Meniscus tears are common knee injuries that have long frustrated patients and doctors due to limited repair options. A new 3D-printed hydrogel made from cow meniscus could transform how these injuries heal, according to results of a pre-clinical study published in Bioactive Materials from researchers in the Perelman School of Medicine at the University of Pennsylvania.

The meniscus is a complex structure that serves as a critical shock absorber in the knee and one-size-fits-all treatments aren’t always effective. Through creating a treatment adaptable to the different needs of patients, the researchers believe they may have unlocked a better fix no matter where the injury occurs in a meniscus.

“We developed a hydrogel that can be adjusted based on the patient’s age and the stiffness requirements of the injured tissue, which is important because the meniscus has different biochemical and biomechanical properties that vary depending upon the location in the tissue,” said the study’s senior author, Su Chin Heo, Ph.D., an assistant professor of Orthopaedic Surgery and Bioengineering in the McKay Orthopaedic Research Lab at Penn. “Current treatments, including graft-base methods, do not fully recreate these complex differences, leading to poor healing.”

Hydrogels are flexible, water-absorbing materials commonly found in everyday products like contact lenses and baby diapers. The researchers developed a specialized hydrogel by first extracting proteins from donor cow meniscus tissue. Those proteins then directed new cells to become the right types of repair cells for the damaged meniscus and were used as the basis for the treatment’s structures.

To prevent rejection, the team removed cellular components from the cow tissue while preserving its structural framework. This “decellularization” process reduces the risk of immune reactions when implanted, making the treatment both safer and more effective.

To further customize the hydrogels, Heo and his fellow researchers used 3D-printing techniques to account for the variation in the meniscus tissue. That way, they could more closely match the tissue in the areas they were trying to repair. Mismatched tissues might not heal well.

“In our animal studies, we’ve seen the hydrogel integrate well with the surrounding tissue, potentially offering patients a more complete recovery,” said the study’s first author Se-Hwan Lee, Ph.D., a post-doctoral fellow in the McKay Lab. “It’s a more precise, biologically matched solution. We believe this could outperform current treatments.”

The team is now transitioning from small mammal studies to large animal models.

“Our first clinical goal will be to treat smaller, localized meniscus tears,” Heo said. “Once we have success there, I believe we could expand to more complex injuries in the meniscus.”