A new type of hybrid cell created at Harvard University couldeventually solve the mystery of how embryonic stem cells develop intospecialized adult cells, and provide genetically tailored treatmentsfor many human diseases.
What's more, the technique holds out the possibility of doing this without creating or destroying human embryos.
The researchers fused adult skin cells with embryonic stem cells insuch a way that the genes of the embryonic cells reset the geneticclock of the adult cells, turning them back to their embryonic form.
Such adult-cum-embryo cells, taken from people with juvenilediabetes, Parkinson's, Alzheimer's, and other genetic diseases, couldreveal how such diseases develop and provide novel treatment for them.For example, normal cells might be made to replace abnormal ones thatcause juvenile diabetes and Alzheimer's disease. It should be possibleto coax these newly created embryonic cells "into replacement cells andeven organs," says biologist Chad Cowan who participated in theexperiments. "But it would definitely not be possible to clone theperson from which the adult cell came."
These potentials are not just around the corner. "We feel this is animportant achievement," notes Cowan. "We're very excited about it. Butwe have many technical hurdles to overcome before we're ready for theshowroom floor, before we can wheel out the prototype model."
Although the fusion method is more efficient and it satisfies manyethical concerns, he continues, "the achievement does not mean ongoingresearch using embryonic stem cells should be stopped or even slowed.Our technique may complement that of using these embryonic stem cells —even replace it some day — but that day is a long way off."
Cowan is the lead author of a report of the research published inthe August 26 issue of Science. The other authors are Kevin Eggan,Douglas Melton, and Jocelyn Atienza of the Harvard Stem Cell Institute.
Overcoming the hurdles
The next step is to puzzle out how an embryonic cell can turn back,or reprogram, the genes of an adult cell. That could take 10 years,Cowan guesses. "But is will eventually happen, and it will meanscratching at some of biology's fundamental questions in the process,"he says.
However, this long-term scratching at the fundamentals does not haveto delay the use of hybrid cells for helping patients. The quickest wayto new treatments, the researchers believe, is finding a way to removethe embryonic DNA. "That's the primary hurdle in the foot race to findtreatments for patients, " Eggan states.
The hybrid cells contain two sets of DNA, or genes, one from thereprogrammed adult cell and one from the embryonic "starter" cell. Totrack disease development, experimenters need to excise the latter.That done, they can determine how the adult cells differentiate intodiseased cells and tissues.
"This seems like the simplest and fastest approach," Cowan comments,"but my experience in biology is that the simplest things sometimesturn out to be the most difficult." This is why none of the researcherswill venture a guess on when it could happen, and why they adviseagainst any slowdown in research that requires embryos to be created ordestroyed.
The Harvard group obtained the starter cells by growing embryos fromexcess fertilized cells acquired from fertilization clinics with theowners' permission. Using such materials, Douglas Melton, the ThomasDudley Cabot Professor of the Natural Sciences in the Faculty of Artsand Sciences and co-director of the Harvard Stem Cell Institute, hascreated at least 17 new lines of embryonic stem cells using privatefunds (see March 4, 2004 Gazette). These are not part of the cell lineseligible for federal funding.
The new work on hybrids was done using stem cells made by Melton,then some of the experiments were repeated with a federally approvedline of cells. The adult cells came from foreskin and pelvic areas.
When all the problems are solved, the Harvard team sees a new sourceof stem cells produced without the need to create or destroy embryosthat some people insist are "alive." "We will never satisfy all of theethical objections to using embryonic stems cells," Cowan admits, "butwe believe that the majority of people will find this technique morallyacceptable. "
Cite This Page: