Researchers are working on a method of delivering cells for cartilage regrowth in aged joints that doesn't use a porous scaffold in order to guide cell growth, but rather relies on the engineering of specific cell characteristics. In theory this should produce a better end result:
In many cases, the cause of age-related joint pain is a loss of hyaline cartilage, which does not have the capacity to regenerate, meaning once gone it is gone forever. Hyaline cartilage is constituted of chondrocytes and its secretions, extracellular matrix (ECM) proteins, which includes collagens II and XI. They do not include collagen I, which is the primary collagen in fibrocartilage, or scar tissue. The key to a successful recovery then is to introduce into the deteriorated cartilage chondrocytes that secrete only hyaline cartilage ECM proteins.
One of the most common strategies for treating hyaline cartilage damage is autologous chondrocyte transplantation. This technique involves acquiring hyaline cartilage from a biopsy and then transplanting it to the injured site. Because the biopsy is smaller than the area that needs repair, the chondrocytes must be expanded, a task that requires enzymatic digestion of the ECM proteins. Unfortunately, the expansion causes the chondrocytes to secrete collagen I, which is why the presence of fibrous tissue is inevitable after such operations.
To solve this problem, researchers report a new protocol that expands not chondrocytes, but induced pluripotent stem (iPS) cells. When a sufficient number of iPS cells are expanded, the protocol then calls for the researchers to differentiate the cells into chondrocytes. Because these chondrocytes are differentiated directly from iPS cells, there is no need to digest ECM proteins, which avoids the problem of fibrous tissue and allows for only hyaline cartilage to be synthesized. Another advantage to this method is that it avoids the use of artificial scaffolds. In other studies artificial scaffolds are included into the transplant to provide support until the chondrocytes begin secreting their own ECM proteins. However, it is unclear if artificial materials prevent optimal integration into the cartilage. Because the chondrocytes have already begun secreting ECM proteins, they can be transplanted without scaffolds.
The team transplanted their particles into three animal models: mouse, rat and mini-pig, finding positive signs for integration and maintenance. "These findings are only preliminary, but they show good indications of safety. The next step is to find the best conditions for transplantation in larger animals before we can consider patient treatment."