SUSAN DENTZER: Human stem cells hold out the potential of almost unimaginable medical breakthroughs. That's because they're a kind of universal cell that can develop into most of the specialized cells and tissues of the body. And that means new tissues or entire organs could one day be grown in a lab, then used to treat everything from heart disease to spinal cord injuries.
DR. JOHN GEARHART, Johns Hopkins School of Medicine: Just think about it. We have a renewable cell source in a laboratory setting that we can then take at our desire to then produce a specific cell type. I mean, it's kind of mind boggling when you think about it.
SUSAN DENTZER: As a result, stem cell research is booming, leading to a burst of developments reported in medical journals. Just last month, studies in the journal "Nature Medicine" reported that stem cells had been used to patch up heart damage in mice. For all the excitement that such techniques could one day be used on humans, much stem cell research has been controversial. That's in large part because of the cells' origin. Although human stem cells can be found in adult bone marrow and other tissues, they're frequently obtained from human embryos that are just days old. Many of these embryos were created through fertility treatments, such as in vitro fertilization, and for various reasons were unused or discarded.
SUSAN DENTZER: But abortion opponents have also been concerned that embryos used in stem cell research could also come from aborted pregnancies. The resulting ethical uproar has cast a cloud over stem cell research. Last year, President Clinton issued guidelines prescribing what aspects of the research could be conducted with federal dollars. President Bush is considering tightening those guidelines even further.
PRESIDENT GEORGE W. BUSH: (January 26) I believe we can find stem cells from fetuses that died a natural death. I do not support research from aborted fetuses.
SUSAN DENTZER: But now new advances in stem cell research may offer a way out of this ethical quagmire. This week, scientists from UCLA and several other centers reported that they had isolated cells that behaved strikingly like stem cells. The cells came from a surprising source: The fat of adult human beings, obtained through liposuction.
DR. MARC HEDRICK, UCLA School of Medicine: It's a different way of thinking about fat tissue. Fat tissue is -- I think now we can consider it not just a spare tire that some of us have around our waist. It's really a tissue that's got a lot of different constituent components, and one of those components happens to be stem cells.
SUSAN DENTZER: In effect, the scientists had taken a glob of fat and removed some cellular material, leaving behind a mixed bunch of cells that went on to multiply. Although it's not certain that these cells actually were stem cells, with the aid of chemicals they were made to behave just like them. The scientists used tests to verify that the cells had grown into other types of cells including muscle, cartilage, bone, or even more fat cells.
DR. MARC HEDRICK: It's a way of allowing us to make tissues in two dimensions in the laboratory as sort of a prelude to then going into animals or humans. So this shows fat, bone and this shows us a blue staining that shows us that we've made cartilage.
SUSAN DENTZER: Still another development reported this week came from a New Jersey-based biotechnology company, Anthrogenesis Corporation. It said it had obtained stem cells from human placentas that are delivered after babies are born and that are normally discarded as medical waste. Again with the aid of chemicals, the cells were grown into nerve, blood vessel and muscle cells. Much remains to be done to establish whether all these types of stem cells hold therapeutic promise, but for now researchers are clearly excited.
DR. MARC HEDRICK: I think this changes the debate with regard to embryonic stem cells. It lets some of the air out of the balloon. If we all are carrying around our own reservoir of stem cells, then we may not need to take human fetal or embryonic tissue and use those cells.
SUSAN DENTZER: And if the ethical cloud over stem cell research really is about to part, still more promising findings probably lie ahead.