By
NICHOLAS WADE, N.Y. Times
The
concept of regenerative medicine -- using the body's own stem
cells and growth factors to repair tissues -- has come closer
to reality with a discovery about the special human cells from
which all bone and connective tissues are derived.
The
discovery bolsters the hope that the cells can in principle be
used to repair bone, cartilage, tendon and many other injured
or aged tissues. The cells would in many cases be derived from
the patient's own bone marrow and thus present no problem of immune
rejection.
Biologists
at Osiris Therapeutics, a privately held biotechnology company
in Baltimore, Md., have shown that the cells, called human mesenchymal
stem cells, can be converted into bone cells, cartilage cells,
fat cells and the stroma cells in the bone marrow that provide
support for blood-forming cells.
The company, named after the ancient Egyptian god of regrowth
and rejuvenation, also has identified special factors that can
be used in the laboratory to drive the cells down each of these
distinct lineages. Its work is described in Friday's issue of
Science magazine.
Dr.
Daniel R. Marshak, Osiris' chief scientific officer, said the
mesenchymal stem cells could be formulated so that, when inserted
in the right place in the body, they would change into the appropriate
tissue.
Tests
in animals show that when the cells are grown on ceramic and put
into bone, they turn into bone-forming cells. If grown in a gel
and inserted into cartilage, they metamorphose into cartilage
cells. If injected into the bloodstream, the cells take up residence
in the bone and turn into stroma cells.
There is no way of knowing how soon treatments derived from the
techniques will be available, but a clinical trial is now under
way with breast cancer patients to explore the cells' stroma-forming
abilities. Lack of stroma to support blood-forming cells may be
why the bone marrow transplants given to cancer patients after
chemotherapy are not always successful.
With Novartis AG, the Swiss pharmaceutical company, Osiris also
plans to test in humans the cells' abilities to form new bone,
tendon and cartilage.
The cells can also be converted to fat cells, which could prove
useful in cosmetic surgery and possibly as material for breast
implants.
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