Multiple sclerosis is an autoimmune
condition in which components of the immune system mistakenly attack
the fatty lining around nerves in the brain and spinal cord. The
majority of drugs currently used to tackle the symptoms of MS,
therefore, focus on preventing this destruction by targeting the immune
system. But a team of scientists think they may have found a different
approach to treatment: targeting stem cells already present in the patient’s nervous system.
Photo credit:
A 3D rendering of microscopic human nerve cells showing axon
dendrites and myelin sheath. 3Dme Creative Studio / Shutterstock
Stem cells, commonly associated with embryos, exist in human adults
as well—it is just more difficult to activate them. Stem cells are
‘blank canvas’ cells capable of becoming any type of cell in the body,
such as muscle, brain tissue or, in the case of this study, the myelin
sheath.
The myelin sheath
is a fatty lining around the nerves in the brain that protects and
insulates these neural pathways. A sufferer of multiple sclerosis has
this protective myelin sheath stripped away, exposing the nerves
underneath. These nerves get weathered and damaged without the myelin
sheath and, as a result, the patient suffers from shakes and numbness.
Designua via Shutterstock
The team, who published the study in Nature,
wanted to find a drug that would encourage stem cells in the brain and
spinal cord to become the type of cell that produces myelin, which are
called oligodendrocytes. With more myelinating cells on board, the
damage to nerve cells should slow down, and hopefully further damage
will also be prevented. Ideally, the candidate drug would even start to
reverse paralysis in multiple sclerosis sufferers.
The two drugs used in the trial were miconazole, which is found in
over-the-counter antifungal treatments such as athlete's foot, and
clobetasol, which is used to treat skin conditions such as eczema. These
might seem like unlikely candidates to coax stem cells to become the
important myelin cells in the brain but, of course, there is method
behind the madness. The team tested the effects of different drugs
(727 to be precise), which all had a history of use in patients, on
laboratory-grown stem cells called ‘oligodendrocyte progenitor cells,’
or OPCs for short. Out of all the drugs investigated, the two drugs
selected—miconazole and clobetasol—were best at stimulating the
conversion of these blank stem cells into myelinating cells.
The effect of these versatile drugs on restoring myelin in the brains
of mice with multiple sclerosis-like disease was remarkable. As Robert
Miller, a neuroscientist at Case Western Reserve, said: "It was a
striking reversal of disease severity in the mice."
Whilst this was very promising with mice, it will be more difficult
to evaluate in humans. It is extremely difficult to assess the reversal
of brain damage and restoration of myelin reliably in living
humans. Another hindrance in the evaluation of recovery is that progress
takes a long time. It could take years, not months, to see the effects
of myelin restoration, which means that trial studies will take a while
and results won’t be quick. However, the team is enthusiastic that they
can develop optimized versions of these drugs in the future.
The public are advised not to take the current versions of these
drugs to alleviate the symptoms of multiple sclerosis. The forms of
drugs being tested have not been refined for the purpose of remylenation
yet.
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