The Scientist 14[23]:20, Nov. 27, 2000
http://www.thescientist.com/yr2000/nov/research_001127.html

Blood
Goal: To develop a limitless source of blood cells for transfusions.

Over the past 30 years, a small army of researchers has investigated the
culture conditions under which hematopoietic ASCs preferentially give rise
to myeloid or lymphoid lineages. (Relatively pure cultures of red blood cells
have been the most elusive to produce.) Gordon Keller, a professor at
Mount Sinai School of Medicine's Institute for Gene Therapy and
Molecular Medicine, has succeeded at differentiating mouse ESCs
into a variety of blood cell types, though he admits that generating
lymphocytes is still a problem. His lab has developed the requisite
protocols by trial and error over the past decade.19

When removed from conditions that keep them in an undifferentiated
state, ESCs form clusters of differentiating cells called embryoid bodies.
"At that point, we take the cells from the embryoid body and put them
into cultures containing cytokines that stimulate the growth and
maturation of blood-cell progenitors," Keller recounts. "Alternatively,
we can first isolate the blood-cell progenitors from the embryoid
bodies by using antibodies to specific cell-surface markers and then
put them into culture."

Keller is now searching within embryoid bodies for the hematopoietic
stem cell equivalent to the hematopoietic ASC that other labs have
isolated in bone marrow. This putative stem cell in the embryoid body
has been harder to find, he says, because it "appears to be more immature
than the one in adult bone marrow." His approach is to transplant
candidate stem cells into mice with drug-damaged hematopoietic systems
and then to observe whether blood-cell re-population occurs. When
might his methods boost human blood supplies for transfusions?
"Some years away" is all that Keller will predict.
 
Douglas Steinberg is a freelance writer in New York.

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