Newsgroup: italia.firenze.discussioni
Titolo: [INGLESE] Staminali etiche

Da Nature
'Ethical' routes to stem cells highlight political divide
Split opens over methods to create nonviable embryos.
Erika Check & Carina Dennis
Religious and ethical concerns are forcing researchers using human 
embryonic stem cells to seek ways to sidestep these issues. In a first 
attempt, biologists this week revealed details of two techniques for 
deriving the cells that do not involve the destruction of a viable embryo.
Both methods work in mice and, in principle, could be applied to human 
embryos. But scientists, ethicists and politicians are split over the 
merits of the two techniques.
Embryonic stem (ES) cells can develop into any tissue in the body, so 
have great potential for a range of therapies. And if they are cloned 
from a cell in the patient's body, the resulting cell line would 
genetically match that individual. This can be done using a technique 
dubbed 'therapeutic cloning', in which the nucleus from the donor cell 
is inserted into an egg stripped of its own genetic material. Earlier 
this year, researchers in South Korea became the first to use this 
method to derive human ES cells that genetically matched the patient 
(see Nature 435, 393; 2005).
But the ethical concerns inherent in destroying an embryo to create the 
cell lines are too much for some, especially religious groups, and many 
countries have restricted the research that can be done. In Germany, for 
example, the use of ES cell lines created since January 2002 is illegal 
and carries a penalty of up to three years in jail. And in the United 
States, federal funds for ES cell work is only available for a handful 
of cell lines derived before August 2001.
But there is currently heated debate on the issue in the US Senate, 
where lawmakers are considering loosening the restrictions. Some 
senators unhappy with those proposals have suggested that 'alternative' 
methods of deriving the cells, which don't requir e the destruction of 
viable embryos, could help to bridge the ethical divide (see Nature 436, 
309; 2005).
Until now, such methods have been purely theoretical, but in work 
published online by Nature this week, two teams report their successful 
use in mice. Rudolf Jaenisch and Alexander Meissner of the Massachusetts 
Institute of Technology describe a variant of therapeutic cloning called 
altered nuclear transfer (ANT), in which a gene in the patient's donated 
cell is switched off before the nucleus is transferred into a fertilized 
egg. The resulting egg grows into a normal ball of cells called a 
blastocyst from which ES cells can be derived, but the deactivated gene 
means that the ball lacks the ability to implant in a uterus and so 
develop into a baby (A. Meissner and R. Jaenisch Nature 
doi:10.1038/nature04257; 2005).
In the other paper, a team led by Robert Lanza of Advanced Cell 
Technology in Worcester, Massachusetts, plucked single cells called 
blastomeres from eight-cell embryos. They derived new ES cell lines from 
the blastomere, while the embryos went on to form apparently healthy 
mice (Y. Chung et al. Nature doi:10.1038/nature04277; 2005).
This method is similar to a technique used in in vitro fertilization 
(IVF) called preimplantation genetic diagnosis (PGD), in which a 
blastomere is removed from the eight-cell embryo for genetic tests 
before it is implanted. The work by Lanza's team raises the possibility 
that fresh stem-cell lines could be derived from human embryos being 
used in IVF before they are transferred to the uterus.
Although the quality of the work is impressive, there is much 
disagreement over the ethical benefits of each strategy. Some scientists 
seem more convinced by the PGD method.
In the balance
"In my mind, this takes away the ethical dilemma of destroying embryos," 
says Alan Trounson, a reproductive biologist at Monash University in 
Melbourne, Australia.
There is currently a moratorium on therapeutic cloning in Australia, due 
for review at the end of this year, and Trounson has applied to the 
country's major medical funding agency to do similar work with human PGD 
embryos.
But there is the practical disadvantage that the resulting cell lines 
can come only from the embryos of couples undergoing IVF, so wouldn't be 
genetically matched to patients. And ethicists are troubled by the 
question of whether the extracted blastomere itself has the potential 
for life. "If you grow it in certain conditions, it could divide and 
differentiate to have the same properties as embryos," explains Yuri 
Verlinsky, chief executive of the Reproductive Genetics Institute in 
Chicago.
Although the number of successful births from PGD embryos indicates that 
removing a single cell early on doesn't compromise the baby, it is still 
possible that it might have subtle long-term consequences. "You are 
getting a live birth, but are you getting the same child you would 
otherwise get?" asks William Hurlbut, a consulting professor at Stanford 
University and a prominent advocate of ANT. "It is uncomfortable to me 
to endorse such a strategy."
Because of this, Hurlbut says that the PGD method is unlikely to get 
past the Dickey Amendment, which is passed by the US Congress every year 
and forbids federal funds being spent on experiments that endanger or 
destroy an embryo. And President George W. Bush's Council on Bioethics, 
on which Hurlbut sits, dismissed the idea earlier this year in a white 
paper on alternative means for deriving ES cells.
The ANT method of altering the genetic make-up of an embryo troubles 
some scientists, but seems more acceptable to conservative ethicists and 
religious figures. "I think this is an artificial concept and I'm not 
comfortable with it," says Trounson. "You do an engineering step to 
essentially destroy the embryo so that you can then use it." Because of 
this, some argue that ANT might itself fall foul of the Dickey Amendment.
George Daley of Harvard Medical School in Boston is also unconvinced, 
partly because the effects of the genetic modification don't kick in 
until the eight-cell stage. "A normal embryo and the embryo created by 
this method are indistinguishable until that stage," he says.
But Hurlbut maintains that the altered embryo has no moral status. "You 
have the embryonic equivalent of brain death," he says. "This changes 
the dynamic of the political debate," agrees analyst Eric Cohen of the 
Ethics and Public Policy Center in Washington DC.
Hurlbut is doing all he can to push ANT, and has compiled a public 
letter supporting it signed by scientists, ethicists and religious 
figures. And in August 2004, he persuaded William Levada, one of the 
most prominent Catholics in the United States, to write to President 
Bush encouraging him to consider the method. The president's bioethics 
council also gave the idea tentative support in its white paper.
Some observers warn against overreacting to the work. "If science gets 
us to the point where we don't need embryos any more that's fine, but 
right now policy-makers are making a huge mistake if they say 'we've got 
one paper and we'll make policy based on that'," says Sean Tipton of the 
Coalition for the Advancement of Medical Research in Washington DC.
And either way, the ethical debate over what constitutes life ? or the 
potential for life ? looks set to dog the field. "The challenge is to 
define what an embryo is," says Hurlbut. "We need to sort that out or 
we'll be having this argument all the way along."
References
[1]Meissner A. Jaenisch R. . Nature advanced online publication doi: 
10.1038/nature04257 (2005).
[2] Chug Y. et al. Nature advanced online publication doi: 
10.1038/nature04277 (2005).
 
