Therapeutic cloning involves the replication of human embryos to harvest stem cells for medical uses. Most clones are created through a process called "somatic cell nuclear transfer." Essentially, a scientist uses a tiny needle to pull DNA material from the nucleus of a donor cell and transfer it into a hollow egg. The egg has had its own nucleus and genetic material removed. To get this hybrid cell to start dividing, lab technicians then "stimulate" the egg with a chemical bath or a jolt of electricity.
Instead of implanting the resulting embryo into a female host, as would be done in reproductive cloning, scientists destroy the embryo so that researchers can extract the stem cells. Stem cells are pluripotent; they have the potential to form any cell or tissue in the human body. They are master cells, capable of morphing into cells in the brain, muscles, or other organs, and which might be used for medical treatment.
In 2001, Great Britain became the first country in the world to legalize the creation of human embryos -- not to create living human clones, but to create embryos whose stem cells can be taken for experimental use. Under new regulations, these clones must be destroyed after 14 days, and it is illegal to create live babies by cloning.
Many scientists who urge a ban on reproductive cloning urge that the ban not be extended to therapeutic cloning and the harvesting of stem cells to cure disease. Scientists say the use of stem cells to grow new cells has the potential to treat or cure dozens of degenerative diseases, from heart disease to Parkinson's to kidney failure.
"I am convinced that therapeutic cloning offers health opportunities that you could not attain in any other way," says Ian Wilmut, adding that it shouldn't be banned along with reproductive cloning (NewScientist.com, November 7, 2003). Wilmut is the scientist who cloned Dolly, the sheep, in 1996 and is now a leading commentator on the subject of cloning.
Responding to fears that if therapeutic cloning is allowed, some renegade researcher may decide to implant a cloned embryo, rather than destroy it, Wilmut says, "We can't stop this valuable research from going forward for fear of a few bad apples out there. That's why there are laws."
STEM CELL TREATMENTS FOR PARKINSON'S DISEASE
Could stem cell technology help reverse the physical decline suffered by Parkinson's patients?
Many scientists say yes. Renowned stem cell expert, Swedish researcher Olle Lindvall, in an article at NewScientist.com (November 7, 2003), says he expects to be able to transform stem cells into the dopamine-producing neurons Parkinson's patients so badly need. But it will take time.
"Stem cells could potentially be used for the treatment of Parkinson's disease -- but it's a very difficult problem to generate large numbers of dopamine-producing neurons, which are the cells we need," Lindvall says. "I am convinced that stem cell technology can become in the future a cure for conditions leading to brain injury -- but I think we have a long way to go."
Scientists have had some success treating Parkinson's in animals using stem cells from aborted animal fetuses, Lindvall says, but those stem cells aren't as effective as the ones harvested from very early embryos of just a few days old.
And there is another possibility. Linvall's research has shown that the brain of a rat, after a stroke, actually produces new brain cells that travel to the damaged area. Perhaps that process -- plus some encouragement from drugs and combined with stem cells treatments - may be the eventual treatment for Parkinson's.
CLONING FOR STEM CELLS
"Our intent is to use this technology to generate stem cells to treat serious and life-threatening diseases, not to create a child," says Robert Lanza of Advanced Cell Technology (ACT) in an article in "Scientific American" (January 2002). He told me that his is one of the very few efforts in the world that has successfully cloned a human embryo. ACT is one of the very few private companies in the United States that kept working on stem cell research after the U.S. government dried up federal funds for the procedure.
Think of an embryonic stem cell as a kind of master cell, an early-stage cell that retains the ability to form almost any kind of cell or tissue type in the human body. With a little chemical encouragement, a stem cell can turn into a new heart muscle for a heart attack victim; new neurons for stroke, paralysis or Parkinson's patients; or new insulin-secreting pancreas cells for diabetics. Down the road, scientists believe it will be possible to create such complicated structures as blood vessels, liver tissue, and whole kidneys. In fact, ACT scientists have already succeeded in building tiny cow kidneys that could be used for kidney transplants. It isn't hard to envision, Lanza says, a future where pretty much any kind of organ or tissue could be engineered to replace those damaged by age, injury, or disease.
"It's not science fiction at all. This field is moving ahead so phenomenally quickly that by the time the baby boomers age, this could be routine stuff," says Lanza, in an interview with the author (December 15, 2003). Lanza adds that scientists have already developed techniques that could cure macular degeneration, a malfunction of the retina that leads to poor vision and blindness in more than 1.7 million Americans. But getting such techniques into the clinical trial stage is quite another matter. "We only have eight scientists and thanks [to the federal funding ban], there are times when we can barely make payroll. "My hope is that as soon as we can show that we can cure diabetes in dogs, people will clamor for this. And then," Lanza says, "everything will change."
RESEARCHERS CREATE JOINT FROM STEM CELLS
Scientists say they've managed to build the ball-structure of a joint from adult stem cells retrieved from a rat's bone marrow.
