Alternative ‘Found’ to Embryonic Stem Cells

American researchers announced a breakthrough in the field of stem cell research this week, with word they had discovered a readily available source of stem cells with many of the highly prized qualities of embryonic stem cells.

The researchers have already manipulated these new cells to produce nerve, liver, bone, fat, muscle and blood vessel tissues and shown that these engineered tissue can function like regular tissue when they are transplanted into mice.

“Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs as well,” said Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in North Carolina.

The announcement represents the culmination of seven years’ work, and suggests there may be a way to deliver on the therapeutic promise of embryonic stem cells, without tangling with the ethically sensitive question of working on material taken from destroyed or discarded embryos.

Many in the medical community believe that embryonic stem cells hold the key to treatments for spinal cord injuries, Alzheimer’s, Parkinson’s and Lou Gehrig’s disease, but researchers working in the field have been stymied by legal and ethical roadblocks.

In contrast, the cells used by Atala and his colleagues were harvested from specimens of fetal amniotic fluid that were taken during amniocentesis, a procedure that is used to test for prenatal diagnosis of certain genetic disorders.

The researchers knew that the amniotic fluid contained a rich variety of immature cell types, but it was not clear whether it also contained a true stem cell, capable of differentiating into a range of specialized cells.

Their investigations revealed that a tiny proportion of the cells in the amniotic fluid, about one percent, were indeed stem cells, with two of the most important properties of embryonic stem cells – their versatility and extensive capacity for self-renewal.

It took several more years, but eventually the researchers from Wake Forest and Harvard Medical School were able to manipulate the cells to create muscle, bone, fat, blood vessel, nerve and liver cells, and later test them in mice.

The results were encouraging: when the neural cells were transplanted into “twitcher” or brain-damaged mice, the engineered cells grew and repopulated the diseased area.

“We saw some return of functionality,” Atala said during a teleconference with journalists.

Similarly, the engineered bone cells were successfully used to grow bony tissue in mice. The scientists also demonstrated that the neural cells could secrete neurotransmitters and that the liver cells were capable of secreting urea, which the liver makes from ammonia.

It will be years before similar experiments can be conducted in humans, and it remains to be seen just how versatile these cells are, but their ready availability will facilitate further research, Atala noted.

“The amniotic fluid is chock full of these fetal cells,” he said. The material, which is presumably shed by the embryo, is available throughout the nine months of gestation and can also be extracted from the placenta after birth.

With more than four million births in the United States every year, it would be easy to collect enough specimens to stock a stem cell bank to supply the transplant needs of the entire nation, he said.

“If one had a bank of 100,000 specimens, one could supply 99 percent of the US population with a perfect genetic match for transplantation,” he said.

The study was published in the journal Nature Biotechnology.

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