 As humans, we developed from a group of cells called embryonic stem cells. These cells can make up all of the tissues in our bodies. But once we are born, these embryonic stem cells are long gone. In place of these cells, our tissues have their own specialized stem cells that can repair that specific tissue in case of injury or to replace cells that are worn out. But they can only produce cells of that tissue and no other tissue. For example, a muscle stem cell can only produce a muscle cell, not a heart cell. That's the job of the cardiac stem cells. The scientists of this paper wondered if there may be some cells hiding out somewhere after birth that can make a whole range of tissues like embryonic stem cells. This would be a very interesting find because of the ethical issues associated with studying and culturing human embryonic stem cells. But if there existed cells that resembled embryonic stem cells that could produce a variety of different tissues, it would open up many opportunities for regenerating entire organs made with a person's own cells, eliminating many complicated aspects associated with transplants, artificial organs, etc. These scientists are the members of the Tlisti Lab at the University of California in San Francisco and their findings were published in their paper titled Rare Stomatic Cells from Human Breast Tissue Exhibit Extensive Lineage Plasticity. published in the Proceedings of the National Academy of Sciences in March 2013. These scientists were studying normal human breast tissue and were interested in seeing if this tissue contained cells that could produce a variety of different cells from different tissues. To tackle this question, they looked at markers that are located on the surface of the cell that they found to be different between cells that had the ability to produce cells of different organs compared to cells that did not have that ability, but instead could only produce one type of cell. They found that two cell markers were different between these two types of cells. One marker was increased CD73 and one marker was decreased CD90 in cells that could produce cells of different tissues compared to cells that could not. This finding gave the scientists the ability to go on a fishing expedition to find cells in normal human breasts that had lots of CD73 and very little CD90, and surprisingly they found some. Let's color these newly discovered cells in red from here on. They isolated these red cells and wanted to examine them a little closer. To start off, the scientists found that these cells contained a lot of the same proteins as embryonic stem cells. So they wondered if they were also able to form a variety of different tissues like embryonic stem cells. So first the scientists wanted to see if these red cells could produce cells of the breast tissue where they were discovered. And indeed when a group of red cells were allowed to divide in the presence of very specific conditions, the scientists observed the presence of normal breast cells in a petri dish, including the muscle cells that surround the mammary glands. But the scientists took this a step further and injected these normal breast cells in a mouse in which the breast tissue had been removed. And they found that these normal breast cells produced by the red cells could repopulate the mammary gland and even produce milk when the mouse was pregnant. So that's great. The scientists have discovered a stem cell that lives in the breast that can make breast tissue. But can it also make other tissues? Well, it turns out that they can. The scientists were able to make cells of the pancreas, lipid-filled fat cells, cells that line blood vessels, and even uniformly beating heart cells in a petri dish. To confirm that all of these different types of cells could be produced from one red cell, instead of many red cells that can each make one type of tissue, they took single cells, allowed them to divide, and then did the same assays, looking for their ability to produce breast, pancreatic, fat, blood vessel, and heart cells. And the scientists found that a single red cell could produce all of these tissue cells. So all of this data shows that these red cells isolated from normal breast tissue, from multiple women, have the ability to produce all kinds of different cells that are perfectly functional. So next, the scientists were curious to see if these red cells, like embryonic stem cells, could divide forever, which could suggest that they may be on their way to becoming cancer cells, and could make it more difficult to use these cells for therapy. But surprisingly, the scientists found that these red cells could not divide forever. They had a very limited lifespan, unlike embryonic stem cells, and many cancer cells as well. They also had perfectly normal chromosomes, or DNA profiles. So these two aspects of their biology suggest that they are probably not pre-cancerous cells that tend to have a lot of changes at the level of the DNA. So what did this study show? This study found two markers that could differentiate a cell that has the ability to make different tissues from a cell that does not. High CD73 and low CD90. The scientists call these cells endogenous pluripotent somatic cells, or EPS cells, which just means that they are found in our bodies, that they have the ability to make different tissues, and that they are not germ cells, which are eggs and sperm. By isolating and studying these EPS cells, the scientists found some similarities to embryonic stem cells. A single EPS cell can produce cells of all kinds of different tissues, breast, digestive system, heart, blood vessels, and these EPS cells were genetically stable, unlike cancer cells. But contrary to embryonic stem cells, these EPS cells could not live forever, which together with their stable genetic makeup, limits their ability to turn into a cancer. So what does this mean for you? This study is very significant for the world of regenerative medicine, since it provides a way to use a patient's own EPS cells to produce organs needed by that patient, which could potentially be transplanted back into the patient with low immune rejection, unlike traditional transplants, and possibly low cancer risk. Of course, a mission needs to be done before we can get to that point. Scientists are going to have to figure out if other tissues also contain these red EPS cells, understand their role in normal biology, and study how best to turn these EPS cells into a desired cell or tissue to treat a specific disease. No one thought these EPS cells could ever exist in the body. Why would we want cells that can make pancreas in the breast? But crazy enough, it turns out that there may be previous pathological evidence for their existence. Some pathologists have previously identified cases in which normal tissues grow in abnormal locations. For example, bone growing in the colon or the eye, liver growing in the gallbladder or pancreas in the brain. This suggests that these EPS cells may be present all over the body. So as you can see, there's still much biology that we don't understand because of the difficulty in identifying and isolating rare cells. But with all of the new technology around, it's becoming much easier to do this kind of research. So scientists are now able to go back, ask new basic questions that they had always wondered about, and have the tools necessary to get clear and important answers like never before. So simple questions that seemed impossible to answer 10 years ago can now be answered and give us powerful new ways to rethink the way we treat disease. This video has been provided to you by Eureka Science. To stay in touch with Eureka Science, like us on Facebook, follow us on Twitter, subscribe to our YouTube channel, or visit us at www.eurekascience.com. Thank you for watching.