Human egg cells can be tweaked to give rise to valued stem cells that match the tissue types of many different groups of people, U.S. and Russian researchers reported on Wednesday. They said the stem cells they have created from unfertilized human eggs look and act like embryonic stem cells.
And they have been carefully tissue-matched in the same way as bone marrow donations to prevent the risk of rejection if they are transplanted into people.
The team at California-based International Stem Cell Corp. hopes to create a bank of tissue-matched stem cells that could be used as transplants that a patient's immune system would accept.
"The process is efficient, it is relatively safe and it is ethically sound," Jeffrey Janus, president and director of research at the company, said in a telephone interview.
The cells are created by a process known as parthenogenesis, a word that comes from Latin and Greek roots meaning virgin beginning.
It involves chemically tricking an egg into developing without being fertilized by sperm.
Several teams have now created parthenogenetic human stem cells from eggs. Other teams have created similar cells using human skin cells or human embryos.
Writing in the journal Cloning & Stem Cells, Janus and colleagues say they have created four lines, or batches, of stem cells that have specific immune properties. The closer the match, the less likely a transplant will be rejected.
"One of our lines will match 5 percent of Caucasians," Janus said. "One matches 4.7 percent of Native Americans."
A third matches 1.2 percent of African-Americans, he said.
"Our goal is to ... create a bank of stem cells from which a doctor or a researcher could draw," Janus said. "That would make regenerative medicine take one big step closer to reality."
Stem cells are the master cells of the body. Those found in the earliest embryos are powerful because they can form any kind of cell and are virtually immortal in the laboratory.
Using human embryonic stem cells — which can be made from embryos left over from fertility clinics or by using cloning technology — is controversial because of concerns about the sanctity of human life and is restricted in some countries.
Some experts see human eggs as a viable alternative.
International Stem Cell's Elena Revazova recruited women getting fertility treatments in Russia. The women agreed to donate unfertilized eggs left over from the process.
The team managed to get four of the eggs to divide long enough to get stem cells out of them and immune-matched the cells to types known in the population.
They are working to differentiate the cells — to grow them into various tissue and cell types. Janus said the first goals are liver cells, the pancreatic cells destroyed by type-2 diabetes and retinal cells that could treat certain types of blindness.
Some groups believe they can achieve an even better match by growing a patient's own cells. But Janus said that takes time. His company's banked cells could be grown into large batches and frozen, ready for immediate use.
"The biology is sound," cloning and stem cell pioneer Ian Wilmut, director of the Scottish Centre for Regenerative Medicine at the University of Edinburgh and editor of the journal, said in an e-mail.
"The value of such cells remains to be seen and depends upon competing techniques."