Stem cell that grows into bones, cartilage isolated in mice

US researchers said Thursday they have discovered the stem cell in mice that gives rise to bone, cartilage and a key part of bone marrow called the stroma, offering hope for a wide range of potential therapies for skeletal disorders such as bone fractures, osteosarcoma or damaged cartilage.

"Millions of times a year, orthopedic surgeons see torn cartilage in a joint and have to take it out because cartilage doesn't heal well, but that lack of cartilage predisposes the patient to arthritis down the road," co-senior author Michael Longaker, professor of the Stanford University, said in a statement.

"This research raises the possibility that we can create new skeletal stem cells from patients' own tissues and use them to grow new cartilage," Longaker said.

The study, described in the U.S. journal Cell, started by focusing on groups of cells that divide rapidly at the ends of mouse bones, and then showed that these collections of cells could form all parts of bone: the bone itself, cartilage and the stroma - - the spongy tissue at the center of bones that helps hematopoietic stem cells turn into blood and immune cells.

Through extensive effort, the researchers then identified a single type of cell that could, by itself, form all these elements of the skeleton, and found how skeletal stem cells worked.

In addition, they found how to create skeletal stem cells themselves out of fat or muscle cells.

Now that the researchers have successfully mapped the skeletal stem cell system in mice, they are confident that they will be able to do the same in humans.

"If this is translated into humans, we then have a way to isolate skeletal stem cells and rescue cartilage from wear and tear or aging, repair bones that have nonhealing fractures and renew the bone marrow niche in those who have had it damaged in one way or another," said Professor Irving Weissman, the other senior author of the paper, who is also from the Stanford University.