Wednesday, October 24, 2012

NEWS: Brain Police: Stem cells’ fecund daughters also boss other cells around

Originally posted by Stanford School of Medicine on Oct 22, 2012
by Bruce Goldman

Neural stem cells get plenty of good press, and understandably so. They’re the matriarchal cells of the brain, from which spring all except one type of cell populating our most highly regarded (at least by itself) organ. They can remain in their primordial state for decades, languidly dividing just enough to replace their own numbers. Alternatively, they can spawn daughter cells that depart from the primordial state.

It’s the matriarchs’ daughters – so-called neural progenitor cells – that embark on committed differentiation pathways giving rise to nerve cells and other key brain cells. Given that lofty ambition, it’s not surprising that neural progenitor cells divide much more rapidly than their parents do, outnumbering neural stem cells probably by 1,000 to 1 or more.

It turns out that neural progenitors can do more than breed. They’re excellent managers, too. In a new Nature Neuroscience study that I describe in this news release, Stanford neuroscientist Tony Wyss-Coray, PhD, and his colleagues demonstrated that neural progenitor cells squirt out substances regulating the behavior of the one type of brain cell that doesn’t call them grandma.
  • Microglia normally are distributed throughout the brain – rather small, quiescent cells sprouting long, skinny projections that meekly but efficiently survey large areas that, taken together, cover the entire brain. But if this surveillance reveals signs of a disturbance, such as injury or infection, the microglia whirl into action. They begin proliferating and their puny bodies puff up, metamorphosing from mild-mannered Clark Kent-like reporters to buffed Supermen who fly to the scene of trouble, where they secrete substances that can throttle bad actors or call in reinforcements. Within these activated cells, internal garbage disposals called lysosomes form in large numbers and start whirring, ready to make mincemeat out of pathogens or cellular debris.

Wyss-Coray’s group showed, in rodents, that specific factors secreted by neural progenitor cells get microglia pumped. The discovery is significant considering that in the two places in the adult mammalian brain (including the human variety) where neural stem and progenitor cells reside, they’re typically closely associated with an entourage of microglia.

Now we know who’s boss. And we may have a clue about why stem-cell transplants seem to improve brain function, even though the stem cells don’t actually engraft very well.

Word List:
matriarchal: controlled by women rather than men; passing power, property, etc. from mother to daughter rather than from father to son
primordial: very basic
languid: moving slowly in an elegant manner, not needing energy or effort
to spawn: to cause something to develop or be produced
to embark on: to start to do something new or difficult
to give rise: to cause something to happen or exist
lofty: very high and impressive
to squirt: to force liquid, gas, etc. in a thin fast stream through a narrow opening; to be forced out of a narrow opening in this way
quiescent: quiet; not active; not developing, especially when this is probably only a temporary state
to sprout: to appear; to develop something, especially in large numbers; to start to grow something; to start to grow on somebody/something
to whirl: to move, or make somebody/something move, around quickly in a circle or in a particular direction
to proliferate: to increase rapidly in number or amount
puny: small and weak
to puff up: to swell or to make something swell
metamorphosis: a process in which somebody/something changes completely into something different
to secrete: to produce a liquid substance
to throttle somebody: to attack or kill somebody by squeezing their throat in order to stop them from breathing
garbage disposal: a machine connected to the waste pipe of a kitchen sink, for cutting food waste into small pieces
entourage: a group of people who travel with an important person
to engraft: to incorporate in a firm or permanent way; implant: