Now researchers at the New York stem cell Foundation, the laboratory developed a method that can help to recover lost ground.
Embryonic stem cells can generate all the tissues of the body. So if these cells can be developed from the cells of adult patient, it may be possible to make replacement cells for every patient tissue without fear of rejection.
At first it seemed that stem cells can be made of implantation of the nuclei of adult patient in an unfertilized human egg, or oocyte, whose nucleus has been removed. Mysterious factors in the body of the egg to adult cells to lose its specialist nature and back in its infancy where all fate open to him.
However, this method is highly inefficient and will require dozens or hundreds of eggs for each patient. A major step forward was made in 2007, when Shinya Yamanaka found a way to avoid using human eggs.
He guessed oocyte reprograms the inserted nucleus and showed that by injecting protein factors in only four cells of the adult patient, he could make it back to an embryonic State. Cells made by Dr. Yamanaka, called induced pluripotent stem cells, or iPS cells. At first it seemed they are identical as hoped, embryonic cells made using the oocytes.
But as researchers examine them more closely, they found more and more anomalies, making the cells unsuitable for therapeutic use. In particular, iPS cells seem to preserve the memory, in the form of chemical signals in the material, which drives their DNA, their previous personality. This trace memory to prevent them from morphing into other types of cells when needed.
The team led by Scott Noggle and Dieter Egli, New York stem cell Foundation, now back to the basics, trying to improve on an original method of using eggs to create patient-derived embryonic stem cells.
Happy coincidence, as part of the management of the experiment they left the egg nucleus in place when they implanted the adult nucleus. They noticed that in the presence of a nucleus of ova, embryos from adult cell nucleus inserted developed much further than usual. They progressed, in fact, the blastocyst stage, the point at which embryonic stem cells can be collected, researchers report in Wednesday's issue of nature.
With several species including mice and cow cells to easily reach the blastocyst stage, and from there a donor you can clone when the blastocyst is implanted in the uterus. But despite all the worry about the cloning of people, in fact, it was nearly impossible to coax human eggs with the implanted nucleus to move to the stage of blastocysts. New York researchers say that they have not been able to repeat a claim that has been published.
Blastocysts, produced by New York triploidnyj, means that they have a normal diploid genome, or double inserted adults cells plus one oocyte genome. Triploidnyj cells are unstable and potentially cancerous and can never be put into patients. In addition, this process is too inefficient for therapeutic use is 63 oocytes were required to create a single normal set of embryonic cells.
"These cells are not therapeutically appropriate at this time," Dr. Noggle said.
Their relevance for research to study the process of the development of the blastocyst, and in particular to examine why the iPS cells is made by Dr. Yamanaka is reprogrammed. It may be that in addition to the four identified Dr. Yamanaka requires other factors. If these were to be identified, iPS cells can be put back on track as a starting point for therapy. Will remain the many difficult steps, like ensuring that the cells, which are created to restore the patient's tissues are programmed correctly, well behaved and benign.
Dr. Noggle and Dr. Egli also hope to adapt their way of getting useful blastocysts, the patient received. If the core of the human egg too early, it probably does not provide enough of the factors necessary to reprogram the nucleus. If it is after the first cell division, it merges with the inserted nucleus and can not be removed. You may be able to yank it at the last possible minute, when he made enough reprogramming job, and get a normal diploid blastocysts are formed from cells of the patient.
Research stands as a stepping stone to success, "Dr. George q. Daley, a stem cell expert at children's Hospital Boston, writes in a commentary in nature. He also calls "the provocative question," he said, of whether the patient received embryonic cells, made the old-fashioned way with ova can work better than the iPS cells.
Researchers from the New York stem cell Foundation, has the advantage of access to abundant oocytes because they worked with Columbia University program, which pays donors $ 8000. Many ethicists fear that payments to donors will lead to a market in organs, and they hoped that enough oocytes will be donated for free. The National Academy of Sciences has published guidelines for stem cell research, saying that donors should not be paid.
But oocyte donation is a difficult process, and stem cell researchers in many countries have been unable to find enough volunteers for their experiments to proceed. Starting in 2009, the State of New York has allowed donors to receive reasonable compensation for eggs donated for stem cell research.