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© 2011, 2012 Health Futures Digest
| Lost in all the bashing of Advanced Cell Technology (ACT) for giving the impression it had created a human embryonic stem cell line without destroying the embryos from which they were derived (it had actually destroyed 16 embryos to prove the principle) is the vital fact that they have shown it can be done, and that this offers new hope for regenerative therapies slowed by the Bush ban on federal funds for embryonic stem cell research. “Right-to-lifers” should recognize that ACT’s process is still the only real game in town and a far better bet than adult stem cells for producing viable therapies.
Adult stem cells are programmed to die in order to stave off cancer, and we age instead. The good news — though it’s essentially speculation at the moment — is that it just might be possible to interfere with the program so as to stave off both cancer and aging. A major breakthrough involving embryonic stem cells has already been made toward a therapy to repair broken spinal cords. It adds to the evidence of their potential to relieve suffering for some of the most severly afflicted human beings on Earth. It also appears possible that embryonic-like stem cells can be made from adult stem cells. But the proof of the pudding will be in the eating, and so far we have merely sniffed the appetizer. In other news:
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| Stem cells – Oops, Again
A study by Advanced Cell Technology aimed at producing embryonic stem cells without harming embryos actually used 16 embryos donated by couples at fertility clinics. Many news media reported that the embryos had survived the experiments, but in fact they had not. Nature, which published the research, subsequently acknowledged that its own editors had erred in describing the study as “plucking single cells from human embryos” in a way that generated new stem cell lines “while leaving the embryo intact.” Lost in the noise is the fact that ACT’s study did show that is possible to do just that. Two US senators who strongly support human embryonic stem cell research are among the noise makers. One of them called it “a big black eye” for the cause. But ACT insisted that it had “demonstrated, for the first time, that human embryonic stem cells can be generated without interfering with the embryo’s potential for life.” An ethicist who was among several who approved the experimental protocol, told the senators they were wrong to belittle the findings or the way they were reported, wrote Rick Weiss in the Washington Post. “We’re speaking here of an enormous breakthrough in American medicine,” said the ethicist. “Lanza [of ACT] and the senators agreed on one thing,” wrote Weiss: “The quickest way to boost the availability of stem cells for research would be to pass legislation like that recently vetoed by President Bush, which would allow scientists with federal funding to study embryos about to be discarded by fertility clinics.” Aastrom Biosciences announced in June that it had completed the last patient treatment in a clinical trial of its cell-based Tissue Repair Cells for tissue regeneration in severe bone fractures that have not been successfully treated with the current state of the art. The repair cells are a mixture of stem, stromal, and progenitor cells derived from the patient’s own bone marrow. Positive interim data from the first seven patients treated for long bone non-union fractures demonstrated bone healing and return to weight bearing mobility by 6 months with no adverse events. Three US research groups have reported that a gene known for its role in suppressing tumors switches off stem cells as a person ages, reports Nicholas Wade in the New York Times. “It weighs the generation of new replacement cells, required for continued life, against the risk of death from cancer, which is the inevitable outcome of letting cells divide,” and since that risk increases over time, the gene correspondingly reduces the ability of stem cells to divide. As one researcher put it: Aging is “an anticancer program.” The finding casts doubt on the potential of adult stem cell therapies that multiply a patient’s stem cells in the lab and put them back in the patient to build new tissue, and adds to the argument that embryonic stem cell therapies will be more viable. “The notion that adult stem cells are infinite in proliferative capacity is seriously undermined by this work,” said one of the researchers. Another implication is that aging may be hard to cheat. An intervention that prevent the age-related decline of stem cells will also increase the risk of cancer. “There is no free lunch,’’ said one of the researchers, adding cheerily: “We are all doomed.” But another holds out hope that the gene might be induced to switch off temporarily to allow stem cell proliferation without greatly increasing the risk of cancer. Spinal-Cord-Injured Rats Repaired In June, Johns Hopkins researchers reported restoration of movement to paralyzed rats using embryonic stem cells, drugs, and proteins to rewire part of the nervous system. The procedure re-established the electrical path from the rats’ brains, down their spinal cords and out to their muscles. The next step is a study in pigs to determine whether the technique will work in larger mammals, which have longer spinal cords. Clinical trials in humans are possible within five years, but a human therapy is “hundreds of millions of dollars” and many years away. Of 15 rats that received the full treatment, 11 showed significant improvement in their ability to control their hind limbs 24 weeks after the stem cells were implanted. The scientists found that if any one of the factors was removed from the treatment — the stem cells or any of the two proteins and three drugs they used — the rats showed no improvement in their ability to stand and walk. The researchers claim to have found “a blueprint for how to rewire part of the nervous system.” Hitherto, most studies have focused on the nerve cells in the spinal cord that connect to the brain. This one focused on lower motor neurons, which connect the spinal cord to muscles. The researchers say they had to use embryonic stem cells because adult stem cells could not be coaxed into developing into spinal neurons and healthy adult neurons die when implanted into the spinal cord. This means that their research will not be eligible for federal funding if the Bush restrictions remain in force. Researchers at Advanced Cell Technology (ACT) have cultured two fresh human embryonic stem cell lines from single cells taken from an early-stage embryo consisting of 8 to 10 cells. The collection procedure has been used for years in pre-implantation genetic diagnosis (PIGD) prior to in vitro fertilization to be sure that the embryo chosen for transfer into the womb is free of particular genetic disease markers. The resulting stem cells were “true stem cells . . . . virtually indistinguishable from a normal embryonic stem cell,” according to ACT. But the scientific community is not yet fully convinced, and a spokesman for the California Institute for Regenerative Medicine commented: “This appears to add a capability to produce new stem cells lines another way, but it doesn’t amount to a reason to abandon any of the other strategies that are under way.” In PIGD, the embryo generally appears to withstand the loss of a single cell, although only about about 20 percent of in vitro fertilization procedures that follow PIGD succeed. Many stem cell research opponents are against in vitro fertilization and find selecting embryos to implant based on their DNA particularly abhorrent, but a White House spokeswoman told the Los Angeles Times cautiously that the new research appeared to be a step in the right direction. University of Louisville researchers’ success in “coax[ing] stem cells from adult mice to change into brain, heart, nerve and pancreatic cells — mimicking embryonic stem cells” has been confirmed by subsequent independent discoveries at five other laboratories of embryonic-like cells in adults, writes Laura Unger, citing the U of L’s stem cell research team leader. Those discoveries include a similar type of stem cell in human umbilical cord blood, sperm stem cells from adult mouse testes, and “promising” cells in the adult mouse heart. Researchers at the Georg-August University in Göttingen, Germany, cultivated stem cells from a days-old mouse embryo and isolated those that began to develop as sperm (spermatogonial stem cells), which they then grew to adulthood. Female mouse eggs into which these sperm were injected were transplanted into female mice, which produced six babies that lived to adulthood — and many more that died prematurely or displayed abnormal growth patterns. The discovery could eventually help overcome human male fertility problems, but there remain many technical, ethical, and safety issues to be overcome first, and that could take many years. |
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