2990 Microsurgery.qxd - O'Brien Institute

Scientific Research
Bernard O’Brien Institute of Microsurgery
inadequate regeneration of axons (nerve fibres),
and/or deterioration and scarring of the target
prior to reinnervation.
The orthodox method of nerve repair used in
clinical practice is by direct suturing of the cut
ends of the nerve. Alternative methods of nerve
repair include:
(a)
(b)
(c)
(d)
end-to-side repair, in which the distal end
of a cut nerve is directly apposed to a
healthy nerve,
neurotisation, in which the proximal end of
a cut nerve is implanted directly into the
target muscle,
grafting, in which various tissues are used
to bridge the injury,
entubulation repair.
Entubulation repair of transected nerves is the
standard model for studying peripheral nerve
regeneration and recovery. It involves removing
a small length of nerve, thereby leaving a gap
between the proximal and distal ends of the
nerve. This gap is bridged by plugging these
stumps into either end of a hollow silicone tube
which spans the gap, thus forming a sealed
chamber. Within this chamber, proteins (survival
factors, etc.) and cells that collect in response to
nerve injury can be studied, test substances can
be administered and their effects on the nerve
repair process determined.
Improving nerve repair with
Leukemia Inhibitory Factor (LIF)
Over the last four years this Institute has had
great success repairing cut or crushed rat nerves
in conjunction with the growth factor known
as LIF (leukemia inhibitory factor). The nerves
that regenerate are stronger and transmit
messages faster and the muscles they supply
do not wither as much and eventually their
function is much improved.
Over the past year we have been trying to
modify or refine LIF’s use so that it may be
more useful in the human setting. We have
investigated answers to the following questions:
1. How much LIF do we need, and what is
its cost?
2. After a nerve is severed, when is the best
time to administer LIF?
3. For how long is LIF required by nerves to
adequately do its job?
4. Does LIF do an even better job if added
with other nerve stimulating factors?
5. What is the most convenient way of
administering LIF?
At this stage we can say that LIF should be used
in very small doses for very short periods. It is of
benefit whenever it is given after nerve trauma,
the earlier the better, and is best given as a
cocktail with other growth promoters.
We have also been looking at more scientific
aspects of its use. We wish to know how LIF
works on our nervous system and how safe it
is. We have also been trying to answer the
following questions:
1. Are more nerve cells actually surviving due
to LIF?
2. Are they re-growing faster, bigger or in
greater numbers?
3. Are they being directed more efficiently to
their targets?
4. Are the muscles being kept healthier by the
LIF until nerves can get back to them?
This is an exciting time for this project because
we can really start to see how LIF may soon
benefit our patients. The possibility that nerves
and muscles could recover from work injuries,
lawn mower cuts or glass laceration, twice to
three times better than by current clinical
techniques methods, is exciting news. This
is the type of result we are striving for.
Leukemia Inhibitory Factor (LIF)
is an autocrine survival factor for
Schwann cells
Schwann cells are cells which line the nerve
axons (see attached Figure). They play a
major role in promoting nerve survival and
regeneration after injury by neurotrophic
factors, extracellular matrix components and
cell-surface adhesion molecules to promote
axon regeneration. The aim of this study was
to determine whether the enhanced recovery
of muscle function observed when LIF was
administered at the time of nerve repair was,
in part, due to an effect on Schwann cells at
the injury site. Following nerve transection, LIF
is up-regulated by Schwann cells at the injury
site. The LIF receptors (LIFRb and gp130) are
also up-regulated at the nerve injury site but
their cellular localization and consequent
function have not been fully characterized.
We investigated whether LIF could act to
regulate the Schwann cell response.
Rat sciatic nerve Schwann cells were cultured
under various conditions and mRNA extracted.
RT-PCR revealed that Schwann cells express
mRNAs for LIF and the LIF receptor components
LIFRb and gp130, and therefore have the
potential to respond to LIF. Since Schwann cells
produce large amounts of LIF in culture, we
determined the role of LIF by either adding more
LIF to the cells or by blocking LIF activity with
the soluble LIF receptor LIFBP. LIF was found to
act as a proliferative factor and a survival factor
for Schwann cells. The blocking of LIF activity in
the cultures also appeared to have an effect on
cell morphology, which could be explained by
LIF having an effect either directly on cell to
substrate adhesion or it may simply be a
phenomenon of reduced cell viability.
Our data suggest that Schwann cell survival and
morphology following nerve injury is likely to
be modulated by LIF, suggesting a LIF-initiated
autocrine survival loop. We now wish to
determine the effect of LIF on the expression
of Schwann cell proteins which may play a
role in the promotion of nerve regeneration.
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