Written By Osayenmwen Omozusi

        Regenerative medicine is a promising field working to restore the structure and function of damaged tissues and organs. Additionally, regenerative medicine is working on finding solutions for permanently damaged tissues. Researchers are now discovering that cartilage in human joints could perhaps repair itself in a manner similar to animals such as axolotl, zebrafish, and bichir also exhibit. This possibility of cartilage regeneration could lead to a possible cure in arthritis, which is an inflammation of the joints. The study’s focus was cartilage regeneration in the hip, knee, and ankle regions.

        Young proteins play an important role in the recovery and repair of tissues in the muscles, skin, organs, blood, hair, and nails. In the study, they found that young proteins help cartilage regeneration. They determined that the hip had the lowest amount of young proteins, while the knee had slightly more proteins than the hip, and the ankle had had the highest amount of young protein. The researchers devised a way to determine the age of proteins to discover the mechanisms behind these findings.

           Professor Kraus, a professor at Duke University, and colleagues found the age of proteins using internal molecular clocks integral to amino acids, which convert one form to another with predictable regularity. They discovered that newly created proteins in tissue have few or no amino acid conversions, but as proteins become older, they have many amino acid conversions. Similarly, the age of cartilage largely depended on where it resided in the body. Cartilage in ankles is young, while it is middle-aged in the knee and old in the hips. The younger the proteins are, the more efficient they are at healing.

           Scientists also discovered that microRNA regulates the process of how long an area will heal. MicroRNAs are more active in animals that are known for limb, fin or tail repair, including salamanders, zebrafish, African freshwater fish and lizards. These microRNAs are also found in humans — an evolutionary artifact that provides the capability in humans for joint tissue repair. As in animals, microRNA activity varies significantly by its location: it is highest in ankles compared to knees and hips and higher in the top layer of cartilage compared to deeper layers of cartilage. Scientists like Dr. Ming-Feng Hsueh who research arthritis, are calling this the “inner salamander capacity” because it displays how possible cartilage regulation can take place. The study of microRNA will advance medicines that could prevent, slow or reverse arthritis. Kraus says she is “very hopeful” that the findings could lead to therapies. One day, they also might discover how to regenerate part or all of a human limb. Potentially, she suggests, microRNAs could be “Injected directly into a joint to boost repair to prevent osteoarthritis after a joint injury or even slow or reverse osteoarthritis once it has developed.”

        Although we still have a long way to go to explain why humans cannot regenerate, this study provides compelling evidence that there are many similarities between human and salamander limbs. As stated by Professor Kraus, “If we can figure out what regulators we are missing compared with salamanders, we might even be able to add the missing components back and develop a way someday to regenerate part or all of an injured human limb.” This is only the beginning of regenerative medicine. In the future, it could be applied to other tissues, not just cartilage.

References:

Hsueh, M.-F., Önnerfjord, P., Bolognesi, M. P., Easley, M. E., & Kraus, V. B. (2019, October 1). Analysis of “old” proteins unmasks dynamic gradient of cartilage turnover in human limbs. Retrieved November 4, 2019, from https://advances.sciencemag.org/content/5/10/eaax3203.

News Staff. (2019, October 10). Humans Have Ability to Regrow Damaged Cartilage, Study Reveals. Retrieved November 4, 2019, from http://www.sci-news.com/biology/humans-regrow-cartilage-07683.html.

Williams, S. (2019, October 10). Adult Humans Can Regenerate Cartilage: Study. Retrieved November 4, 2019, from https://www.the-scientist.com/news-opinion/adult-humans-can-regenerate-cartilage–study-66558.