http://www.the-scientist.com/yr2002/jan/defrancesco_p28_020107.html
Jan. 7, 2002
Two reports in the December issue
of Nature Biotechnology show that the potential of human embryonic stem
cells is being realized.1,2 One group led by S.C. Zheung at the University
of Wisconsin, Madison, and another led by B.E. Reubinoff from Hadassah
University, Jerusalem, have isolated highly purified populations of neuronal
progenitor cells from human embryonic stem cell (ESC) cultures.
These papers demonstrate that human
ESC cultures can be enriched for a single and specific progenitor cell
type. Furthermore, the cells, which by all measures appear to be neuronal
progenitor cells, behave this way in vitro and in vivo, and give rise to
the major cell types of the central nervous system (CNS).
The two groups used different schemes,
but their outcomes were remarkably similar. They first induced ESCs to
become neuronal progenitor cells and identified them by certain morphological
features. In the Zheung paper, neural, tube-like structures formed after
the cultures were grown for a few weeks in FGF-2-containing media. Reubinoff
simply starved the cultures, which caused ESCs to clump into little islands
of differentiating cells. Each group isolated the neuronal progenitor cells
away from the non-neuronal cells and treated them with various factors
to send them down the neuronal cell pathway. In culture, the cells turned
into the three major CNS cell types, some even showing signs of neurotransmitter
synthesis. After transplanting the neuronal precursor cells into mouse
brains, both groups found human cells in numerous brain regions, where
they appeared to have responded to host cues, as they differentiated into
neuronal cells and migrated along established pathways.
In addition to pure cultures of nerve
cells having obvious therapeutic uses, these cultures will provide a platform
for studying brain development. Zheung says, "When you compare what we
know about human brain development, in terms of time and landmarks, everything
is there in the dish. Critical structures in neuroendothelial cells are
almost identical to what we see in embryos."
Zheung and Reubinoff are certain
that the non-neuronal cells, which represent only a few percent of the
total, are differentiated ESCs, because they don't react with an ESC-specific
marker. This would pose the greatest threat, but neither can say for sure
what they are. Undifferentiated cells produce teratomas, so had they reacted
with the ESC marker, it would be problematic.
Laura DeFrancesco is a freelance
writer in Pasadena, Calif.
References
1. S.C. Zhang et al., "In vitro differentiation
of transplantable neural precursors from human embryonic stem cells," Nature
Biotechnology, 19:1129-33, December 2001.
2. B.E. Reubinoff et al., "Neural
progenitors from human embryonic stem cells," Nature Biotechnology, 19:1134-40,
December 2001.
The Scientist 16[1]:28, Jan. 7, 2002
The Scientist 16[1]:28
By Laura DeFrancesco
© Copyright 2002, The Scientist,
Inc