Salamanders are known for their ability to grow back damaged or amputated limbs, something thought to be impossible in humans. But findings from a new study suggest that humans may possess a similar ability.
Osteoarthritis is one of the disorders that are linked to the perceived inability of the body to regrow cartilage. It is a common disorder in the United States. The Arthritis Foundation says that about 27 million people in America have this condition, in which cartilage breakdown results in joint pain and stiffness.
Researchers have long believed that damaged cartilage in joints cannot be restored. The reason for this is that the cartilage does not have its own blood supply. Without necessary blood flow, it becomes hard for the tissue to recover from injuries or damage resulting from normal wear-and-tear of the joints associated with aging.
But findings in new research that appeared in the Sciences Advances suggest that the human body might actually have innate ability to repair and regrow cartilage, in a manner similar to salamanders.
Study authors reported that they saw evidence that cartilage in humans has the ability to restore itself to some extent.
“For the first time, we have evidence that the joint has the capacity to repair itself,” said senior researcher Dr. Virginia Byers Kraus, a professor at the School of Medicine, Duke University in Durham, NC.
The researchers said this “inner salamander capacity” varies across different parts of the body – being highest in the ankle and minimal in the hip.
The gradient observed in this regenerative capacity is somewhat similar to that seen in animals that are able to regenerate their damaged limbs.
Kraus and her team developed a method that helped them to assess the “age” of proteins. The idea behind it was that older proteins have undergone more amino acid conversions than younger proteins.
The scientists used this technique to evaluate proteins present in joint cartilage samples obtained during surgical procedures. They found that cartilage in the ankle had the highest amount of young proteins. Cartilage in the knee was somewhat “middle-aged,” while that in the hip had lots of old proteins and comparative few young proteins.
MicroRNAs appeared to be what regulate this molecular process of cartilage restoration. The molecules, which are what enable salamanders to regrow lost or damaged limbs, were more plentiful in ankle cartilage, compared to knee and hip tissue. They were also more abundant in the top cartilage layers that the deeper ones.
The findings seem to explain why there are fewer cases of ankle arthritis, compared to arthritis in both the knee and hips. They also give insight into why ankle injuries tend to heal faster than injuries in the other two areas.
Better understanding could revolutionize tissue repair in humans
Researchers in this study are not exactly saying that humans may be able to regrow lost limbs yet. Rather, they think a better grasp of the key mechanisms responsible for tissue regeneration could be helpful. It may become possible to repair damaged cartilage in people by finding out what salamanders have and that is lacking in humans.
These findings and future ones could transform the treatment of osteoarthritis and other joint issues. They suggest that it may be possible to promote cartilage repair by using injectable microRNA drugs.
There is currently no cure for osteoarthritis. Available treatments only help to manage the symptoms of the disorder, which raises the risk of other serious medical problems such as diabetes and heart disease.
If the researchers are able to figure out those things that salamanders have and humans do not, they could combine such components with microRNAs. Such a “molecular cocktail” may not only help to repair tissue but also potentially help to regenerate whole limbs in humans.
- Humans have a ‘salamander-like’ ability to regrow cartilage, study finds – CNN (https://edition.cnn.com/2019/10/10/health/humans-salamander-regenerate-intl-hnk-scli-scn/index.html)