US researchers have identified a novel type of stem cell, derived from amniotic fluid, that they claim has the potential to develop into all types of body tissue. The scientists, working at the Institute for Regenerative Medicine at Wake Forest University School of Medicine, North Carolina, isolated stem cells from fluid left over from diagnostic testing. The new cells are known as AFS cell lines - referring to amniotic fluid-derived stem cell lines. In experiments that have taken over seven years to complete, the team has managed to coax the cell lines to form fat, bone, muscle, nerves, liver and the lining of blood vessels.
Although stem cells are also found in adults and umbilical cord blood, these have only limited ability to be transformed into different types of tissue in the laboratory. Embryonic stem cells are not limited in this way and can potentially be turned into any part of the body. However, the embryos are destroyed in the process making the research controversial. The researchers at Wake Forest, led by Anthony Atala, regard the new cells as an intermediate stage between embryonic and adult stem cells in terms of their potential for transforming into new cell types. Although other groups have managed to grow specialised cell types from amniotic cells, Professor Atala insists that their cells are 'absolutely totally different' from those found by other researchers as they are 'fully undifferentiated' meaning that, in theory, they can become any cell type found in the body. The new cells also show some advantages over embryonic stem cells as they do not seem to form tumours - a potential risk when using embryonic stem cells.
After growing the stem cell lines into new tissue types, the group transplanted them into mice to see the effect in the body. The transplanted cells integrated and produced the correct chemicals, and bone precursor cells injected onto a 'scaffold' seemed to mimic normal bone formation. The AFS cells would be a direct tissue match for the child from whom the surrounding fluid was extracted, but may also have a reduced chance of rejection, compared to adult stem cells, as fetal cells tend to have lower immunogenicity to reduce the chance of the fetus being rejected by the mother. The AFS cell lines appear to be stable in culture for long periods of time and, according to Professor Atala, are easier to grow than human embryonic stem cells.
Professor Colin McGuckin of Newcastle University, who works on cord blood stem cells, described the research as 'thorough'. He said, 'The best thing is to have a variety of stem cell sources to provide the best stem cell for patients. Unless researchers do work to demonstrate there are alternatives to embryonic stem cells, the public won't understand that'. The work was also welcomed by the Catholic Church. Cardinal Javier Lozano Barragan, head of the Vatican's Pontifical Council for Health Pastoral Care told Vatican Radio that he was 'very glad to see this progress in the field of science for the good of humankind'. The work is published in the journal Nature Biotechnology.