A torn meniscus, the cartilage in the knee, is a common sports injury, and unfortunately it doesn’t heal well. But researchers in Japan have now identified a hormone that helps repair the cartilage after a surgical treatment.
The meniscus is the C-shaped piece of cartilage in our knees, which cushions the thighbone against the shinbone. This vital tissue is susceptible to injury though, especially during sports. Twisting at the knee suddenly while putting weight on it can tear the meniscus, and many of these injuries won’t heal well on their own.
Treatments are often surgical, implanting donated meniscal tissue or taking parts of a patient’s own tendon and using it to strengthen the weakened meniscus. While that can help alleviate some of the pain, the two tissues have very different functions and so the grafts can lack consistency.
For the new study, researchers at Osaka Metropolitan University investigated a new way to make the transplanted tendon more cartilage-like. The key is parathyroid hormone (PTH), which normally controls calcium levels in the bloodstream and is currently used as a treatment for osteoporosis.
The team found that adding PTH to rat tendons made them tougher, growing a matrix of cartilage and expressing more genes associated with the production of chondrocytes, the cells responsible for cartilage formation. This was found both in cultured cells taken from the Achilles tendons of rats, as well as when it was administered to the tendons in live animals.
Next, the researchers grafted tendons that had been strengthened with PTH into rats that had had part of their meniscus removed. And sure enough, the meniscus repaired itself better in the rats treated with PTH, and prevented secondary damage to the articular cartilage of the knee. Importantly, this didn’t trigger ossification – where soft tissues become too hard and bone-like.
The team found that the expression of genes involved in generating new chondrocytes increased by four weeks after treatment. This suggests that the hormone is acting on either tendon cells themselves, or mesenchymal stem cells within the tendon.
While there’s still plenty of work left to do before this could ever end up in your own aching knees, the team hopes that it could eventually be used to better treat one of the most common sports injuries.
“We have made a highly novel discovery that parathyroid hormone administered to tendons induces tendon cartilage chondrocyte differentiation without ossification,” said Kazuya Nishino, first author of the study. “We hope to improve the outcome of meniscus reconstruction surgery and protect knee cartilage in patients who have their meniscus removed at a young age.”
The research was published in the American Journal of Sports Medicine.
Source: Osaka Metropolitan University