Cartilage damage in the knee, for example from injury or osteoarthritis, is rarely yet to be repaired. Researchers have now tried a new approach on rabbits: They implanted a biodegradable structure made of nanofibers into the affected joint. It was designed in such a way that it generated an electrical voltage driven by the movements of the rabbit. This prompted the cells to make new cartilage. In animals treated this way, the damaged cartilage tissue heals almost completely within one to two months of training. Further studies should clarify the extent to which application in humans can be considered.
Osteoarthritis is the most common joint disease in Germany and one of the main causes of chronic pain. Cartilage in the joints breaks down due to wear and tear and chronic joint inflammation, eventually causing bone to rub against bone. Anti-inflammatory pain relievers can relieve symptoms and slow, but not reverse, breakdown. Previous therapeutic approaches attempted to replace the damaged cartilage with a healthy piece from another part of the body. In doing so, however, the extraction point is injured. Attempts to regrow cartilage in a damaged joint so far have had the problem that the regenerated cartilage was less stable than natural.
Nano scaffold with electrical activity
A team led by Yang Lui from the University of Connecticut has now tested a new approach that aims to regrow cartilage. Whereas earlier experiments typically worked with chemical growth factors, Lewis’s team relied on electrical signals instead. “Studies have shown that cartilage responds to electrical stimulation,” the researchers explain. “Electrical fields promote tissue regeneration.” So the researchers created a framework made of nanofibers that, when subjected to mechanical stress, generates an electrical voltage, called piezoelectricity. As a material they used poly-L-lactic acid, a biodegradable polymer that is used, among other things, to sew surgical wounds.
In fact, with the newly developed scaffold, they succeeded in growing cartilage in a cell culture. To test its effectiveness in real joints, the researchers first caused severe cartilage damage in the knees of several rabbits, similar to those affected by osteoarthritis. They then applied a piezoelectric nano-scaffold to one group of rabbits, and a similar nano-scaffold without piezoelectric activity to the other group. A group without a transplant served as a control group.
almost complete cartilage regeneration
After a four-week recovery period after surgery, the researchers put half of the rabbits in each group on an exercise program. The animals were given the opportunity to jump on a treadmill. As a result of the agitation, the piezoelectric material was compressed and stretched in rabbits with a similar implant, thus generating a weak electric field. After one to two months, the researchers killed the rabbits and examined the extent to which the cartilage had regenerated.
Result: In animals that received the piezoelectric implant and then trained, the damaged cartilage was almost completely regenerated. It didn’t matter if the training lasted a month or two. “Just one month of training resulted in significant cartilage healing and left little room for further improvement,” the researchers explained. In contrast, in rabbits that had not received or trained a piezoelectric implant, cartilage healing was significantly slower.
more study needed
“Piezoelectricity is a phenomenon that is also present in the human body. Piezoelectric reactions occur in bones, cartilage, collagen, DNA, and various proteins. Our approach to healing cartilage is highly clinically applicable, and we include the treatments involved.” Will investigate the mechanism,” says Liu. However, further studies are needed before the results can actually be put into practice. “With our study we have shown that the concept works in principle,” Liu Nguyen says. “The result is fascinating, but we still have to test it on larger animals that are close to humans in terms of size and weight. In addition, animals should be observed for at least one year in future studies to ensure the durability of the cartilage.
Quayle: Yang Liu (University of Connecticut, USA) et al., Science Translational Medicine, doi: 10.1126/scitranslmed.abi7282
