Thanks Willie very interesting, unfortunately my work computer has a filter that doesn't allow me to view these photo.  Sound like you are having fun.

 

poyap

mol william <w_mol2003@yahoo.co.jp> wrote:

Stem cells are hot topics of modern, medical, scientific
research. Various methods of cloning & preparation of stem
cells has been developed. However, the ultimate goal of
such research is to achieve tissue and/or organ
regeneration in vivo or in vitro. To do that we have to
precisely guide the differentiation (fate) of the stem
cells, otherwise they would become useless tissues
(teratomas) or dangerous tissues (cancers). The mechanisms
or the factors that guide or determine cell
differentiation is complex. However, to simply we could
say:

1. A cell's interaction with the extracellular matrix via
adhesion molecules
2. Cell-cell interaction also via adhesion molecules
3. The concentration & the precise timingly release of
soluble factors into the extracellular space & the precise
interraction with their ligands (receptors) of which their
expression is regulated precisely resulting in
communication between cells & guides normal cell
differentiation.

A stem cell becomes a certain cell because of the:
1. Expression of certain combination of markers
2. Has certain function (releases certain factors or
produces certain proteins, or has highly specialized
function-nerves)
3. May or may not have a distinct cell morphology to the
originally, transfered stem cell

Interesting, a cell in a certain part of the body has a
system of knowing its exact location and how to interract
to it. This is achieved by the regulated expression
patterns of HOX gene complexes
(http://en.wikipedia.org/wiki/Homeobox). Also of interest
when a cell is removed & grown in the lab, for a certain
period of time, the cells:
1. lose their cell markers (identity)
2. May loose their function & even morphology
3. The pattern of HOX gene expression is lost or becomes
very different to that of the original in vivo pattern

This simply means the cell has become a totally different
cell because of the different environment, without the
influence of other cells & the factors they produce. Such
cells cannot be transfered back to the body because of the
risk of rejection, infection & cancer formation. Current
technology cannot totally overcome these problems yet. So,
the alternative thing to do could be to directly transfer
stem cells to the body & try to guide their
differentiation (fate). However, this is currently in its
experimental stage.

When a stem cell is transfered, first they have to be
labelled with a dye (eg. DiI). Second, transfered using
various surgical methods (injection, attached to
artificial collagen & applied etc.). Third, a biopsy is
done to visualize the labelled cells & to prove that it
poses the markers (immunohistochemistry) of the cells it
is suppose to differentiate to.

There is a controversy that sometimes the transfered stem
cells don't just differentiate into the desired cell type
(trans-differentiation) but they fuse with the local,
residing adult cells, making the procedure of stem cell
transfer a useless one because no new cell or tissue will
be formed (no tissue regeneration). After cell fusion, the
dye in the labelled stem cells will be shared between the
2 cells & then the final cell will also poses the markers
of the adult cell, making the in vivo study a confusing
one.

Finally, it would be simpler to do cell fusion studies
between stem & adult cells in the lab first (in vitro) &
then apply the knowledge to guide cell
trans-differentiation in vivo.

With that I have put 3 photo albums of the my practice
labelling of rat bone marrow cells & follow-up of
morphological changes the cells have undergone over
several days, using DiI in the CME, photo section. The
cell marker studies has not been done. The cells can be
labelled like this & then transfered back to the animal
(eg. rat). DiI is a red dye that stains cell membrane &
cytosol. Hoechst is a green dye that stains only the
nucleus. These dyes are visualized only using a
fluorescent microscope.

Thanks!

William Mol

(Sapporo, Japan)

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