• Research

    Regenerating the rotator cuff

Preclinical studies discovered a cell-free bioactive material developed at Mayo Clinic triggered healing of one of the most common shoulder injuries. This Mayo Clinic research, published in Biomaterials, documented that purified exosome product —  also known as PEP — promoted repair of rotator cuff injuries faster and more effectively than surgery alone. The rotator cuff is a group of muscles and tendons that surround the shoulder, protecting the socket and guiding mobility.

A rotator cuff tear is a painful condition that leads to disability, limited movement and missed work time. It is estimated that nearly a half-million rotator cuff surgeries are performed in the U.S. every year. However, recurring tears often complicate long-term recovery, sometimes requiring follow-up surgery.

Chunfeng Zhao, M.D.

"Although surgery to repair a torn rotator cuff improves shoulder function, up to 90% of patients re-tear the surgically-repaired tendons because of slow healing," says Chunfeng Zhao, M.D., a Mayo Clinic clinician-scientist and senior author on the study. "Using a rat animal model, we discovered that purified exosome product dramatically improved and accelerated healing. We believe this finding has the potential to be translated to a breakthrough clinical application for patients with rotator cuff injuries. That could have a huge impact on clinical practice and socioeconomic burden."

Regenerative medicine seeks to restore form. Mayo Clinic's Center for Regenerative Medicine is at the forefront of this emerging field, driving new innovations and biotherapeutics that offer new cures for the practice. One of its key priorities is understanding, manufacturing and applying the healing potential of substances such as purified exosome products.

The research

Researchers studied 36 adult rats with rotator cuff tears in the right shoulder. They broke them into three groups: one group was treated with standard surgical repair; the second group was treated with a healing gel used as a carrier for purified exosome product following repair; and in the third group, purified exosome product was added to the healing gel after surgery.

After a recovery time of six weeks, researchers found that the rotator cuff tears in the group treated with purified exosome product repaired more quickly with less inflammation and scar tissue. Moreover, the research team found that those treated with purified exosome product had more newly regenerated collagens and proteins that provide the foundation for muscles, bones and skin. More importantly, the strength of repaired rotator cuff treated with purified exosome product increased significantly compared to other groups.

Cell therapy has shown promise for restoring form and function in rotator cuff tears.

"Accelerating rotator cuff healing has been a hot research topic for decades. Until now, little improvement in outcome has been achieved," says Dr. Zhao. "We found that PEP in the treatment of rotator cuff tears resulted in significant improvement in biomechanical and biological characteristics and shortened recovery time."

An alternative to cellular therapy

Cell therapy has shown promise for restoring form and function in rotator cuff tears. However, hurdles to overcome, including cost associated with manufacturing, and uncertain scalability and standardization hinder clinical translation. Purified exosome products, a cell-free bioactive material, may offer an alternative. They are extracellular vesicles that serve as a delivery service moving cargo from one cell to another, with instructions for healing. This technology is biomanufactured under strict quality control measures in current Good Manufacturing Practice facilities at Mayo Clinic and formulated as a dry powder to enable long-term storage at room temperature. This makes it potentially more convenient and cheaper to use when needed at the point of care. Purified exosome product was discovered and manufactured at Mayo Clinic in the Mayo Clinic Van Cleve Cardiac Regenerative Medicine Program.

Next steps

This research will need additional studies to verify the findings. The next step is to test purified exosome product on rotator cuff injuries in large animal models. If the results are replicated, researchers plan to begin testing this procedure in early human clinical trials. The time frame is uncertain, but they hope it would be within the next few years.

This study was funded by the National Institutes of Health (Grants AR 738111 and AR 57745) and the Mayo Clinic Department of Orthopedic Surgery with support from Mayo Clinic Center for Regenerative Medicine.


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