Stem Cell Universe with Stephen Hawking

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I have spent my life

exploring the mysteries

of the cosmos.

But there's another universe

that fascinates me,

the one hidden

inside our bodies...

...our own personal galaxies

of cells.

Today, we are on the brink

of a new age in medicine,

an age where we will be able

to heal our bodies

of any illness,

all because of cell inside us...

...which have special powers.

They are called stem cells.

These microscopic

miracle workers

are, however, barely understood.

Implanting them into our bodies

could unleash biological mayhem.

Are stem cells magic bullets

or ticking time bombs?

I haven't lived

a very normal life.

Since my 20s, I haven't had

to deal with the distractions

that come

from being able-bodied.

I have led a life of the mind.

Stem cells may give you

that same freedom...

...allowing you

to pursue your wildest dreams

without ever having to worry

about the limitations

of your body.

Dr. Robert Lanza

is one of the pioneers

of stem cell therapies.

He is already using them

to help patients regenerate

damaged body parts.

Right now,

we're in clinical trials

to try to treat blindness

using retinal cells

that were generated

from stem cells.

We've also been able to create

entire tubes of red blood cells

that transport oxygen just like

normal, transfusable blood.

Robert's work developed

from studying

how stem cells create

not just body parts,

but entire bodies.

They do this for all of us

when we start out

as nothing more

than a fertilized egg

floating in the womb.

So, imagine I'm floating

down the fallopian tube.

And first, there's one of me,

and then there's two of me.

Then there's gonna be four of me

and eight of me.

And we continue on dividing.

And eventually,

when I get downstream,

I'll be a ball

of about 100 cells.

These embryonic

stem cells are blank cells.

They have not yet become

a specific type of tissue.

But soon,

they start transforming

into specialized bone cells,

muscle cells,

and nerve cells.

Nine months later,

they form a complete person.

Once we are born, however,

these blank embryonic stem cells

disappear.

We lose the power

that they alone possess

to regenerate all of the tissues

in our bodies.

Robert is working

on restoring that power.

So, when you think

of a regular cell,

whether it's a skin cell,

a heart cell, or a blood cell,

it turns out

that that cell carries out

a very specific function.

And it carries out that function

for its entire life.

So, the question is,

what tells that cell what to do?

And that's where DNA comes in.

The way DNA is packed

into the nucleus of each cell

determines what function

it's going to have.

DNA's long double helix

is wound around a huge number

of tiny, molecular balls

in a structure called chromatin.

As we grow in the womb,

certain proteins interact

with the chromatin

of a blank embryonic cell

causing parts of its DNA

to become unspooled.

The parts that are unspooled determine

the type of cell this is going to be.

A heart cell will have

one DNA arrangement.

A skin cell, another.

This process

of cell specialization

appeared to be irreversible...

Until a breakthrough experiment

in 1962.

What scientists did

is they actually took

an adult cell in the case

of a frog, an intestinal cell,

and they put it

into an empty egg.

And what had happened

is that that egg

actually acted

like a little time machine

and brought the DNA

back in time to a point

where it could actually generate

an entire tadpole

and then, eventually,

an entire frog.

Biologists now believe

key proteins in the egg

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