Researchers have isolated a master cell in adult bone marrow that can be directed to grow bone or cartilage. It's a laboratory feat that experts call a major step toward learning to make replacement parts for ailing or aging bodies.
The researchers at Osiris Therapeutics in Baltimore report in the journal Science that they isolated a single cell, called a mesenchymal stem cell, and then grew it into a colony of more than a million cells that could be induced to produce bone, cartilage or fat.
Other experts in the rapidly expanding field of stem cell research applauded the achievement.
"The fact that they can (isolate) a precursor cell like that, and direct it to produce specific cell types, is quite an advance," said Dr. James A. Thomson of the University of Wisconsin, a noted pioneer in stem cell research. "It may be that such cells can eventually be used for therapy and that would be quite exciting."
Stem cells are the body's building blocks. Some, such as pluripotent stem cells, come only from embryos and many people oppose their use in research. Other stem cells, such as the mesenchymal cells used by Osiris, are produced in adults.
Only the pluripotent stem cells from embryos are thought to be capable of growing into any tissue in the body. The mesenchymal stem cells are the parent lines for bone, cartilage, fat, tendon and muscle.
Congress has banned federal financing of research using human embryos, and some lawmakers oppose a National Institutes of Health plan to possibly pay for embryonic stem cell research.
The Osiris work helps move stem cell research from the laboratory into the clinical setting, said Dr. David J. Anderson, a stem cell researcher at the California Institute of Technology.
"If you want to use stem cells to replace damaged tissue, you have to first know how to differentiate those cells in the lab dish before you put them into a patient," he said.
In their work, Osiris researchers, led by Dr. Mark F. Pittenger, grew a single mesenchymal stem cell through more than 20 generations to create about a million cells.
They then altered the culture medium and added proteins that caused the specimens to grow into cell families, or lineages, that would produce bone, tendon or fat, Pittenger said. Other work underway may lead to producing muscle cell lines.
"We've arrived at conditions that allow us a very strong degree of control," said Pittenger. "When we direct these cells to the (cartilage) lineage, almost all of the cells grow to that lineage."
That means it's very likely that researchers will eventually be able to inject specific types of cells into patients, which then would grow into replacement bone, tendon or muscle, he said.
Laboratory research on animals is already underway and human studies may be possible in three years, he said. Research in rabbits and dogs already has shown that gaps in leg bone caused by surgery, such as for cancer, ca be filled in with tissue grown in the body from stem cells.
If the technique proves successful, researchers predict that precursor cells for bone could be used to replace tissue lost to injury, cancer, osteoporosis, or other diseases.
Written By Paul Recer