The following excerpts are from ;
Science Magazine Online
June 8, 2001
It offers replies from the scientists to the arguments that adult stem
cell research is sufficient. It also responds to the media hype over the
use of fat cells and of cadavers as a source of stem cells, with the
facts about the reported research. And it explains the difference between
peer reviewed, published research results from NIH and university
sponsored studies and the non-reviewed results announced by commercial
firms --

The two main points of the article;
-- most scientists who work in the field agree that both embryo and adult
stem cell research are needed to eventually advance to clinical
applications and actually being able to cure diseases -- especially true
for neurological diseases.
-- these clinical applications are still years away.
 linda

 STEM CELL POLICY:
 Can Adult Stem Cells Suffice?
BY  Gretchen Vogel

' ... most scientists in the field--including those who work with
 adult-derived cells--caution that recent advances, although promising,
do
 not mean that adult cells can replace the need for those derived from
 embryos or fetal tissue. For some diseases, they say, adult cells may
 indeed turn out to be the better choice. But for other applications,
 embryo-derived cells have some distinct advantages. Scientists working
 mostly with ES cells derived from mice have found that they multiply
more
 readily in the lab than do their adult counterparts, providing as many
 cells as needed, and they seem far more proficient in producing certain
 specialized cell types, such as dopamine-producing neurons and
 insulin-producing cells. "It's incorrect to say that these published
 papers show that the adult cells are equivalent to embryonic stem cells
 for treating diabetes and Parkinson's," says Ron McKay of the National
 Institute of Neurological Disorders and Stroke (NINDS) in Bethesda,
 Maryland.

 Fat and Frankenstein
 Both types of cells could prove to be a tremendous boon to medicine.
 ...Eventually, scientists would like to use stem cells to replace
damaged or
 worn-out tissues--for instance, to treat paralyzing spinal cord
injuries.
 This might work if scientists can figure out how to guide the growth of
 stem cells--immature cells that can replicate themselves and give rise
to
 mature daughter cells. The stem cells themselves are found in many
 tissues in the body and also in developing embryos and fetuses. Those
 isolated from embryos are pluripotent--meaning that, with the correct
 cues, they can give rise to any kind of cell in the body. Stem cells in
 adult tissue are often multipotent--they can produce many, but not all,
 cell types.

...One recent paper captured the public's imagination as few others have.
In
 the April issue of Tissue Engineering, surgeon Marc Hedrick of the
 University of California, Los Angeles, and his colleagues reported that
 fat cells isolated after liposuction could become cells resembling
 cartilage, bone, and muscle. The paper has prompted numerous sound
bites,
 with several politicians volunteering to give up some of their fat to
 further research. But although the image of liposuction as an altruistic
 operation might be attractive, developmental biologist Douglas Melton of
 Harvard University says the study leaves several key questions
 unanswered. He speculates, for instance, that the team may have cultured
 a circulating hematopoietic stem cell, rather than a fat cell. That may
 be so, says co-author Adam Katz of the University of Pittsburgh, but he
 suspects people will prefer liposuction to bone marrow donation any day.

 Cell biologist Bruce Spiegelman of the Dana-Farber Cancer Institute in
 Boston is similarly circumspect. He points out that the four cell types
 the team described--fat, cartilage, muscle, and bone--are all part of
the
 mesenchymal cell family and have already been derived from several stem
 cell sources. The paper reports no sign that the cells could become
nerve
 cells or the much-sought-after pancreatic cells. Fat cells might be
 abundant, Spiegelman says, but "they are a far cry from being the answer
 to everything we need."

 The next paper to make a major splash described isolating stem cells
from
 cadavers. "Frankenstein cells," several headlines proclaimed. As
 described in the 3 May issue of Nature, neuroscientist Fred Gage of the
 Salk Institute for Biological Studies in La Jolla, California, and his
 colleagues cultured neural progenitor cells from brain tissue taken from
 cadavers shortly after death. Gage notes that the team members were
 careful to call their cells neural "progenitors" instead of neural "stem
 cells." The cells could divide and differentiate in culture, but the
team
 didn't show that they could both replicate themselves and produce mature
 daughter cells--the true test of a bona fide stem cell. The cells also
 had a limited lifetime in culture--a major disadvantage for scientists
 trying to coax cells to become a particular tissue type. In short, says
 Gage, the technique is a long way from clinical application.

