my name is Lynda Bonewald.
And I'm from the University
of Missouri at Kansas City.
And the title of my
talk is The Osteocyte.
First, I would like to give you
an outline of the presentation.
I'll talk about
osteocytes in history,
their first proposed function,
that of osteocytic osteolysis,
their second proposed function,
that of mechanosensation,
then about how osteocytes can
serve as secretory cells regulating
such as sclerostin and RANKL, fifth,
how osteocytes are endocrine cells
that can target kidney and muscle.
And finally, I will summarize
the functions of osteocytes.
Now, there are three
types of bone cells.
There are the osteoclasts
that resorb bone
and the osteoblasts that make bone.
And then there is the third the
cell type called the osteocyte.
Osteoclasts and osteoblasts
are defined by their function.
Osteoclasts resorb bone
and osteoblasts make bound.
However, osteocytes are
defined by their location.
So this implies a lack of
knowledge regarding their function.
This slide shows osteocyte ontogeny.
The osteocyte is descended
from the pre-osteoblast, which
differentiates into the
And by some unknown mechanism, some
of these cells become osteocytes.
And then once they're surrounded by
osteoid, they begin to mineralize.
And once surrounded by mineral,
they are called mature osteocytes.
So osteocytes make
up over 90% to 95%
of all bone cells in
the adult skeleton.
And they express these long
dendritic processes that we think
play a role in
communication and viability.
And the interesting
thing about these cells
is that unlike osteoclasts that
may be viable for days and blasts
maybe weeks, osteocytes are viable
for decades in the bone matrix.
This slide shows the osteocyte
inside of a bone.
And this was taken from a mouse
in which they tail vein was
injected with Procian
red, a small dye.
And what you can see is that
the dye has totally penetrated
This shows that the circulation
can reach the osteocyte netowrk
and that anything that
is made by osteocytes
can reach the circulation.
This is further
emphasized by this image.
This is a resin cast acid etched
bone sample where all of the pores
in the bone are filled
with resin and then
acid is used to remove the
surface of the mineral.
And what this reveals
is a blood vessel
running through the bone
and an osteocyte lacunae.
And what you can see is that
these are intimately connected,
suggesting an intimate
connection between the osteocyte
lacuno-canalicular our system
and the vascular system.
This is a drawing of the
osteocyte, shown in the middle.
It's connected to and communicating
with other osteocytes.
with the vasculature,
as shown with the blood vessel.
And they can extend their dendritic
processes into the vascular space.
Not only that, osteocytes
can communicate with cells
on the bone's surface, such as
osteoblasts or lining cells.
And they can send their dendritic
processes into them marrow space.
But I'd like to also emphasize the
perilacunar matrix as shown here.
This is the kind of lavender
shaded matrix around the osteocyte.
And I'll talk about this
in a little more detail.
So there were a number of
osteocyte pioneers in history.
And one of the earliest pioneers
was von Recklinghousen in 1851.
And he came up with the first
proposed function of osteocytes,
that as removal of their
pioneer was Herald Frost,
who talked about the mechanostat
in the skeleton and how osteocytes
After that, in 1966, Belanger
talked about osteocyte osteolysis.
Baylink about how osteocytes
could resorb and form matrix.
Moarrotti talked about
Parfitt talked about
And then Kumegawa was
the first to actually
make a movie of osteocytes in 1983.
Peter Nijweidi first
described avian osteocytes
and avian osteocyte markers in 1986.
Carla Palumbo talked
about osteoid osteocytes.
And Lance Lanyon studied
So these were there
early osteocyte pioneers.