Re: [asa] Embryonic Stem Cells in Mice with No Embryos and No Cloning

From: Thomas Robey <>
Date: Thu Jun 07 2007 - 15:25:26 EDT


Seeing as I am still new to this list, but that the
stem cell topic happened to surface concurrently with
my arrival, I hope you are willing to follow a link to
what I think about the new reports.
or for now, just:

The one-sentence summary that I (as a scientist who
works with human embryonic stem cells) can offer is a
quote by Rudy Jaenisch indicating his perspective on
when this will be used in humans.

"This is really dangerous. We would never transplant
these into a patient." In his view, research into
embryonic stem cells made by cloning remains
"absolutely essential."



--- Rich Blinne <> wrote:

> Simple switch turns cells embryonic
> Technique removes need for eggs or embryos.
> David Cyranoski
> Research reported this week by three different
> groups shows that
> normal skin cells can be reprogrammed to an
> embryonic state in mice.
> The race is now on to apply the surprisingly
> straightforward procedure
> to human cells.
> If researchers succeed, it will make it relatively
> easy to produce
> cells that seem indistinguishable from embryonic
> stem cells, and that
> are genetically matched to individual patients.
> There are limits to
> how useful and safe these would be for therapeutic
> use in the near
> term, but they should quickly prove a boon in the
> lab.
> "It would change the way we see things quite
> dramatically," says Alan
> Trounson of Monash University in Victoria,
> Australia. Trounson wasn't
> involved in the new work but says he plans to start
> using the
> technique "tomorrow". "I can think of a dozen
> experiments right now —
> and they're all good ones," he says.
> In theory, embryonic stem cells can propagate
> themselves indefinitely
> and are able to become any type of cell in the body.
> But so far, the
> only way to obtain embryonic stem cells involves
> destroying an embryo,
> and to get a genetic match for a patient would mean,
> in effect,
> cloning that person — all of which raise difficult
> ethical questions.
> As well as having potential ethical difficulties,
> the 'cloning'
> procedure is technically difficult. It involves
> obtaining unfertilized
> eggs, replacing their genetic material with that
> from an adult cell
> and then forcing the cell to divide to create an
> early-stage embryo,
> from which the stem cells can be harvested. Those
> barriers may have
> now been broken down.
> "Neither eggs nor embryos are necessary. I've never
> worked with
> either," says Shinya Yamanaka of Kyoto University,
> who has pioneered
> the new technique.
> Last year, Yamanaka introduced a system that uses
> mouse fibroblasts, a
> common cell type that can easily be harvested from
> skin, instead of
> eggs. Four genes, which code for four specific
> proteins known as
> transcription factors, are transferred into the
> cells using
> retroviruses. The proteins trigger the expression of
> other genes that
> lead the cells to become pluripotent, meaning that
> they could
> potentially become any of the body's cells. Yamanaka
> calls them
> induced pluripotent stem cells (iPS cells). "It's
> easy. There's no
> trick, no magic," says Yamanaka.
> The results were met with amazement, along with a
> good dose of
> scepticism. Four factors seemed too simple. And
> although the cells had
> some characteristics of embryonic cells — they
> formed colonies, could
> propagate continuously and could form cancerous
> growths called
> teratomas — they lacked others. Introduction of iPS
> cells into a
> developing embryo, for example, did not produce a
> 'chimaera' — a mouse
> carrying a mix of DNA from both the original embryo
> and the iPS cells
> throughout its body. "I was not comfortable with the
> term
> 'pluripotent' last year," says Hans Schöler, a
> stem-cell specialist at
> the Max Planck Institute for Molecular Biomedicine
> in Münster who is
> not involved with any of the three articles.
> This week, Yamanaka presents a second generation of
> iPS cells, which
> pass all these tests. In addition, a group led by
> Rudolf Jaenisch at
> the Whitehead Institute for Biomedical Research in
> Cambridge,
> Massachusetts, and a collaborative effort between
> Konrad Hochedlinger
> of the Harvard Stem Cell Institute and Kathrin Plath
> of the University
> of California, Los Angeles, used the same four
> factors and got
> strikingly similar results.
> "It's a relief as some people questioned our
> results, especially after
> the Hwang scandal," says Yamanaka, referring to the
> irreproducible
> cloning work of Woo Suk Hwang, which turned out to
> be fraudulent.
> Schöler agrees: "Now we can be confident that this
> is something worth
> building on."
> The improvement over last year's results was simple.
> The four
> transcription factors used by Yamanaka reprogramme
> cells
> inconsistently and inefficiently, so that less than
> 0.1% of the
> million cells in a simple skin biopsy will be fully
> reprogrammed. The
> difficulty is isolating those in which reprogramming
> has been
> successful. Researchers do this by inserting a gene
> for antibiotic
> resistance that is activated only when proteins
> characteristic of stem
> cells are expressed. The cells can then be doused
> with antibiotics,
> killing off the failures.
> The protein Yamanaka used as a marker for stem cells
> last year was not
> terribly good at identifying reprogrammed cells.
> This time, all three
> groups used two other protein markers — Nanog and
> Oct — to great
> effect. All three groups were able to produce
> chimaeric mice using iPS
> cells isolated in this way; and the mice passed iPS
> DNA on to their
> offspring.
> Jaenisch also used a special embryo to produce
> fetuses whose cells
> were derived entirely from iPS cells. "Only the best
> embryonic stem
> cells can do this," he says.
> "It's unbelievable, just amazing," says Schöler, who
> heard Jaenisch
> present his results at a meeting on 31 May in
> Bavaria. "For me it's
> like Dolly [the first cloned mammal]. It's that type
> of
> accomplishment."
> The method is inviting. Whereas cloning with humans
> was limited by the
> number of available eggs and by a tricky technique
> that takes some six
> months to master, Yamanaka's method can use the most
> basic cells and
> can be accomplished with simple lab techniques.
> But applying the method to human cells has yet to be
> successful. "We
> are working very hard — day and night," says
> Yamanaka. It will
> probably require more transcription factors, he
> adds.
> If it works, researchers could produce iPS cells
> from patients with
> conditions such as Parkinson's disease or diabetes
> and observe the
> molecular changes in the cells as they develop. This
> 'disease in a
> dish' would offer the chance to see how different
> environmental
> factors contribute to the condition, and to test the
> ability of drugs
> to check disease progression.
> But the iPS cells aren't perfect, and could not be
> used
=== message truncated ===

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Received on Thu Jun 7 15:25:52 2007

This archive was generated by hypermail 2.1.8 : Thu Jun 07 2007 - 15:25:52 EDT