A group of Japanese researchers have just released a study that advances our understanding of how we can use a specific type of stem cells to help patients recover from cartilage damage. This group worked with a specific type of stem cell called bone marrow-derived mesenchymal stem cells (BMSCs) because these cells confer a number of advantages over other types of stem cells that have been used to repair cartilage. Though one particular type of stem cells, called autologous chondrocytes, have been implanted over 20,000 times for therapeutic reasons, these cells are associated with long and arduous surgeries because it is difficult to harvest the required cartilage and periosteum. Another type of stem cell, referred to as suspended cultured chondrocytes, on the other hand, have the potential to result in leakage, with an uneven distribution of cells throughout the site.
Unlike these other stem cell options, BMSCs can be easily harvest through methods that are relatively minimally invasive. The team in Japan also believes that BMSC implantation is safe, as they observed no tumors or infections in the more than 6-year follow-up period of their study. Nonetheless, previous work with BMSC showed that the cells did not lead to the generation of cartilage that was sufficient to replace old cartilage. To overcome that problem, these scientists decided to explore ways to provide large numbers of cells over a short period of time. Because BMSC from humans lose their ability to differentiate into different types of cells after having traveled long distances, the researchers believed that injecting cells directly into the injury site would improve the chances that good cartilage would develop. In addition, adding a specific agent, called, fibroblast growth factor (FGF-2) could help the cells proliferate.
In this study, the researchers tested these ideas to help determine the ideal conditions for transplanting BMSCs for cartilage repair. They found that their method of transplantation led to better cartilage development than was seen in controls, with rats receiving BMSC treated with FGF-2 directly into the area with cartilage injury having higher Wakitani scores. Wakitani scores are used to assess the regeneration of cartilage tissue and how well the new tissue is integrated into the surrounding tissue.
Given that many cartilage defects do not tend to repair themselves and can often lead to osteoarthritis, it is important to find effective ways to regenerate cartilage. There are a number of limitations to the current therapies, but this study demonstrates how our tools for cartilage repair are progressing and the promise of stem cells to help rebuild defective cartilage.
Itokazu et al. (2016). Transplantation of scaffold-free cartilage-like cell-sheets made from human bone marrow mesenchymal stem cells for cartilage repair. Cartilage, 7(4), 361-372.