When a person tears his or her rotator cuff—the tendons and muscles that help stabilize and move the shoulder—surgery is often needed. Although techniques have improved considerably, torn tendons often heal poorly. To improve outcomes, Scott Rodeo, MD, Attending Orthopedic Surgeon, Co-Chief Emeritus of the Sports Medicine and Shoulder Service, is studying intrinsic stem cells, which are probably involved in early tissue formation, to find out if they can help heal injured tendons. Dr. Rodeo and his team of researchers are the first to use these cells in musculoskeletal tissue, so we asked him for the latest on this promising treatment, which is still in the early stages of research.
What are intrinsic stem cells and why are they important?
Dr. Rodeo: Stem cells can develop into many different cell types, such as those found in muscle, blood and the brain. In some parts of the body, like the bone marrow (the spongy center of certain bones), they divide to repair and replace damaged tissue. But there are few “true” stem cells based on formal criteria that define a stem cell, and our ability to use them is limited. So we decided to focus on the intrinsic population of stem cells found in tendons and the meniscus, the cartilage that cushions your thighbone and shinbone. These stem cells are tissue-specific, so the ones found in tendons, for instance, can only be used for tendon repair. We wanted to find out how to turn them on in order to promote healing in patients recovering from procedures like rotator cuff repair.
What have you discovered in your research so far?
Dr. Rodeo: We have found that when we stimulate intrinsic stem cells, new blood vessels form, cells proliferate and the tissue becomes stronger. In our studies, we performed mechanical testing of tendon strength, and it was significantly different from the tendons that were not treated with these cells. This is a completely novel approach to cell-based therapies.
Might stem cells one day be used as a treatment for other musculoskeletal injuries?
Dr. Rodeo: Yes, intrinsic stem cells may be able to play a role in meniscus repair.
What do you think the future might hold for this type of treatment?
Dr. Rodeo: We are exploring whether donor stem cells could be used to treat unrelated people with musculoskeletal injuries. Eventually, we may be able to develop an off-the-shelf source of these cells. In addition, we are starting to investigate a new, exciting approach to stem cell treatment. We will take a skin or blood cell and reprogram it with four specific genes that can make the cell function like an embryonic stem cell, which can turn into many different cell types. Research has shown that these cells, known as induced pluripotent stem cells (iPSCs), have tremendous potential for tissue regeneration. They may also carry fewer risks, since they can be taken from a patient’s own body as opposed to that of a donor. This reduces the chances of an immunologic reaction or transmission of infection or disease. Today, we are beginning to study these cells for tendon repair. This work will allow us to ultimately pursue U.S. Food & Drug Administration (FDA) clearance to begin a clinical trial in patients.
Dr. Scott Rodeo is an orthopedic surgeon and the co-chief emeritus of the Sports Medicine and Shoulder Service at Hospital for Special Surgery. He specializes in sports medicine injuries of the knee, shoulder, ankle, and elbow.
