At joints surrounded by a sac of fluid (synovial joints), such as the knee, articular cartilage forms a thin layer that prevents bone from grinding against bone. Aging and intensive sports erodes or injures articular cartilage resulting in underlying bone to deteriorate, causing considerable pain.

Articular cartilage is composed of glossy and greyish hyaline that does not regenerate easily after injury. Therefore, once articular cartilage is injured, it is important to stabilize the surrounding remaining cartilage and bone, to prevent further deterioration of the joint.

Fortifying and reinforcing the affected cartilage with a surface biocompatible sealant material restores fluid pressure in the tissue and keeps the surface from further loss of fluid and tissue.

A new study reports the development of a hyaluronic acid hydrogel system designed to interlock with the affected articular cartilage like fingers in clasped hands. This securely seals the apposing surface of the affected cartilage.

The interdigitating reinforcement restores tissue mass in and around the affected area and re-establishes mechanical signals similar to cartilage cells (chondrocytes) in the original tissue.

In addition to mechanical cues this hyaluronic acid therapy is also designed to present chemical cues that improve the attachment and responsiveness of stem cells at the affected site, guiding local matrix deposition to further reinforce the affected area.

Details of the testing of this innovative hydrogel therapy in animal models are published in an article in the journal Advanced Healthcare Materials titled, “Stabilization of Damaged Articular Cartilage with Hydrogel‐Mediated Reinforcement and Sealing,” by researchers at the Perelman School of Medicine at the University of Pennsylvania.

“Our research shows that using our hyaluronic acid hydrogel system at least temporarily stops cartilage degeneration that commonly occurs after injury and causes pain in joints,” says Robert Mauck, PhD, professor of Orthopaedic Surgery, director of Penn Medicine’s McKay Orthopaedic Research Laboratory and senior author on the study. “In addition to pausing cartilage breakdown, we think that applying this therapy can present a surface that is ‘sticky’ for cells, such as stem cells that are routinely injected into joints to counteract injury. This reinforcing hydrogel could actually synergize with those cells to create a long-term solution.”

“We often relate this combined approach to treating a damaged deck in your backyard,” says Jay Patel, PhD, a former post-doctoral fellow in the McKay Lab and now assistant professor at Emory University. “To fortify the existing wood structure, you need something like a wood hardener, then you can apply a wood sealer to prevent future wear. In the same way, we applied a substance that seeps into the pores of the tissue and provides reinforcement, then ‘sealed’ it by guiding the behavior of injected stem cells towards forming a layer that caps the whole structure.”

The team combined the hyaluronic acid hydrogel system with an injection of mesenchymal stem cells and stromal cells, to promote the formation of a living barrier on the cartilage surface to protect it from further injury. Comparing models that received the treatment to ones that did not, the researchers found that treated models formed a thicker layer of protective tissue that could protect the cartilage’s structure and preserve function.

“Next, we hope to translate this technology to more large animal studies and to the clinic in the near future,” says Patel.

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