Working at the University of Illinois in Chicago (UIC), researcher Jeremy Mao says he succeeded in transforming stem cells into the bone and cartilage tissue of a human jaw joint. "This represents the first time a human-shaped [jaw joint] with both cartilage and bone-like tissues was grown from a single population of adult stem cells." Mao, who is director of the University's tissue engineering laboratory and a professor of bioengineering and orthodontics, was speaking at a UIC press conference on December 1, 2003.
"Our ultimate goal," adds Mao, "is to create a [jaw joint] that is biologically viable -- a living tissue construct that integrates with existing bone and functions like the natural joint." So far tested only in animals, the procedure promises to lead to technology that may help doctors replace hip, knee, and shoulder joints that are damaged by arthritis or other disorders.
The procedure is relatively straightforward. First, researchers prodded the stem cells, with appropriate chemicals, nutrients, and growth hormones, to turn into cells capable of producing cartilage and bone. Then they separated the cells into two layers and poured them into a mold created by the jaw bone of a human cadaver. After a few days, researchers were delighted to discover that they had what they were looking at -- joint-shaped tissue that had bone on the inside and cartilage on the outside, just like a human joint.
Tests confirmed that the engineered tissue actually was bone and cartilage, with all the typical components they have, including calcium and cartilage.
Generally, adult stem cells - that is, stem cells found in bone cartilage - aren't as versatile as stem cells harvested from embryonic tissue. But this study suggests adult stem cells may be more useful than previously thought.
STEM CELLS MAY TREAT MUSCULAR DYSTROPHY
Studies in mice show that a type of stem cell in blood vessels could help patients suffering from the muscle-wasting disease, muscular dystrophy (MD).
Researchers in Milan and Rome have discovered that blood vessel stem cells actually cross from the bloodstream into muscular tissue, where they help generate new muscle fibers. It worked in mice with symptoms similar to those generated by MD, researchers say.
"Although these results are exciting, we have not cured the mice," said Giulio Cossu of the Stem Cell Institute of Milan, speaking at a press conference at the American Association for the Advancement of Science on July 10, 2003. "We believe this is a significant step toward therapy, but the question that keeps me awake at night is whether this will work in larger animals."
This particular kind of stem cell is new to scientists, having only been discovered a year ago. According to Cossu, they are still learning how to identify them by appearance and function, and they've so far only isolated them from fetal blood cells. Moreover, researchers need to refine the part of the procedure that involves inserting a healthy version of the gene that causes MD into the stem cell. Only more experimentation will show whether the procedure will ever be safe enough for humans.
As far as Cossu's mice go, they definitely improved as a result of the procedure. After treatment, their muscles were larger and had more muscle fibers. They were also able to walk on a wheel for a longer period of time than untreated animals. "I'm convinced this is an important result, but this is still not the therapy - for mice or for patients," Cossu told the press, underlining that the technique is still very much experimental.
In the meantime, the debate rages on. President George W. Bush has made no secret of where he stands on the issue of stem cell research. In a televised address to the nation in August, 2001, he said, "We recoil at the idea of growing human beings for spare body parts, or creating life for our convenience."
And the United Nations (U.N.), which was prepared to enter into a long-tem treaty to stop scientists from pursuing human reproductive cloning, instead hit a deadlock when the United States, the Vatican, and fifty Catholic countries pressured the U.N. to ban therapeutic cloning, too. The whole issue is now shelved until delegations have put more study into it. The treaty wont come up for discussion again until 2005.
The reaction among scientists varied widely. Some, like Bob Ward, spokesperson for the Royal Society in the U.K., said, "No decision is better than the wrong decision."
In other news reports, some scientists say they felt cheated. "Rather than ban the thing we all agree on, we end up with no ban, because the extremists refuse to compromise," says Larry Goldstein, a stem cell researcher at the University of California at San Diego (NewScientist.com, November 7, 2003)
Some observers are concerned that the U.N.'s delay in banning human reproductive cloning gives scientists hoping to make a big name for themselves or a fast buck from creating human clones some sort of safe haven.
PARTHENOGENESIS: AN EASY ANSWER ?
In January 2004, Lanza and his fellow scientists at ACT made an announcement: They had succeeded in bringing a human embryo to the point of 100 cells through a technique called parthenogenesis. This was important news.
The same kind of reproduction that occurs in snakes and some birds, parthenogenesis leads to the creation of embryos (or "parthenotes") that don't include the male chromosomes required to make a placenta, so they could never be born as a living human. Perhaps stem cells created through this method won't be as controversial, and it could become the primary way stem cells are harvested for therapeutic purposes.
"This is an ongoing research project and there are many steps ahead, including developing the cells into viable therapies," says Lanza.
The whole issue of a looming United States and, possibly, United Nations ban on cloning riles Lanza, who claims that stem cell therapy is the best shot that millions of Americans have to adequately treat their degenerative disorders. "It's unconscionable," says Lanza, "for Catholics and other evangelists to deny others the right to receive medical therapies. It's the whole issue of church and state. Who is the government to be taking sides in these religious debates? They should be looking out for the health and well being of their citizens."
At this writing, the U.S. House of Representatives had passed a bill that bans all forms of cloning. The same measure was stalled in the Senate. In the meantime, Lanza pursues his work while it is still legal -- and waits.