Breastmilk stem cells pass into offspring

Breast milk is the special subject we are looking into this week, including how the cells it contains can jump into a baby's bloodstream and literally make mum part of her offspring. Chris Smith spoke to Gürkan Öztürk from Instabul Medipol University about this work. Before that, Julia Ravey explains the rise of online sales of breast milk, and a slightly surprising consumer group…

Julia - I am perusing the milk aisle in my local shop. Oh, there is actually spilt milk on the floor and no one's crying - good to see. For me, I'm not the biggest dairy drinker. I actually don't drink dairy at all. So for me, I like to go for an oat milk or a soy milk, but you know, I know people do like cows milk as well. But how do you feel about human milk?For some people it's right up their street...

JJ - I guess people know me as the breast milk bodybuilder.

Julia - Recently, a somewhat novel market has gained traction -  individuals selling human milk online. People's motivation for buying this body fluid vary, and we'll hear more from the breast milk bodybuilder later on in the show. But at the Naked Scientists, we thought -  how easy is it to get human milk delivered to your door? I took to the internet to find out... Let's see what this brings up. Human milk for sale. I can see some container bags with what looks like milk in them -  Breast milk, healthy. Let's have a look and see if I can actually get some of this. Buy it now. And this is with second class delivery, so it will arrive in approximately two to five days time. I'm going to contact the buyer to see if I can get it a little bit quicker. Oh, okay, that's sorted then. Paid for, and it should be arriving tomorrow. And once this arrives, I'm going to take it round to the lab to analyse it to see what is actually in this milk and is this method of transport safe? I honestly didn't think it would be that easy to get. Let's see what happens tomorrow.

Chris - Pretty surprising how straightforward that purchase was, isn't it? But what is it about human milk that's made it so desirable? We know from population studies that having this milk early in life benefits infants and could affect health later in life too.

Julia - This milk has been honed by millions of years of evolution to provide newborns with a healthy start in life. As well as forging a strong mother-to-baby bond, human milk contains the right balance of nutrients so infants grow at the right rate. And it helps with the development of the immune system and the intestinal microbiome through the transfer of immune factors, as well as bacteria and other bugs.

Chris - But microbes are not the only cells that get transferred during feeding. Cells from the mother also go across and they can take up residents in the baby. Gürkan Öztürk from Istanbul Medipol university has been looking into how and why this happens. What are the cells that go across Gürkan?

Gürkan - They are stem cells. For some time we know that breast milk contains stem cells, but what happens to them in the body of the baby was not known. So in our study, we tracked them to understand at least a part of their story.

Chris - We should be clear, you were looking in animals, but animals are mammals like we are, so we can suggest that the same might be true. But what animals did you look at and how did you follow a cell out of the mother, across the breast, and then into the baby?

Gürkan - The method was quite straightforward. We have special mice who's body cells all produce a green coloured fluorescent molecule called GFP. We took normal mouse pups from a normal mother and had them breastfed by these green fluorescent protein-producing foster mothers. The idea is any cell in the foster mother's milk would be labeled with this green fluorescents. So after pups are fed with this breast milk, we were able to track down GFP-labeled cells in the growing pups at certain intervals with advanced microscopy. And we found them. We confirmed what we observed under microscope with molecular techniques and the breast milk cells were all around the pups bodies.

Chris - Where in the body did they go, these glowing green cells?

Gürkan - Practically, we came across these cells in many parts of the animals, including blood and with the highest amount in the bone marrow. However, our aim was to look at one of the most difficult parts of the body to penetrate -  the brain. Because the brain is normally protected from intrusion with a special barrier. Nevertheless, they were there, and they had differentiated became neurons and support cells, namely glial cells.

Chris - Have you tested out how long these cells persist for? Do we know once they're in the infant, how long they're likely to stay viable for?

Gürkan - In the mouse experiments, we found these cells living up to a year. But this was the maximum time we kept. So it's halfway to their expected life duration actually. So I think, unless there is a host versus graft reaction that is brain tissue rejection reaction, there is no reason why these cells should die. So what's the use of this cells? It's a very interesting question. First of all, besides these stem cells, breast milk also contains immune cells. By giving these immune cells to the baby, it is quite understandable that the baby is supported immunologically by the mother. But stem cells are quite curious because we have some new findings, additional findings in other experiments, that showed that these cells lodge into the bone marrow and somehow they are mobilised to injury sites. In another study we created stroke in the animal and when we inject breast milk stem cells, these cells aggregated in the site of injury and took part in the repair process.

Chris - My final question is one common practice is that if a mum can't use her own milk in a baby - and we see this in our hospital quite often where we've got a baby needs some donor milk - we will go to another mother and get some breast milk from her. If you do get milk from a mum that's not your own, does that make a difference? Do you end up with someone else's mum being part of you?

Gürkan - To me, it sounds like a kind of kinship. You and the other baby who shared your mother's breast milk have the original maternal cells that came from your mother. Very interestingly, in Islam there is a concept of breast milk siblings; any babies who are fed by a mother are considered to be breast milk siblings. They are like sisters and brothers. They cannot even get married to each other. So this is quite a curious case. I think by understanding more and more about these breast milk cells, we will be defining a new kind of kinship, not only in the brain, maybe in other tissues and organs.

Chris - Amazing. And I suppose you could say if you end up with bits of your mum in your brain that's "food for thought", isn't it? Thank you very much, Gürkan Öztürk there