Tailor-Made Stem Cells
Move Step Nearer Reality
Monkey Embryos Cloned
By Scientists in Oregon;
Medical Goal Is Distant
By GAUTAM NAIK
November 15, 2007; Page D4
The elusive quest to create tailor-made stem cells for use in treating human disease is a small but significant step toward realization, as scientists in Oregon created embryonic clones of monkeys and derived viable stem-cell lines from them.
A team led by Shoukhrat Mitalipov of the Oregon National Primate Research Center said that it had created monkey clones by using a variation of the process that yielded Dolly the sheep, the first cloned mammal.
Scientists have since cloned cows, cats, dogs, mice and other species, but never a monkey — a far closer evolutionary cousin to humans.
The experiments on rhesus macaque monkeys were first presented to a scientific meeting in Australia earlier this year. However, the research at the time hadn’t been assessed by other stem-cell experts. Yesterday, the data were published on the Web site of the peer-reviewed journal Nature. A separate paper by independent scientists experimentally validated the cloning work.
Dr. Mitalipov says that he now hopes to do two other ambitious experiments. The first is to take a rhesus embryonic clone to full term and thereby create the world’s first cloned monkey.
More usefully, perhaps, his team wants to test whether fresh tissue derived from rhesus clones can treat diabetes or other diseases in a monkey, a process known as therapeutic cloning.
Success in the second experiment — which is by no means assured — could strengthen the scientific rationale for conducting similar tests in human patients. The idea is to create an embryonic clone of a patient, then transplant altered versions of that embryo’s cells back into the patient.
Because the DNA of the transplanted tissue would match the DNA of the patient, the immune system likely wouldn’t reject it. Dr. Mitalipov and his research colleagues have prepared the groundwork for such experiments in monkeys.
In their lab, they injected the genetic material from a skin cell of an adult monkey into a monkey egg whose own DNA had first been removed.
This led to an early-stage embryo, called a blastocyst, from which stem cells were then derived. Finally, they put the stem cells in a petri dish and coaxed them into becoming long, thin nerve cells and beating heart tissue.
The technique is far from perfect, however. Although the team generated two embryonic stem-cell lines, one of them had genetic abnormalities.
The researchers also used more than 300 eggs from 14 rhesus monkeys to derive their cell lines — a highly wasteful process.
“It’s not ready to be a cost-effective option in humans,” because human eggs are harder to come by, Dr. Mitalipov said in a conference call with journalists.
Therapeutic cloning in people is a subject of ethical concern because early-stage clones, which some people consider to be living beings, are destroyed when stem cells are extracted from them.
Also, worries have been raised that the technique could be abused by renegade scientists who want to create fully developed human clones.
The field is under a cloud for other reasons.
In 2005, Korean researcher Hwang Woo Suk created a stir by publishing a paper in Science claiming that his team had extracted material from cloned human embryos that identically matched the DNA of 11 patients. Those results were later shown to be fabricated, and the paper was retracted.