May 2022

Regrowing Knee Cartilage with an Electric Kick

Image of the tissue scaffold, courtesy of Nguyen.

University of Connecticut (UConn) bioengineers successfully regrew cartilage in a rabbit’s knee, a promising hop toward healing joints in humans.

The lab of UConn bioengineer Thanh Nguyen, PhD, has been working on cartilage regeneration, and they’ve discovered that electrical signals are key to normal growth. They designed a tissue scaffold made out of nanofibers of poly-L lactic acid (PLLA), a biodegradable polymer often used to stitch up surgical wounds. When squeezed, this piezo-electric nanomaterial produces a little burst of electrical current. The regular movement of a joint, such as a person walking, can cause the PLLA scaffold to generate a weak but steady electrical field that encourages cells to colonize it and grow into cartilage. No outside growth factors or stem cells (which are potentially toxic or risk undesired adverse events) are necessary, and crucially, the cartilage that grows is mechanically robust.

The team recently tested the scaffold in the knee of an injured rabbit. The rabbit was allowed to hop on a treadmill to exercise after the scaffold was implanted, and just as predicted, the cartilage grew back normally. “Piezoelectricity is a phenomenon that also exists in the human body,” said Yang Liu, PhD, a postdoctoral fellow in Nguyen’s group. “Bone, cartilage, collagen, DNA, and various proteins have a piezoelectric response. Our approach to healing cartilage is highly clinically translational, and we will look into the related healing mechanism.”

Nguyen’s lab wants to observe the animals treated for at least a year, probably 2, to make sure the cartilage is durable. And it would be ideal to test the PLLA scaffolds in older animals, too. Arthritis is normally a disease of old age in humans. Young animals heal more easily than old—if the piezoelectric scaffolding helps older animals heal as well, it could be a bioengineering breakthrough.

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