Step forward in stem cell control

URL: http://news.bbc.co.uk/hi/english/sci/tech/newsid_963000/963961.stm

 Monday, 9 October, 2000, 22:20 GMT 23:20 UK

BBC News Online

              Scientists have reached another milestone in

              their quest to create "spare part" tissues for

              transplant using human embryonic stem cells.

              Researchers in the US and Israel have

              discovered a way to direct the early

              development of these special cells in the lab.

              The international team used eight different

              growth factors - body chemicals that influence

              cell development - to encourage embryonic

              stem cells into becoming the three primary cell

              types known as ectoderm, endoderm and

              mesoderm.

              It is these cell lines that go on to form the

              different tissues in the body, including muscle,

              bone, skin and nerves.

              Immune system

              Scientists think that if they can obtain full

              control of this process they will be able to

              "grow up" replacement tissues to treat a range

              of degenerative diseases in which specific cell

              types have become damaged.

              If the technology is married to that of cloning,

              it may even be possible to create

              perfect-match tissue that is not rejected by

              the patient's immune system.

              The scientists, from the Hebrew University,

              Jerusalem, and the Howard Hughes Medical

              Institute, at Harvard University, Cambridge,

              Massachusetts, report their findings in the

              Proceedings of the National Academy of

              Sciences.

              In one experiment, growth factors were used

              to encourage human embryonic stem cells to

              develop mainly into a cell type known as

              mesodermal, which eventually forms muscle,

              blood and skeleton.

              Inhibiting development

              In another experiment, the stem cells were

              directed into becoming mesodermal or

              ectodermal cells. Ectodermal cells include

              those of the skin and brain.

              A third category of growth factors permitted

              stem cells to grow into any of the three basic

              layers of cells: mesodermal, ectodermal or

              endodermal. Endodermal cells include those of

              the liver and pancreas.

              The team found that most of the growth

              factors worked by inhibiting, rather than

              promoting, certain kinds of cell development.

              This suggested that control of embryonic stem

              cell development might also be achieved by

              using compounds that block the action of

              growth factors, they said.

              Ethical debate

              The authors wrote: "These results represent

              an initial step toward achieving fully directed

              cell differentiation and open the way to

              combining growth factor incubation with

              selection methods."

              The use of human embryonic stem cells in

              research has become a highly controversial

              topic. The cells are sourced from unwanted

              IVF embryos or aborted foetuses.

              This has prompted a major ethical debate

              which has intensified because of the desire of

              scientists to also use cloning technology in

              their studies.

              In the UK, an expert panel spent almost a year

              examining the moral and technical issues

              relating to stem cells and their use in so-called

              therapeutic cloning and recommended research

              should be permitted.

              Politicians will have the final say.