-- 
Life's but a walking shadow
a poor player that struts and frets his hour upon the stage
an then is heard no more
it is a tale told by an idiot full of sound and fury
signifying nothing.
 From the Scottish drama of Bill


A Ruini intanto non gli andra' bene manco cosi....Ora si schierera' dalla
parte dei poveri topini blhea che schifo
:\
Serena

 Ora si schierera' dalla parte dei poveri topini blhea che schifo :\ 
Ma no tanto sono clonati...
Ciao,
Alessandro


 Alessandro
In inglese non ero molto brava infatti non son riuscita a tradurlo benissimo
,sono un po' dura, e quindi la santissima chiesa a cosa si e' attacata se
non hai topini?
Scusami ma la cosa mi interessa molto da vicino e vorrei capire?!
Grazie :))
Serena

 Scusami ma la cosa mi interessa molto da vicino e vorrei capire?!
E' un discorso complesso. Queste sono le tecniche:
Fino ad adesso questi metodi [per ottenere cellule staminali (CS) senza 
distruggere l'embrione] sono stati puramente teorici, ma in un lavoro 
pubblicato online su Nature questa settimana due gruppi riportano il 
successo del loro uso nei topi. Rudolf Jaenisch e Alexander Meissner del 
Massachusetts Institute of Technology descrivono una variante della 
clonazione terapeutica chiamata Trasferimento Nucleare Alterato (TNA) in 
cui un gene della cellula donata dal paziente e' spento prima del 
trasferimento del nucleo in un ovulo fertilizzato. L'ovulo risultante 
cresce in un normale ammasso di cellule chiamato blastocisti da cui le 
CS possono essere estratte, ma il gene disattivato impedisce all'ammasso 
  l'impianto nell'utero e il successivo sviluppo in un feto (A. Meissner 
and R. Jaenisch Nature doi:10.1038/nature04257; 2005).
Nell'altro articolo, un gruppo guidato da Robert Lanza dell'Advanced 
Cell Technology in Worcester, Massachusetts, ha prelevato singole 
cellule chiamate blastomeri da embrioni di 8 cellule. Hanno poi derivato 
linee di CS dal blastomero mentre gli embrioni hanno proseguito il loro 
sviluppo per formare topi apparentemente sani (Y. Chung et al. Nature 
doi:10.1038/nature04277; 2005).
Questo metodo e' simile ad una tecnica usata nella fertilizzazione in 
vitro (FIV) chiamata diagnosi genetica preimpianto (DGP) in cui un 
blastomero e' rimosso da un embrione di 8 cellule per analisi genetiche 
prima dell'impianto. Il lavore del gruppo di Lanza solleva la 
possiblita' che linee fresche di CS possano essere derivate da embrioni 
umani usati nella FIV prima del loro trasferimento nell'utero.
Chi crede nel TNA (Hurlbut di Stanford) sostiene che potrebbero esserci 
conseguenze impreviste a lungo termine ("Dai vita ad un bambino, ma e'lo 
stesso bambino che avresti senza prelevare quella cellula?")
Il metodo TNA disturba alcuni scienziati, ma sembra essere piu' 
accettabile dai religiosi Trouson (a favore del DGP) dice "Fai un passo 
di ingegneria che distrugge l'ambrione cosicche' to possa utilizzarlo"
Traduco questa che e' una perla:
Hurlbut sta facendo tutto quello che puo' per spingere il TNA ed ha 
scritto una lettera aperta di sostegno ad esso firmata da scienziati, 
filosofi etici e figure religiose. Nell'Agosto 2004 ha persuaso W Levada 
uno dei cattolici piu' prominenti degli USA a scrivere al Presidente 
Bush incoraggiando la considerazione del metodo. Il comitato 
presidenziale di bioetica ha dato un appoggio preliminare al metodo nel 
suo libro bianco.
Ora la questione si riduce a questo
1) si preleva una cellula e gli si fa produrre CS. Ma se la cellula puo' 
generare un embrione non ha anche essa i diritti di un embrione? A parte 
le conseguenze a lungo termine
2) Uccidi la cellula clonata visto che l'embrione che si forma non puo' 
impiantarsi nell'utero.
Ce n'e' piu' che abbastanza per attaccarsi se uno vuole opporsi...


 Alessandro
Purtroppo si :|
Serena