stem cells we hear a lot aboutstem cells these days, but what are they,where do they come from and what do we reallyknow about them? inside our bodiesthere's a microscopic world, busy and complexlike the world around us. stem cells buildand maintain this world. this is a story of stem cellsand their lives inside and outside our bodies.
life begins with one cell,the fertilised egg. throughout developmentcells divide over and over again to produce the billionsof cells that make up the body. at certain stages, most cellsstop making copies of themselves and start to specialise. when we are fully formedalmost all our cells are specialised. cells are beautiful thingswhen you see them down a microscope. normally they're so minisculewe can't see them, even though they'rewhat make us.
and each type of cellhas its own characteristic. some types of cellgrow very closely together and form beautiful patterns. other types of cellwill move away from one and other. some cells become big,others are always very small. it depends on what type of cell they are. these different cell typeswork in specialised teams. some carry oxygenthrough the blood system, some do the stretchingand contracting in our muscles,
some carry messages between our brainand the rest of our body. stem cells are very special cellsthey act as a resevoir, because the specialised cells can no longer make copies of themselves. so, if they die and get used up,they have to be replaced from somewhere. and this is where the stem cells function. stem cells are usedin the blood system. we need to make millionsof new blood cells every day and these are generatedfrom stem cells.
and these cells actually livein the bone marrow. altogether a blood stem cellcan make eight different types of specialised cell. they're used in the skin. we need to make new skin cellsall the time because we're alwayswearing away our skin. and actually now we knowthey're present even in the brain. we always have to makenew stem cells, so they're not completely exhausted,
because otherwise we'd losethe capacity to make any new cells. so the stem cell has tomake a decision. every time it divides,it produces two daughter cells, and those daughter cellscan be new stem cells, or they can be specialised cells. stem cells in the adult tissuescan normally only make the type of cell in that tissue. so a stem cell in the skin,can make cells in the skin, but it can't make blood cellsand vice versa.
stem cells are already usefulin medicine. one skin stem cell alone can produceenough specialised skin stells to cover the whole body. this produced a breakthroughin the treatment of extensive burns. 1st degree burn... when a person is heavily burnt,we take a sample from an unburnt areaand we take apart the skin sample and we get the cells out of it, and we seed the cellsin a culture flask like this one.
we feed the cells with a special liquid,which is full of protein and sugar. they need to eat like you. at some point, these cells will divide,will multiply. and they will cover the entirebottom of the flask. we remove the cells usinga special chemical and we take this sheet of cellsinto the surgery room and transplant the patient with it. we can do only part of the skin today, which means we can dothe outer most layer of the skin,
which is very important, because withoutthis layer you wouldn't be able to survive. however, we cannot reconstructsweat glands our hair follicles. so these burnt patients have hadtheir lives saved by stem cells, but they have no hairand they don't sweat. that is obviously a problem. they are alive, but i can't saythey have a normal life. that's why many laboratoriesare trying to understand how the skin is built to be ableto reconstruct it in the lab, so we can improve the lifeof these patients.
stem cells are also used to treatpatients with blood disorders, such as leukaemia. a transplant of justa few blood stem cells, is enough to repairthe entire blood system. stem cells for specific tissuesand organs can only make the cellsof that tissue. we know there are stem cellsin skin, blood, guts and muscles, but we don't know whetherother organs have their own stem cells, or how useful they will be.
back along the chain of development,there's another kind of stem cell. it's controversial. it can becomeany specialised cell. the embryonic stem cell. this cell comes from a blastocyst,the stage of development before implantation in the uterus. for fertility treatment, blastocysts areproduced in the laboratory. if they are not used for a pregnancy,they can be donated for research. in the early embryo,there's a group of cells that can give rise toall the tissues of the body.
these are the cellswe're very interested in because we know that we cantake the cells from the early embryo and grow them in culture,and maintain them in a state where they can contributeto all the tissues. what we're seeing hereis the blastocyst stage of development. it's smaller than a pin head. you can't see it withoutthe microscope. so at this stage, the cellsin the embryo - these are the cells - they can make any tissue at all.
what we have to do, is isolate these cells. one way is we can removethe trophectoderm cells so that we're just left with a cleaninner cell mass. so we can grow these in culture,and they'll multiply until we have lots of these cells that still have the capacity to form any tissue at all. embryonic stem cells can becomeheart, blood, brain or skin cells depending on the way they are grown.
these stem cells haveturned into heart cells. when you're working with stem cells,you're always observing the cells and you're trying to understandhow it is they can do what they can do. you're trying, actually, to make them dowhat you want to do. it's almost like a battle of wills. a stem cell goes through a long series of decisions to become a specialised cell. a combination of internal and externalsignals guide each stem cell along the path towards specialisation.
these signals are normallyprovided by the body. by figuring out how to recreatethese signals in the lab, scientists aim to grow pure populationsof almost any cell type. the challenge to us is to understandeach decision and how it's controlled. and then how to provide those signals, to impose the direction on the sytem. and once we get to a pointwhere that begins to happen, then you suddenly see thatyou could use it to address medical conditionsand problems.
work that we havebeen doing recently has been focussed on tryingto make stem cells for the brain from embryonic stem cells.and it turns out we're able to do this. these neural stem cellsare now no longer able to make all cells, they can only make three types of cells,the three types that exist in the brain. so this is an important first stepin creating a useful and powerful system, that can both be applied for drug screeningand perhaps in the end for transplantation. these lab-grown human cells,produced in large numbers, provide improved modelsfor testing new medical treatments
and may reducethe need for animal testing. the same cells may help us understandwhat goes wrong in complex diseases, like alzheimer's, parkinson'sand diabetes. diabetes is a chronic diseasedefined by high blood sugar levels that stay high just becausethere is not enough insulin. we know that the insulin is produced bycells in the pancreas. we call them beta cells. transplantations of those cellsare now done in clinics. those cells are isolated fromdonor organs.
after transplantation with those cells,you can normalise diabetes. you can correct diabetes. the major obstacle to beta celltransplantation in diabetes is the shortage of donor cells. we can transplantonly 25 patients per year, while there are more than 50,000 patientsin belgium that are treated with insulin. we have to look for other techniques to produce insulin-making cellsin the laboratory. what the researchers try to do
is first examine this path,this evolution between the embryonic stem celland the insulin-producing beta cell, and then to also try to isolatethe different stages, the different kind of stem cellson the way to beta cells. if one can then isolate themand let them grow in the laboratory then you can make as manyinsulin-producing cells as you want. and that's the goalof many investigators in the world. the embryonic stem cell areais a very exciting area. it really has opened a new world,that of regenerative medicine.
we have now bridges betweenall the laboratories that have a particular expertise. working together,we will be in a good position to examine, to investigateits enormous potential, but the enthusiasm should not coverall the technical and scientific questions and obstacles that exist and that will haveto be studied very carefully. stem cell research is a fast-moving field. around the world,new findings are constantly reported,
creating new questionsand fresh challenges for scientists seeking to harness these cellsand to shape future medicine. so cells are the building blocksof the tissues and organs of the body. and many people are interested in this. what captured my imagination,was when i realised that in development, cells actuallyhave to make choices and decide to becomedifferent types of cell, and understanding how that is controlled,how that decision is made... if you could understand that,it seems to me,
then you would understandthe most important thing about life.
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