How to Fix Arthritis in Damaged Knee

By stimulating cells to reproduce, electricity has already been shown to help heal soft tissue injuries. Now, an electricity-producing implantable material likewise appears to boost the regrowth of cartilage in compromised joints. In a study conducted at the University of Connecticut, a team led by Asst. Prof. Thanh Nguyen and postdoctoral fellow Yang Liu explored the use of a “tissue scaffold” made out of nanofibers of a biodegradable polymer known as poly-L lactic acid (PLLA). It had previously been used to accelerate the healing of broken bones.

So-called tissue scaffolds take their name from the fact that they have a scaffolding-like three-dimensional internal structure, which acts as a sort of roosting place for adjacent cells to migrate into and reproduce. Eventually, the scaffolding dissolves and is replaced entirely by the cells, resulting in a solid piece of biological tissue.

Unfortunately, according to the scientists, joint cartilage that has been regrown using conventional scaffolds has tended to be weaker than the original cartilage, causing it to quickly break down under regular use. That’s where the PLLA comes in. Along with being biocompatible, it’s also a piezoelectric material, meaning that it produces a small electrical current when mechanically stressed. Therefore, it was believed that if a tissue scaffold made of the material were to be implanted in an arthritic knee joint, it would continuously produce cartilage-boosting electricity as it was squeezed during activities such as walking. In order to test that theory, pieces of the material were placed in the injured knee joints of rabbits, which regularly hopped on a slowly-moving treadmill. It was found that after one to two months, strong, robust cartilage proceeded to grow back within the joints. By contrast, a control group that received non-piezoelectric tissue scaffolding experienced little healing of the damaged cartilage.

Importantly, the material didn’t contain any chemical growth factors, which may cause unwanted side effects. The researchers now want to test the technology on larger, older animals, and to monitor the regrown cartilage for at least a year or two.


How To Heal Arthritis

Osteoarthritis, a disease that causes severe joint pain, affects more than 20 million people in the United States. Some drug treatments can help alleviate the pain, but there are no treatments that can reverse or slow the cartilage breakdown associated with the disease.

In an advance that could improve the treatment options available for osteoarthritis, MIT engineers have designed a new material that can administer drugs directly to the cartilage. The material can penetrate deep into the cartilage, delivering drugs that could potentially heal damaged tissue.

Six days after treatment with IGF-1 carried by dendrimer nanoparticles (blue), the particles have penetrated through the cartilage of the knee joint.

This is a way to get directly to the cells that are experiencing the damage, and introduce different kinds of therapeutics that might change their behavior,” says Paula Hammond, head of MIT’s Department of Chemical Engineering, a member of MIT’s Koch Institute for Integrative Cancer Research, and the senior author of the study. Treating  rats, the researchers showed that delivering an experimental drug called insulin-like growth factor 1 (IGF-1) with this new material prevented cartilage breakdown much more effectively than injecting the drug into the joint on its own.

Brett Geiger, an MIT graduate student, is the lead author of the paper, which appears in Science Translational Medicine.