Researchers Discover New Source of Stem Cells

By Jessica Berman
Washington
25 June 2009

A new study reveals the human placenta, the birthsack that nourishes the fetus in the uterus before it is born, could be an important source of stem cells for curing leukemia, sickle cell disease and other blood-related disorders.

Scientists at Children's Hospital in Oakland, California, obtained discarded placentas from consenting women who had had cesarean sections, or surgeries to remove their newborns before birth.

They siphoned off the blood that circulates throughout the placenta and then extracted stem cells or master cells that can be coaxed with hormones to grow into any kind of tissue in the body. Scientists have been looking for new sources of stem cells because they have the potential to cure a number of diseases, including diabetes.

But in the case of sickle cell disease or thalassemia, a disorder that primarily strikes people of Mediterranean descent, the placental stem cells are already programmed to produce fresh blood after they are infused into patients.

Senior scientist Frans Kuypers at Children's Hospital in Oakland, along with Vladimir Serikov, says the research involving placental stem cells was an attempt to prove that they have the potential to cure blood disorders.

"So, yes they are there, and that's all nice. But the more important part is we can get them out," said Kuypers. "We can get many of them out and we can get them out in a viable form. And can show that these cells are able to transplant and able to engraft. And the impact of that is that we will be able to provide a resource for stem cells to a much larger patient population."

Physicians at the Children's Hospital and Research Center in Oakland have taken stem cells from the umbilical cord blood of newborns to cure their older siblings of blood-related disorders.  

But researchers say there aren't enough of these valuable stem cells in a unit of cord blood to meet the needs of those with serious blood diseases, such as leukemia and sickle cell anemia.  On the other hand, they say a unit of placental blood contains five times as many stem cells as cord blood.

Although a bone marrow transplant can provide an alternative treatment, many patients cannot find a matching donor.

Researchers say one big advantage of stem cells from placentas is that they are less likely to trigger the strong immune system response as stem cells from bone marrow - a response that can lead to rejection.

Kuypers says placental stem cells have a number of other advantages.

"These cells, they are absolutely not controversial in contrast to embryonic stem cells because these are cells that nobody would have a problem with using those cells in any shape or form, which is not necessarily the case with embryonic stem cells," he said. "And more importantly to date, nobody has been cured with an embryonic stem cell and we have been curing people with cord blood-derived stem cells for awhile now. And this just opens up a much bigger opportunity for patients who need it."

Despite the promise of placental stem cells, their widespread use is probably several years away. Children's Hospital is now seeking funds to conduct clinical trials in humans.