A way to reverse a disease that destroys joints has been found
Osteoarthritis has been linked to depletion of articular cartilage stem cells.Researchers from the University of Adelaide in South Australia have found that osteoarthritis in mice is associated with depletion in articular cartilage of precursor cells that express the GREM1 gene. This condition can be reversed and prevent the development of the disease.
Articular cartilage is composed of specialized chondrocytes, cells that secrete a rich extracellular matrix high in proteoglycans that allow efficient movement between two bones. This tissue requires constant support from progenitor cells to repopulate the chondrocytes. But the regenerative capacity of articular cartilage is limited. Osteoarthritis occurs as a result of injury, chronic mechanical stress, or aging.
By studying the knee joints of adult mice, the researchers found that a specialized population of chondrogenic progenitor cells resides on the articular surface and generates articular cartilage. These cells, which express the GREM1 protein, were depleted in osteoarthritis. In their experiments, the scientists showed that the loss of such cells precedes osteoarthritis and causes the disease.
To discover molecular targets for osteoarthritis treatment, the researchers focused on growth factor signaling to fibroblasts, connective tissue cells that synthesize extracellular matrix and collagen. Treatment of mice with fibroblast growth factor 18 (FGF18) induced proliferation of precursor cells in articular cartilage, leading to significant restoration of its thickness and reduction of osteoarthritis.
It is not yet known whether a similar treatment would work in humans, the researchers note. But in any case, the discovery of the mechanism of osteoarthritis development and a potential target for treatment turns chronic joint "wear and tear" into a condition that can be reversed.