The mechanical stresses of normal exercises are key for the health of the meniscus (a layer of buffering tissue in the knee joint). Researchers from 2 medical centers have found, however, that these stresses, paired with a strong immune system response, can lead to the ultimate degeneration of the knee joint as seen in osteoarthritis.
Furthermore, the chemical nitric oxide is an important indicator in controlling how the immune system responds to stress.This discovery could lead to new therapies for osteoarthritis that would target this interaction between nitric oxide and the inflammatory response, according to the researchers. They took samples of meniscus from pigs and subjected these samples to various pressures under different conditions. Then they compared the samples that reacted to mechanical stress with those that did not. The investigators learned that the samples that underwent compression showed a dramatic increase in the production of the meniscus. For example, protein synthesis increased 68%, and proteoglycan, the substance that gives the meniscus its ability to absorb shocks, increased by 58%.
Because interleukin-1 (IL-1) plays a role in the destruction of cartilage with osteoarthritis, the researchers did compression experiments in the presence of IL-1. ?We found that the stimulatory effect of the mechanical stress was prevented by the presence of IL-1,? said Farshid Guilak, PhD, director of orthopedic research at Duke University Medical Center. This finding suggests that an inflammatory environment may alter the physiological response of the meniscus to mechanical stress.?
The researchers also found another interesting result. If they inhibited the synthesis of nitric oxide, the beneficial effects of mechanical stress returned, even in the presence of IL-1.