 At least two companies have announced--but not published--that they have
 identified or produced pluripotent cells without using embryos or fetal
 tissue. Although the claims got plenty of play in the press, most stem
 cell scientists are dubious. In April, a company called Anthrogenesis,
 located in Cedar Knolls, New Jersey, announced via a telephone press
 conference that it had isolated stem cells from human placentas that
 might be the equivalent of human pluripotent stem cells. These placental
 cells can differentiate into nerves and blood vessels, the company says,
 although chief scientific officer Robert Hariri says they are still
 characterizing the cells. "These claims ... were just absolutely
absurd,"
 says John Gearhart of Johns Hopkins University, who isolated pluripotent
 stem cells from fetal tissue in late 1998. "If you don't have published
 research reports, how are [colleagues] supposed to judge a claim?"
Hariri
 says the company has submitted several papers describing the cells,
 although none have been published yet.

... Strong signs from bones
 In one tissue, at least, scientists agree that the results are
 encouraging. In the past few months, a series of papers has strengthened
 the idea that cells in the bone marrow can respond to cues from damaged
 tissue and help repair it. Until recently, doctors had only attempted to
 use bone marrow stem cells to reconstitute the blood or immune system.

 But late last year, two teams reported that mouse cells derived from
bone
 marrow could become neuronlike cells (Science, 1 December 2000, pp. 1775
 and 1779). In April, another two groups reported that bone
marrow-derived
 cells could help repair damaged heart muscle. In one study, Piero
Anversa
 of New York Medical College in Valhalla and Donald Orlic of the National

 Perhaps most impressive, in the 4 May issue of Cell, scientists reported
 that a single cell from the bone marrow of an adult mouse can multiply
 and contribute to the lung tissue, liver, intestine, and skin of
 experimental mice. Researchers knew that a tiny subset of cells purified
 from bone marrow had the potential to multiply and give rise to all the
 blood cell types, but isolating those cells has been very difficult. To
 increase their chances of capturing the elusive cells, Diane Krause of
 Yale University School of Medicine and Neil Theise of New York
University
 Medical School and their colleagues performed a double bone marrow
 transplant. They first injected bone marrow cells from a male mouse,
 tagged with green fluorescent protein, into the bloodstream of female
 mice that had received a lethal dose of radiation. Two days later, they
 killed the recipient mice and isolated a handful of green-tagged cells
 that had taken up residence in the bone marrow. (Previous studies had
 suggested that the most primitive transplanted cells lodge in bone
 marrow.) They then injected irradiated mice with just one of the
 green-tagged cells accompanied by untagged, female-derived bone marrow
 cells that survive about a month. When the scientists killed the
 surviving mice 11 months after the second transplant, they found progeny
 from the cells in lung, skin, intestine, and liver as well as bone and
 blood. "Bone marrow stem cells can probably form any cell type," says
 Harvard's Melton.

 Even so, Krause says her work highlights the need for more work on ES
 cells rather than suggesting a replacement: "We basically have a black
 box. We put the cells in at the beginning and look at the mice" several
 months later. Because only six of the 30 mice that received a
single-cell
 transplant survived, Krause estimates that one-fifth of cells harvested
 from the first transplant recipients have such broad potential. The
 scientists don't know why the most versatile cells go to the bone marrow
 in the first transplant, nor can they predict which ones might have the
 potential to multiply and differentiate.

 Melton also notes that cells from bone marrow have one major drawback:
 Although they are fairly easy to collect from donors, the cells do not
 grow well outside the body--and not for lack of trying. "Biotech
 companies have spent tens of millions of dollars on that problem,"
Melton
 says. "I don't think it's going to happen very easily."

 ... Two are better than one
 Most researchers say they need access to both embryonic and adult stem
 cells. McKay points out that embryonic cells have one huge advantage
over
 adult-derived cells: their ability to divide in culture. "The ES cell
 will be the basis for how you will get large numbers of cells," he says.
 Gearhart of Johns Hopkins adds that the ability of embryonic and fetal
 cells to divide in the lab makes them a vital tool for learning how
 differentiating cells behave. "Answers to the problems of how you would
 do things with adult stem cells will probably come from the embryonic
and
 fetal cells," he says. "There's no other way you're going to get that
 information."

 But ES cells have plenty of limitations, too. For one, murine ES cells
 have a disturbing ability to form tumors, and researchers aren't yet
sure
 how to counteract that. And so far reports of pure cell populations
 derived from either human or mouse ES cells are few and far
 between--fewer than those from adult cells.

 Even if adult-derived cells do become the favorite for some treatments,
 such applications are years away, says McKay. The long-term consequences
 of stem cell therapies are completely unknown, as few animal studies
have
 looked at results longer than a year after transplants. And scientists
 need to know more about the process of cell differentiation before
anyone
 will be able to tell which cells hold the most hope for curing disease,
 McKay notes. "All of these cells," he says, "are partial solutions for
 the moment."

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