FRIDAY, March 7 (HealthDay News) -- Blood stem cells, which
later differentiate into all types of blood cells, originate and
are nurtured in the placenta, a U.S. study finds.
This finding may help researchers replicate the specific
embryonic microenvironment necessary to grow blood stem cells in
the lab so doctors can treat patients with diseases such as
leukemia and aplastic anemia, said senior author Dr. Hanna Mikkola,
a researcher in the Eli and Edythe Broad Center of Regenerative
Medicine and Stem Cell Research at the University of California,
Los Angeles (UCLA).
"It was a big mystery, where these cells originated. This is the
first time we can really say definitively that blood stem cells are
generated in the placenta. There's no more speculation," Mikkola
said in a prepared statement.
The discovery, reported in the March 6 issue of
Cell Stem Cell, was made in research with mice. The
researchers are now working to replicate it in humans.
"If we want to fully harness the potential of embryonic stem
cells to treat disease, it's critical for us to learn how to make
tissue-specific stem cells. We can learn that by studying what
happens during embryonic development," said Mikkola, an assistant
professor of molecular, cell and developmental biology and a
researcher at UCLA's Jonsson Comprehensive Cancer Center.
In previous research, Mikkola and her colleagues found the
placenta contained a large supply of stem cells, but the
researchers weren't sure if these stem cells were created in the
placenta or originated elsewhere and migrated to the placenta to
self-renew.
In this new study, Mikkola's team examined a unique mouse model,
a mouse embryo without a heartbeat. Because there was no blood
circulation, the researchers were able to find the blood stem cells
at their point of origin in the placenta.
"Using this model, we identified that the placenta has the
potential to make hematopoietic [blood] stem cells with full
differentiation ability to create all the major lineages of blood
cells. The placenta acts as a sort of kindergarten for these newly
made blood stem cells, giving them the first education they need,"
Mikkola explained.
More information
The National Institutes of Health has more about
stem
cells.
