Stem cells that regenerate bones and cartilage identified

Researchers, including one of Indian-origin, have identified stem cells capable of regenerating both bone and cartilage in mice.
Researchers at Columbia University Medical Center (CUMC) discovered the cells, called osteochondroreticular (OCR) stem cells, in bone marrow of mice by tracking a protein expressed by the cells.
Using this marker, the researchers found that OCR cells self-renew and generate key bone and cartilage cells, including osteoblasts and chondrocytes.
Researchers also showed that OCR stem cells, when transplanted to a fracture site, contribute to bone repair.
"We are now trying to figure out whether we can persuade these cells to specifically regenerate after injury. If you make a fracture in the mouse, these cells will come alive again, generate both bone and cartilage in the mouse-and repair the fracture. The question is, could this happen in humans," said Siddhartha Mukherjee, assistant professor of medicine at CUMC and a senior author of the study.

The researchers believe that OCR stem cells will be found in human bone tissue, as mice and humans have similar bone biology.

Further study could provide greater understanding of how to prevent and treat osteoporosis, osteoarthritis, or bone fractures.
"Our findings raise the possibility that drugs or other therapies can be developed to stimulate the production of OCR stem cells and improve the body's ability to repair bone injury - a process that declines significantly in old age," said Timothy C Wang, the Dorothy L and Daniel H Silberberg Professor of Medicine at CUMC, who initiated the research.
The study also showed that the adult OCRs are distinct from mesenchymal stem cells (MSCs), which play a role in bone generation during development and adulthood.

Researchers presumed that MSCs were the origin of all bone, cartilage, and fat, but recent studies have shown that these cells do not generate young bone and cartilage.
The CUMC study suggests that OCR stem cells actually fill this function and that both OCR stems cells and MSCs contribute to bone maintenance and repair in adults.
The study is published in the journal Cell.