Hormone-hardened tendons could help repair torn knee cartilage

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.

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.

Image source: Osaka Metropolitan University.