Nanofibers use piezoelectricity to grow cartilage

Robert Klatt

Osteoarthritis cannot yet be cured. Nanofibers, which allow new cartilage to grow thanks to piezoelectricity, are now giving hope.

Storrs (U.S.A.). Osteoarthritis is one of the most common reasons for chronic pain. In joint disease, chronic inflammation breaks down cartilage in joints until bone rubs against bone. So far, medicine has been able to alleviate the symptoms and require the cartilage to be broken down with medication, but not yet reverse it. Therefore, there are only therapeutic approaches in which the degraded cartilage is replaced by healthy cartilage from another body region. However, this leads to injuries at the extraction point.

There have also been attempts to regrow the cartilage in the damaged joint. However, these were not successful because the cartilage that grew back could not achieve the stability of the natural cartilage.

Electrical signals cause cartilage to grow

Scientists at the University of Connecticut have now tested a new method for targeted regrowth of cartilage. According to their publication in the journal Science Translational Medicine, the team led by Yang Lui relied on electrical signals instead of chemical growth factors. “Studies have shown that cartilage responds to electrical stimulation. Electric fields promote tissue regeneration,” explains Lui.

The researchers therefore developed a framework made of nanofibers that, thanks to piezoelectricity, generates an electrical voltage under mechanical stress. The material used is the biodegradable polymer poly-L-lactic acid, which has been used to date, for example, to close surgical wounds.

Cartilage grows in cell culture

In one experiment, the nanofiber scaffold was able to grow new cartilage in a cell culture. The scientists then tested the method on rabbits, which they had previously inflicted with severe cartilage damage similar to that of people with osteoarthritis. A portion of the animals were then implanted with the piezoelectric nanoscaffold. Rabbits implanted with a similar nanoscaffold without piezoelectricity and rabbits that received no implant served as control groups.

Nanoscaffold grows cartilage in rabbits

After a four-week recovery phase, half of each of the three groups completed a training program in which the animals moved on a treadmill. The piezoelectric material in the implant of the first group generated a weak electrical field through compression and expansion. After one to two months, the scientists examined the condition of the cartilage of the previously killed animals.

In the animals with the piezoelectric implant and the training, the damaged cartilage regenerated almost completely. Whether the training was carried out for one or two months made almost no difference to the result. “Even a month’s training led to a significant healing of the cartilage and left little room for further improvements,” say the scientists. Cartilage healing was significantly worse in the animals that did not receive a piezoelectric implant or did not complete the training program.

Further studies with animals

“Piezoelectricity is a phenomenon that also exists in the human body. Bone, cartilage, collagen, DNA and various proteins have a piezoelectric response. Our approach to healing cartilage is highly clinically transferable, and we will study the associated healing mechanisms,” explains Liu.

However, before clinical trials can be conducted with humans, animal experiments still have to clarify open questions. For this purpose, experiments should be carried out with animals that correspond more closely to a human in terms of weight and size. In addition, the animals should be observed for at least one year to ensure that the cartilage has a sufficiently high durability.

Science Translational Medicine, doi: 10.1126/scitranslmed.abi7282




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