so culture just means growing cells
there are certain basic nutrients that
all cells need just the same way that we
all need to eat food but certain
specialized cells will also need
specialized conditions we provide them
with nutrients and the conditions they
need just to keep them happy and all
that taken together is what we call it
cell culture one of the biggest problems
we have when we grow cells is the danger
that they could get contaminated
unfortunately the nutrients and the nice
conditions which are perfect for growing
cells are also perfect for growing
bacteria once it gets into a tissue
culture dish can grow very very quickly
and within a day or two will completely
overtake the culture and eventually kill
us hours
as long as we're careful we don't lose
many cells to contamination but when it
does happen it can be really frustrating
that can be many weeks of work
completely lost everything that ever
comes into contact with the cells it's
very clean and sterile even the air that
the cells are exposed to needs to be
filtered to remove bacteria once some
things come into contact with the cells
or come into contact with the air we
throw it away or restyle eyes it we
don't reuse things
the way that we look at the self to save
that healthy there are sophisticated
tests that you can do but the main way
really is just looking at them by eye
down the microscope when you've worked
with them for several months you can
very quickly tell if they have a problem
embryonic stem cells have a natural
ability to change to differentiate into
specialized cell types and if you want
to keep them growing as unspecialized
embryonic stem cells we need to find
ways of restraining that natural
tendency but we can do this because we
can control the environment the cells
are exposed to we can use special
chemicals these are the body's own
natural chemicals which have the effect
of telling the cells to remain as
unspecialized embryonic stem cells and
stop them from changing and this is
really useful for us in fact it's the
critical thing that allows us to grow
embryonic stem cells in culture now of
course there are also times where we
want to change the embryonic stem cells
into more specialized cell types we try
and find different conditions or
different chemicals which will guide the
cells to change in the direction that we
want so the way that we work out what
these conditions are is part just trial
and error but we can also get clues by
looking at the tissues that these cells
would normally reside in and working out
what the local environment is we just
have to try lots of different things we
have to do lots of experiments and when
we do see a condition that seems to do
what we want to the cells it's important
to keep repeating that to check that
that effect can be reliably used over
and over again
when we're trying to turn themselves
into particular cell types one problem
is knowing we've actually been
successful in making the type we're
interested in you might think that you
can identify just by looking it's true
that different cell types do have
characteristic shapes so neurons will be
very long and thin for example some cell
types you really can't identify by eye
we try and make use of characteristic
proteins for example a pancreatic cell
will make the protein insulin so if we
can detect insulin in a cell that gives
us a big clue that we've managed to
successfully make cell from the pancreas
so what we're trying to do more and more
these days is to find ways of
identifying with cell types while the
cells are still growing in culture one
thing we can do is make use of a special
protein which is a fluorescent protein
this is a protein that wouldn't normally
be found in the cell but it's completely
harmless so we take the gene that codes
for that fluorescent protein and put it
into the cells own DNA in such a way
that only gets switched on and starts
making this glowing protein when the
stem cell turns into that particular
cell type
so this is really useful because it
means not only can we identify but we
can also purify them because we can use
special machines which can detect the
fluorescent cells and pull them away
from the other cells so we entered with
a pure population of the specialized
cell type
with cell culture what we find is that
cells can not only survive in gray but
retain the characteristics they have in
the body and this means that we can
directly observe how the cells behave
how they respond to their environments
and this really gives us a direct
insight into how these cells decide what
living to do this is what I think is
really fascinating
you