Lab-grown cartilage grown shows similar mechanical and chemical properties to the natural articular cartilage which allows our joints to move smoothly, according to a new study in Nature Materials. 

A team biomedical engineers from University of California, Davis, created the lab-grown tissue similar to natural cartilage by giving it a bit of a stretch, growing it under tension but without a supporting scaffold. Their results show similar mechanical and biochemical properties to natural articular cartilage. 

Articular cartilage provides a smooth surface for our joints to move, but it can be damaged by trauma, disease or overuse. Once damaged, it does not regrow and is difficult to replace. For that reason, artificial cartilage that could be implanted into damaged joints would have great potential to help people regain mobility.

The top image is the lab-grown cartilage. The simple stress model below shows strain distribution across the artificial tissue. Credit: Athanasiou lab, UC Davis

Natural cartilage is formed by cells called chondrocytes that stick together and produce a matrix of proteins and other molecules that solidifies into cartilage so bioengineers have tried to create cartilage, and other materials, in the lab by growing cells on artificial scaffolds. More recently, they have turned to “scaffold-free” systems that better represent natural conditions. The team grew human chondrocytes in a scaffold-free system, allowing the cells to self-assemble and stick together inside a specially designed device. Once the cells had assembled, they were put under tension — mildly stretched — over several days. They showed similar results using bovine cells as well. The new material had a similar composition and mechanical properties to natural cartilage, they found. It contains a mix of glycoproteins and collagen, with crosslinks between collagen strands giving strength to the material.

Experiments with mice show that the lab-grown material can survive in a physiological environment.  The next step is to put the lab-grown cartilage into a load-bearing joint, to see if it remains durable under stress, like in real-world conditions.