as humans, we develop from a group of cellscause 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 embryonicstem cells, our tissues have their own specialized stem cells that can repair that specific tissuein case of injury or to replace cells that are worn out, but they can only produce cellsof that tissue, and no other tissue. for example, a muscle stem cell can only produce a musclecell, not a heart cell, that's the job of the cardiac stem cells. the scientists of this paper wondered if theremay 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 significant find because of the ethicalissues associated with studying and culturing human embryonic stem cells. but if there existedcells that resembled embryonic stem cells that could produce a variety of differenttissues, it would open up many opportunities for regenerating entire organs made with aperson's own cells, eliminating many complicated aspects associated with transplants, artificialorgans, etc. these scientists are the members of the tlstylab at the university of california in san francisco and their findings were publishedin their paper titled "rare somatic cells from human breast tissue exhibit extensivelineage plasticity" in the proceedings of the national academy of sciences in march2013.
these scientists were studying normal humanbreast tissue and were interested in seeing if this tissue contained cells that couldproduce 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 tobe different between cells that had the ability to produce cells of different organs comparedto 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 markerwas increased (cd73) and one marker was decreased (cd90) in cells that could produce cells ofdifferent tissues compared to cells that cannot. this finding gave the scientists the abilityto go on a fishing expedition to find cells
in normal human breasts that had lots of cd73and very little cd90. and surprisingly, they found some!! let's color these newly discoveredcells in red from here on. they isolated these red cells and wanted to examine them a littlecloser. - to start off, the scientists found thatthese cells contained a lot of the same proteins as embryonic stem cells so they wondered ifthey were also able to form a variety of different tissues, like embryonic stem cells. first, the scientists wanted to see if thesered 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 themuscle cells that surround the mammary glands. but the scientists took this a step furtherand injected these normal breast cells in a mouse in which the breast tissue had beenremoved. and they found that these normal breast cells produced by the red cells couldrepopulate the mammary gland and even produce milk when the mouse was pregnant! so that'sgreat! the scientists have discovered a stem cell that lives in the breast that can makebreast 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, cellsthat line blood vessels, and even uniformly beating heart cells in a petri dish!!!
to confirm that all of these different typesof cells could be produced from one red cell, instead of many red cells that can each makeone type of tissue, they took single cells, allowed them to divide and then did the sameassays looking for their ability to produce breast, pancreatic, fat, blood vessel, andheart cells! and the scientists found that a single red cell could produce all of thesetissue cells! so all of this data shows that these red cellsisolated from normal breast tissue from multiple women have the ability to produce all kindsof different cells that are perfectly functional! so next, the scientists were curious to seeif these red cells, like embryonic stem cells, could divide forever, which could suggestthat they may be on their way to becoming
cancer cells and could make it more difficultto use these cells for therapy. but surprisingly, the scientists found thatthese red cells could not divide forever, they had a very limited lifespan, unlike embryonicstem cells, and many cancer cells as well. they also had perfectly normal chromosomeprofiles. so these two aspects of their biology suggests that they are probably not pre-cancerouscells (that tend to have lots of changes at the level of the dna). so what did this study show? this study found two markers that could differentiatea cell that has the ability to make different tissues from a cell that does not: high cd73low cd90. the scientists call these cells
"endogenous pluripotent somatic cells" oreps cell. which just means that they are found in our bodies, that they have the abilityto 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 es cells: - a single eps cell can producecells of all kinds of different tissues: breast, digestive system, heart, blood vessels, andthese es cells were genetically stable (unlike cancer cells). but contrary to es cells, theseeps cells could not live forever, which, together with their stable genetic makeup, limits theirability to turn into a cancer. what does this mean for you?
this study is very significant for the worldof regenerative medicine since it provides a way to use a patient's own eps cells toproduce organs needed by that patient which could potentially be transplanted back intothe patient with low immune rejection (unlike traditional transplants) and possibly lowcancer risk. of course, much still needs to be done before we can get to that point: scientistsare going to have to figure out if other tissues also contain these red eps cells, understandtheir role in normal biology, and study how best to turn these eps cells into a desiredcell or tissue to treat a specific disease. even though no one thought such eps cellscould ever exist in the body, i mean why would we want cells that can make pancreas in thebreast? but crazy enough, it turns out that
there may be previous pathological evidencefor their existence. some pathologists have previously identified cases in which normaltissues grow in abnormal locations: for example bone in the colon or eye, liver in the gallbladder,or pancreas in the brain. this suggests that these eps cells may be present all over thebody!! so as you can see, there is still much biologythat we don't understand because of the difficulty in identifying and isolating rare cells. butwith 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 they had always wonderedabout, 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 answeredand give us powerful new ways to rethink the way we treat disease.
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