Unlike our bones, the cartilage inside our joints is not vascularized (i.e., it has no blood vessels). This is one reason why cartilage does not heal well after an injury. In athletes in particular, joint injuries often result in cartilage degeneration and arthritis. The process is chronic and irreversible, and to this day, no effective treatment exists.
EPFL scientists Dominique Pioletti and Harm-Anton Klok have developed a hydrogel that promotes cartilage regeneration. In a joint, cartilage-producing cells only respond to treatment if they are mechanically stimulated at the same time, for example in the knee joint when a person is walking. To exploit this fact, the scientists created a hydrogel that delivers a therapeutic drug to the cells only when they are undergoing repetitive movement. The results of their work, which is part of the "Smart Materials" Swiss National Research Project (PNR 62), have been published in the journal Biomaterials.
Targeted and timed delivery
The cells that produce cartilage in a joint are called chondrocytes. When a joint is at rest, its chondrocytes are mostly inactive. However, when the same joint is moving, its chondrocytes activate receptors that are sensitive to growth factors produced by the body. At the same time, the chondrocytes become sensitive to treatments that help them regenerate damaged cartilage. "The receptors involved only appear after 5-20 minutes of repetitive movement," says Prof. Pioletti. "We therefore had to develop a way to time the release of the medication."