells can differentiate into several different types of tissues makes it more likely they could be used for therapeutic applications. Chris Mason of University College London adds: “If these intriguing cells are functional, they could be a novel option for producing future cell therapies.”
Breast milk stem cells seem to have less capacity for unlimited cell division than embryonic stem cells. “But that’s actually a good thing,” says Hassiotou, because they do not form tumors when injected into mice. Therefore they may be less likely to trigger cancer if used to treat people.
Hassiotou points out that this kind of work cannot be done in humans, but she is planning to repeat it in a non-human primate species known as macaques.