This story marks the first time I've had to use a pseudynm to protect the identity of a horse.

"Disney's" owner's desire for privacy only underscores the stakes here. Performance horses at his level can be worth $60,000 and more. Training, too, is an enormous investment. "Gretchen," as we call her in the piece, has spent years training Disney in English dressage (which, incidentally, makes for some very entertaining YouTube viewing if you have some time to kill). And so when she noticed that her horse's gait had started to suffer, she jumped to find a treatment.

Speed is key here, it was explained to me, because the smaller the injury, the better a horse's chance for recovery. Emphasizing that point is one of the main reasons Gretchen agreed to take part in this program. She says too many owners treat their horses' injuries with ever-greater doses of painkillers, delaying real treatment until it's too late. Gretchen estimated that, including all the preliminary visits and tests, Disney's treatment may reach $7,000.

Davis vets couldn't provide statistics on whether this treatment – injecting a horse's mesenchymal stem cells, drawn from the marrow of the animal's sternum, into the same animal's torn tendon – succeeds in producing new tendon tissue. (Part of the problem is that it's hard to distinguish tendon tissue from scar tissue, seen through an ultrasound.) But if it works, they believe humans may one day have another option for treating our torn ligaments, too.

Listen to the Stem Cells and Horses radio report online, and watch our Web Extra Slideshow.

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Identical twins are more similar to one another than a clone
will be to the person cloned.

Of course, these cells aren't any less controversial than they were eight years ago. Researchers will still need to destroy embryos to get these cells (at least until they perfect iPS cells which would make this part of the debate moot). Anyone who considers an embryo made up of a few hundred cells to be alive will protest that embryo's destruction.

This is a legitimate argument based on when someone believes life begins. But some protests I heard were from people worried about embryonic stem cells being used to clone humans. What I can't figure out is why anyone would want to clone someone.

Cloning won't be like it is in the movies. Scientists won't take a cell from someone and make an exact copy of a person who is the same age and has the same memory.

Instead, a human will be cloned like any other mammal. First they'll remove the DNA-containing nucleus from an egg. Then they'll fuse that egg with a cell from the person they want to clone.

This "fertilized egg" will then have to grow and develop in a surrogate mother, be born, and then have to grow up. The clone won't have any of the original's memories.

In essence, a clone would be more like an identical twin who has been reared apart from his or her twin. Even though identical twins reared apart have a lot of similarities, they have a lot of differences, too. One article I saw put the amount of behavior/personality similarity due to genes at something around 50%.

And a clone will probably be more different than that. When the cell's nucleus is put into the egg, scientists erase a lot of the markings on the DNA that originally turned it into an adult cell. This "fertilized egg" is now a blank cell which can be shaped by both its genes AND its environment.

Identical twins develop in the same womb at the same time and so are exposed to the same sorts of environmental effects. A clone would not be. And these environmental factors can affect how we develop. They can even alter DNA and as a result, alter who we become.

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Soon after Barack Obama is sworn in as President next week, he is expected to reverse George Bush’s executive order limiting embryonic stem cell research. Scientists say their research has been stifled by restricting them to existing stem cell lines. The resulting boom in this cutting-edge medical technology will benefit California's research institutes in a big way.

Researchers call stem cell technology a "revolution" in medicine, along the lines of the development of antibiotics in the 1940s, or the manufacturing of insulin and other therapies from recombinant DNA breakthroughs.

But why do stem cells offer such promise?

Robert Klein, chair of the governing board for the California Institute of Regenerative Medicine (the state stem-cell agency created by Proposition 71), says that the recombinant DNA revolution in the 1970s saved the life of his son, and that the potential for saving lives is even greater with stem cell work.

Stem cell technology has only existed for a decade. And despite the Presidential ban on use of new lines of embryonic stem cells, the advances in research have happened quickly. And, according to Deepak Srivastava, Director of Cardiovascular Research at the UCSF Gladstone Institute, the many possible applications of stem cell work will be seen in the short term (over the next few years) and long term (regeneration of damaged organs could happen in 7 to 10 years, he says).

Dr. Srivastava says, in the case of one of his patients, five-month-old Ryder Ortiz, stem cell technology could have been a godsend. And it might still BE a godsend, he adds. Ryder was born without a left ventricle, the heart chamber that shoots blood into the body. With stem cell technology, it may become possible to grow a new ventricle, and that would’ve been a huge boon to the infant Ryder.

But here's the thing: Doctors jerry-rigged Ryder's circulatory system, and it's a process that works – until the patient hits his teen years. In many cases, that’s when the re-worked circulatory system fails. Now, if Dr. Srivastava's estimate is correct, and the technology develops in the next 7 to 10 years, that will be just in time for Ryder Ortiz, who will be inching nearer to adolescence at that time.

Listen to the New Life for Embryonic Stem Cell Research radio report online.

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