New Biomaterial Achieves What Was Science Fiction Until Now: High-Quality Articular Cartilage Growth

When we move, cartilage helps us do so smoothly and pain-free. It’s a tissue that shapes body parts, such as the ears and the nose. It’s also at the ends of the bones, acting as a flexible element that reduces friction between them and allows movement in the joints. Cartilage is fundamental but delicate, so researchers have recently tried to create it with 3D printers, grow it with stem cells, and repair it with hydrogel injections.

Now, scientists at Northwestern University have developed a new bioactive material that can regenerate high-quality cartilage in knee joints. The tests are going so well that they hope doctors will use this biomaterial to prevent surgery and degenerative disease.

Dancing molecules. Before we get into the details of this biomaterial, we must mention earlier breakthroughs by researchers at the same university. In November 2021, Northwestern investigators developed an injectable therapy that could repair tissue and reverse paralysis after severe spinal cord injuries. They did this using something called “dancing molecules.”

These are synthetic nanofibers of hundreds of thousands of molecules that carry information to cells. Because of their chemical structure, they’re in constant motion, which allows them to properly connect with cell receptors in the body that are also in continuous motion. When linked together, the nanofibers mimic the extracellular matrix of tissue and have shown promising results in cartilage and bone regeneration.

The new biomaterial. The treatment of dancing molecules was relevant. However, Northwestern researchers tested their new biomaterial, which has proven effective in regenerating high-quality cartilage. This rubbery substance is a network of molecular components that mimic the body’s natural cartilage environment.

Instead of using these dancing molecules, the material consists of two components. One is a bioactive peptide that binds to TGFb-1, a protein essential for cartilage growth and maintenance. The other is modified hyaluronic acid, a polysaccharide found naturally in cartilage and the synovial fluid that lubricates joints.

In red, the repaired cartilage. Image | Stupp Group

Field testing. When the peptide and modified hyaluronic acid particles combine to drive the self-assembly of nanoscale fibers that mimic the natural architecture of cartilage, the body’s cells regenerate cartilage tissue. How? Bioactive signals in these nanoscale fibers stimulate our body’s cells to make cartilage.

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In their studies, the researchers injected the material into damaged sheep joints. Interestingly, sheep cartilage is like human cartilage: it’s resistant but difficult to regenerate. In just six months, the researchers observed evidence of cartilage repair, including the growth of cartilage with natural biopolymers such as collagen II and proteoglycans. In smaller animals, cartilage regeneration is even faster.

Improving cartilage. The researchers claim that new cartilage grew to fill the affected areas and that the repaired tissue was consistently of higher quality than the control cartilage. Samuel I. Stupp led the study (as did dancing molecules) and says it has the potential to replace the current method of microfracture surgery. In that surgery, researchers microfracture the bone to induce new cartilage growth. However, the problem is that it forms fibrocartilage, which we have in our ears or nose, and is harder and more fibrous.

It’s different from the hyaline cartilage we have between bones, which is precisely what the researchers created with the new biomaterial (or something similar). The goal is that doctors will be able to use the new material to prevent knee surgeries, treat degenerative diseases such as osteoarthritis, and repair cartilage after sports injuries such as the painful tear of the anterior cruciate ligament, due to a new elastic and soft cartilage for the joints.

Next steps. These continued advances in cartilage regeneration are significant. In 2019, the WHO estimated that nearly 530 million people worldwide suffer from osteoarthritis, a degenerative condition in which joint tissue deteriorates over time. This condition causes the bones to rub against each other during movement, which is very painful and could result in joint replacement surgery.

With this type of biomaterial, the goal is to regenerate the cartilage in a noninvasive way rather than simply replacing the joint. The Northwestern team’s next steps are to continue testing in animals with large, human-like structures to see how the new tissue responds over time and whether doctors can apply the treatment to humans.

This article was written by Alejandro Alcolea and originally published in Spanish on Xataka.

Images | Northwestern University, Stupp Group

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