(McClatchy-Tribune Information Services) -- The human placenta could be an important source of stem cells for curing leukemia, sickle cell disease and other blood-related disorders, a new study reveals.

These stem cells appear to have distinct advantages over the techniques currently used to fight such diseases, and they may one day provide an alternative treatment for people who cannot find matching bone marrow donors, researchers said.

Scientists at Children's Hospital Oakland obtained placentas from consenting women who had cesarean sections at Alta Bates Summit Medical Center in Berkeley.

They found that the placentas contained large numbers of blood-producing stem cells, which they were able to remove and grow in a cell culture.

"Yes, the potential is there," said senior scientist Frans Kuypers. "Yes, you can get them out, and yes, they're viable."

One big advantage of such stem cells is that they do not require the perfect match needed for those who have bone marrow transplants, Kuypers said, because they do not trigger the same strong immune system response.

Today, scientists often seek to cure people who have leukemia and other blood-related disorders by giving them stem cell-rich bone marrow from donors who have closely matched tissue types. The transplanted bone marrow makes healthy blood cells to replace the faulty ones.

But if the donor has a different tissue type, the recipient's body will not recognize the new cells and

will attack them, leading to what is known as graft-versus-host disease.

The placental stem cells, like umbilical cord blood, "are much more tolerant with respect to matching," Kuypers said.

The findings, which will appear in the July issue of Experimental Biology and Medicine, could represent especially good news for African-Americans, Asians and multiracial individuals, who often have difficulty obtaining compatible bone marrow donors.

"Many minorities cannot find a match in the national donor program, and as a consequence of that, they may die," said Dr. Bert Lubin, senior vice president of research for Children's Hospital.

Despite the hopeful signs of placental stem cells, their widespread use is probably several years away. Children's Hospital will seek to raise the money to do clinical trials in humans.

The study serves as an important reminder that research in California should not focus solely on embryonic stem cells, which have the ability to transform into any cell type, said Hanna Mikkola, a researcher with the Broad Stem Cell Research Center at UCLA.

Embryonic stem cells hold great promise, but they also have raised concerns about whether they will form tumors or create an ear, for example, where physicians wanted them to produce blood.

The placental stem cells have already matured to the point where scientists know what they will get -- they will produce red or white blood cells or platelets.

"Nature made them, so they're perfect," said Mikkola, who was not involved with the Children's Hospital study. "That's why bone marrow transplantation has worked so well. We shouldn't ignore putting effort on looking at how we can better utilize the stem cells that have already been made."

Another common way to cure children with blood-related disorders is to transplant them with stem cells from umbilical cord blood. Researchers believe these cells are virtually identical to the ones found in the placenta.

Since 1997, when their sibling donor cord blood transplantation program began, Children's Hospital has cured more than 100 young people with blood-related disorders.

But there is a drawback to this approach: Umbilical cords provide only a small number of stem cells, making adult transplants difficult.

One of the study's more promising findings is that the placenta has a several-fold increase in the number of stem cells compared when with cord blood, which could make it easier to transplant adults and larger children.

Leaders at Children's Hospital were enthused this month to receive a $9.8 million gift from Hayward resident Dolores Jordan to fund research in cellular therapies, including bone marrow and cord blood transplantation.

But more money is needed to further the research on placental stem cells, Lubin said. He and his colleagues expressed frustration that they have not been able to obtain the multimillion-dollar grants that many universities have received from the state agency for embryonic stem cell research, especially since therapies from such research often are many years away.

"No one has been cured by an embryonic stem cell," Kuypers said. "We are able to cure folks with (blood) stem cells, and you have to wonder, what is important?"

Copyright (C) 2009, Contra Costa Times, Walnut Creek, Calif.