Brain cells at the breaking point
Fracture study could lead to insights into traumatic injury
By Laura Sanders
Rigid pathways in brain cell connections
buckle and break when stretched, scientists report, a finding that could aid in the
understanding of exactly what happens
when traumatic brain injuries occur.
Up to 20 percent of combat soldiers
in Iraq and an estimated 1. 4 million U.S.
civilians sustain traumatic brain injuries each year. But the mechanics behind
these injuries have remained a mystery.
New research presented February 19
shows that forces similar to those that
cause traumatic brain injury can damage
tiny conduits called microtubules.
Microtubules extend down the length
of axons — which transmit electrical sig-
nals in brain cells — serving as “superhigh-
ways of protein transfer,” said Douglas
Smith of the University of Pennsylva-
nia in Philadelphia, who conducted the
research with colleagues. Brain cells rely
on microtubules to move important cel-
lular material out to the ends of axons.
Sudden forces cause structures inside
axons to break (arrow), leading to dam-
age, a new study shows.
stretched brain cells growing on a silicone membrane, the microtubules
inside the axons immediately buckled
and broke, spilling their contents.
“This disconnection at various dis-
crete points spells disaster, and things
are just dumped out at that site,” Smith
said. “Microtubules are the stiffest com-
ponent in axons, and they can’t tolerate
that rapid, dynamic stretch.”
Like Silly Putty pulled slowly apart,
axons can adjust to gradual stretching,
Smith said. But sudden forces, like those
that happen in blasts and collisions, can
cause the Silly Putty to snap.
In their lab dish experiments with
brain cells on silicone, the researchers
were able to minimize microtubule damage with a drug called Taxol, commonly
used to treat cancer. But it’s too early to
say whether the drug would work in people with traumatic brain injuries.
Currently, traumatic brain injury
research is in “the abyss between bench
and bedside,” Manley said. So figuring out exactly what happens in traumatic brain injuries could lead to new
approaches to treatment.
Stem cells fuel
Mouse study also shows
role for gene in malignancy
By Laura Sanders
Some self-renewing stem cells may play a
role in prostate cancer, and a certain gene
in these cells contributes to the malignancy, research presented February 20
suggests. Prostate cancer is the most
common malignancy in men in Western
nations, affecting one in six men.
Like many other tissues in the body,
prostate tissue is made up of several different kinds of cells, including a class
called basal stem cells. Normally these
cells divide to replenish prostate tissue,
but sometimes they become cancerous.
Instead of producing normal cells, these
stem cells lead to tumors.
“Think about cancer as a disease of
stem cells,” said study coauthor Owen
Witte, a Howard Hughes Medical Insti-
tute investigator at the University of
California, Los Angeles. Mutations can
cause “normal stem cells to lose their
regularized behavior and instead turn
into an incipient cancer.”
Witte and his colleagues wanted to
determine which class of cells gener-
ates prostate cancer in mice. They sepa-
rated mouse prostate cells into different
groups based on type, then introduced
mutations often found in prostate can-
cers. Then the researchers implanted the
cells back into mice one type at a time.
Basal stem cells outpaced the other
groups by far in their cancer-forming
ability, the researchers reported Febru-
ary 9 in the Proceedings of the National
Academy of Sciences. Earlier studies sug-
gested that the same thing might also be
happening in human prostate cancers.