- The Washington Times - Wednesday, March 15, 2000

Pigs have been cloned for the first time, dramatically changing the world of medicine.

The scientists who engineered the births of the five piglets, now 10 days old, said yesterday their success means it soon will be possible to produce genetically engineered pigs whose kidneys, hearts, livers and other organs could be transplanted into humans without fear of rejection.

What's more, genetically engineered cloned pigs will provide a source of stem cells for developing "cell-based therapies neurons for treatment of Parkinson's and Alzheimer's diseases, for instance, and pancreatic cells that produce insulin for treatment of diabetes, skin cells for burn victims, and the rest," said David Ayares.

Mr. Ayares is the head of research and development at the U.S. division of PPL Therapeutics in Blacksburg, Va. It was his team that created the porcine clones. PPL Therapeutics is the Edinburgh, Scotland-based research firm that in a joint venture with Edinburgh's Roslin Institute produced Dolly, the first cloned sheep, three years ago.

The cloning is important because pig organs are similar to human organs. Heart valves of pigs already are used to replace damaged valves in humans. And scientists around the world have for several years been studying pigs as potential sources for other transplant organs.

If, in fact, pig organs can be used in humans without fear of rejection the worldwide shortage of transplant organs will end. Countless lives will be saved.

Ron James, managing director of PPL Therapeutics said: "An end to the chronic organ shortage is now in sight. All the known technical hurdles have now been overcome."

And Mr. Ayares said in a phone interview that he is now "certain" that is so. He added that "with the techniques we have developed, we can modify pigs in a very precise way, removing certain genes such that hearts and kidneys from these animals can be transplanted into humans without fear of rejection."

The PPL scientist said: "We can do genetic modification of pig cells. We have done it. We know we can do it. We've 'knocked out' the genes in the cells that cause human rejection."

The next step is to genetically engineer cells that form embryos for transplantation into surrogate mothers and thus produce genetically altered pigs. Mr. Ayares predicts clinical trials in humans will come in about four years.

In a statement to the Associated Press, Dr. Fritz Bach of the Harvard Medical School, a specialist in genetic and immunological transplants, said: "I think this is a big step forward they've made. I applaud it."

Dr. Bach added, however, that there may be ethical issues to overcome regarding animal-to-human transplants. He said there is a risk of introducing to humans germs that are common to the animals but not to humans.

Princeton University microbiologist Lee Silver, a renowned cloning specialist, said "the transition of diseases is a technical problem, and it can probably be overcome." If so, "there is no ethical problem involved."

Nonetheless, Mr. Silver said he suspects some will rebel at the idea of growing genetically engineered pigs for their organs. He said, though, that there is no ethical problem there either. "If people grow and eat pigs, they should be willing to use them as a source of organs to save human lives," he argues.

Likewise, the use of engineered pig cells for stem-cell research is likely to take fire from the debate over use of donated human fetuses for such experimentation.

Researchers can use the pigs to "harvest organs or harvest cell types. This changes the whole dialogue. The use of pig cells provides a parallel strategy an alternative for researching cell mediated therapies," Mr. Ayares said.

He concedes there may be special reasons to harvest human cells. And Tim Leshan of the American Society for Cell Biology concurs. He said it would be "nice" if the feuding over the use of fetal cells were over, but he suspects it is "too early" to predict that.

An intense battle has erupted over harvesting stem cells from fetuses because many believe human life begins at conception. They say a fetus is, in fact, equivalent to an adult. Killing a cell mass even at the earliest fetal stage and even in a quest to find remedies for currently incurable diseases is murder.

Scientists tend to regard cell masses in the earliest stages of fetal development as worthy of special respect, but not as human beings. Beyond that, they argue that the donated fetuses they wish to use are leftovers from fertility clinics and are destined for destruction anyway.

The pig fetuses the PPL Therapeutics researchers used came from various donor pigs.

The cells were harvested using so-called "nuclear transfer." Put simply, that means the part of a microscopically small cell housing chromosomes and genes the nucleus is taken from an egg cell and delicately transplanted into another egg cell from which the nucleus was removed.

The two cells then are immersed in special nurturing fluids where they fuse, eventually start dividing without normal fertilization, and grow into a cloned fetus.

The cloned pig fetuses were implanted into a sow named Destiny. She was expected to bear four clones, but she did the scientists one better. The offspring have been named Millie (because she was the first born in the "new millennium"), Christa (after Dr. Christian Barnard, the first to perform a heart transplant), Alexis and Carrel (after Nobel Prize winner Dr. Alexis Carrel), and Dotcom (because dot-com companies seem to be stock market high fliers).

• This article is based in part on wire service reports.

LOAD COMMENTS ()

 

Click to Read More

Click to Hide