and they're talking about some new medical technology,

Some breakthrough treating congestive heart failure or regrowing muscle tissue in wounded soldiers.

I bet you that that story is going to mention that this new type of therapy uses stem cells.

And I bet you, like most people, are going to listen along and just go [nods agreeably]

Without actually knowing what stem cells are, because who has time to know what stem cells are?!?

Today, we are making time.

You have lots of different types of cells in your body.

You've got muscle cells, and skin cells, and liver cells, and brain cells,

Most of these cells have to be replaced every once in a while.

Your tastebuds, for instance, are replaced every 10 days or so,

Skin cells are replaced every couple of weeks, and liver cells turn over every 300-500 days.

The cells that are doing the replacing of the old cells, and the repairing of the damaged tissue are adult stem cells, also called somatic stem cells.

The different sort of cells, skin cells, liver cells, retina cells, muscle cells and intestine cells,

They all have very specific jobs and they're built in very specific ways to do those jobs.

Different shapes, sizes, contents, mean you can't just stick a muscle cell into a damaged liver an expect it to start breaking down your alcohol for you.

Somatic stem cells, on the other hand haven't decided what the heck they're gonna be.

They're undifferentiated. They haven't specialized yet.

Like a college freshman, or, let's face it, a recent college graduate. They have no idea what they're going to do with their lives.

but just like there are different types of college graduates, there are different types of adult stem cells.

Some can become more different kinds of things than others.

Pluripotent adult stem cells can become many different types of cells all over the body,

However, they're really hard to track down because there are so few of them in each organ or tissue.

There also multi potent adult stem cells which are more common in the body,

but restricted in the kind of cell they can become

it is kinda like the difference between graduating from trade school where you have been trained to do a few different possible jobs

and graduating with a degree in philosophy or something

equally unprepared for all jobs

so yeah , stick a Pluripotent cell in a damaged liver

and it just happily becomes a liver cell

pretty cool

but there are some even better types of stem cells to be had

embryonic stem cells

which are also Pluripotent

these are the cells inside a human embryo when it is a blastocyst

basically just a tiny nugget of human cells four or five days old

which is destroyed in the process of removing the stem cells from inside it

these embryonic cells are obtained from in vitro fertilization clinics

that fertilize eggs outside of the mother's body for couples who are having trouble conceiving

naturally, these clinics have some left over fertilized eggs

so with the donor's permission they are given to scientists doing stem cell research

now the main advantage of the embryonic stem cells is that

while adult stem cells can be grown in culture for time

meaning they can be made to multiply over and over in a nutrient solution

they can't grow as long or as fast as the embryonic stem cells

which can be maintained indefinitely into the right conditions

after just six months in culture , a single wad of 30 embryonic stem cells will have yielded millions of stem cells

which can go on to develop pretty much into any type of cell in the body

also adult stem cells if used in some sorts of transplant therapies are more likely to be rejected than embryonic stem cells

stem cell research is currently pretty hopin

embryonic stem cells are being used by researchers all over the world

to figure out how to repair or replace damaged cells and organs and create new drugs

but regulations have taken their toll

there are only about thirty five stem cell lines or families of identical pluripotent stem cells that are available for federally funded research in America

whereas Europe has a couple thousand

so there , now you never have to " nod along " your way through another news report about stem cells again

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transcription by Dr.A