The Future of Joint Repair

Regenerative medicine is an umbrella term for a branch of medicine that uses stem cells and tissue engineering to “fix” tissues that have failed to repair themselves.

But expectations for regenerative medicine have sometimes gotten ahead of the science. Although its potential to repair and rebuild cartilage has not been fulfilled yet, it has had successes, especially for pain relief.

This booming field has been largely unregulated. So it’s important to separate what goes on in reputable research institutions from certain for-profit clinics that hawk therapies of questionable value.

Regenerative medicine – which is being tried primarily in osteoarthritis (OA) -- has two branches. One is tissue engineering, which tries to create replacements for damaged tissue. The other is self-healing, which uses injections of stem cells or blood products to push the body to repair itself.

Platelet-rich plasma (PRP) is probably most widely performed of these procedures. Blood is drawn from the patient and spun in a centrifuge to separate the platelets from other blood components. The platelets are then injected into problem areas.

How it Works: Your body’s first response to injury is to send platelets to the site. This blood component contains growth factors and other nutrients. PRP is thought to boost that natural response.

Benefits: PRP is done fairly quickly and generally requires only one injection. It provides symptomatic relief that may last three to six months. In some studies, PRP outperformed and sometimes outlasted hyaluronic acid or corticosteroid injections. “But does it have a benefit that goes beyond pain relief? We just don’t know,” says Christopher Evans, PhD, director of Mayo Clinic’s Musculoskeletal Gene Therapy Research Lab.

Keep in mind: Studies suggest the preparation method, the type of centrifuge used and even the delivery method can significantly affect the results. Most insurers don’t cover PRP; out-of-pocket costs can range from $500 to $2,000.

Called Orthokine in Europe and Regenokine in the United States, ACS uses the patient’s own blood to fight pain. Your blood is processed to increase the anti-inflammatory proteins and growth factors it contains. Then it is injected in your affected joints, usually in a series of shots.

How it works: Regenokine blocks interleukin-1 (IL-1), a key player in inflammation. It relieves pain and could conceivably slow OA damage.

Benefits: Dr. Evans says the treatment is safe and well-tolerated. Like PRP, studies show only symptom relief, but no evidence of any tissue regrowth.

Keep in mind: ACS is more commonly used for muscle, tendon and ligament damage than it is for arthritis. It is more complex and less readily available than PRP and the cost may be as high as $10,000 a session.

Stem cells can make copies of themselves and turn into other types of cells. In adults, a small number of these unspecialized cells lie dormant in many organs and tissues. The idea that stem cells might be a source of renewable tissue for almost any part of the body is the basis for this line of treatments.

How it works: Mesenchymal stem cells (MSCs), which are found mainly in bone marrow and fat, are usually used for these procedures. The stem cells are separated from other tissue components and are then injected into your painful joint. The theory is that the stem cells will initiate tissue regeneration in the joint.

Benefits: MSCs stimulate the production of anti-inflammatory proteins and growth factors. There is evidence – from studies of varying quality – that MSCs are safe and can improve pain and function in arthritic joints.

Riley Williams III, MD, who directs the Institute for Cartilage Repair at the Hospital for Special Surgery (HSS) in New York City says, “I’m really excited about the prospects for treating very early arthritis and some chronic overuse injuries. [Stem cells] are not going to work for bone-on-bone arthritis, but they are helpful when people are just starting to have some pain and swelling.”

Keep in mind: There’s no evidence that stem cells can restore lost tissue or cause cartilage to grow.

“The number of true stem cells in bone marrow and fat is vanishingly small,” explains Brian Halpern, MD, a sports medicine specialist at HSS. “If we could take the bone marrow to the lab and isolate the small population of stem cells and expand them in culture – then we’d really have something,” he says. But the FDA prohibits that in the US at this time.  It’s done in much of the rest of the world, however.

Most insurers won’t pay for stem cell therapies. The price of a single knee injection at direct-to-consumer stem cell clinics is around $5,100.

When small holes or tears develop in cartilage, usually as a result of injury, they can leave areas of bare bone. Over time, these can lead to OA. Filling them with repair tissue can relieve pain, improve function and delay or prevent the need for surgery later on. A few different techniques are available.

How it works: Microfracture involves drilling tiny holes in the bony layer under the defect, where a blood clot forms and eventually fibrocartilage grows. Fibrocartilage isn’t as strong or durable as the cartilage we were born with (called hyaline cartilage).

In cartilage transplantation, a plug of cartilage and bone is taken either from a healthy part of your knee or from a donated source at a tissue bank. The plug is then transplanted into the cartilage defect.

Matrix-associated autologous chondrocyte implantation (MACI) involves removing a small piece of cartilage from a non-weight-bearing part of the knee. It’s sent to a lab where the cartilage cells are grown on a membrane. The resulting membrane sheet can be cut to fit the defect. Two similar procedures – NeoCart and Novocart 3D – are in clinical trials and likely to be approved within the next few years.

Benefits: Most cartilage transplants are successful, and 88 percent of patients return to sport. Allograft and autograft transplants are becoming primary treatment strategies, particularly for younger athletes and active people.

Studies show that about 85 percent of MACI implants survive and integrate with existing cartilage.

Keep in mind: None of these cartilage restoration techniques are intended for people with widespread damage from arthritis.

In-network cost for a single-knee allograft is about $14,000 and autografts are about $11,000. Current pharmacy prices for MACI are around $40,000; the other two will be priced after they receive FDA approval.

Stem cells wrapped in cartilage: Jeffrey Lotz, PhD, director of the Orthopaedic Bioengineering Laboratory at the University of California, San Francisco, wrapped MSCs in a sheath of cartilage cells that signal the MSCs to become cartilage. It’s worked in animal models of arthritis; whether it will work in other larger animal models and humans remains to be seen.

Hydrogel scaffolds: Jennifer Elisseeff, PhD, director of the Translational Tissue Engineering Program at Johns Hopkins University invented a scaffold to help repair cartilage defects. The gel starts out soft, smooth and watery, and cartilage cells grow in it. In a small clinical trial, the gel, injected into a defect after microfracture, significantly improved results of the procedure. Patients formed less scar tissue and more “normal” cartilage. Elisseeff also invented an adhesive that bonds to the hydrogel and cartilage, which helps new cells to integrate with existing tissue.

Anti-inflammatory solutions: Farshid Guilak, PhD, co-director of the Washington University Center of Regenerative Medicine in St. Louis, Missouri (and an Arthritis Foundation-funded researcher), is working on anti-inflammatory solutions that include purified stem cell injections and a combination of gene therapy and tissue engineering to improve the body’s repair mechanisms.

Personal Communications:

Jennifer Elisseeff, PhD,  Cell and Tissue Engineering Program, Johns Hopkins University

Christopher Evans, PhD, Musculoskeletal Gene Therapy Research, Mayo Clinic

Farshid Guilak, PhD,  Washington University Medical Center in St. Louis

Brian Halpern, MD, Hospital for Special Surgery

Wellington Hsu, MD, Northwestern University Feinberg School of Medicine

Jeffrey Lotz, PhD, Orthopaedic Bioengineering Laboratory, University of California, San Francisco

Nicolas Piuzzi, MD, Cleveland Clinic

Riley Williams, III, MD, Institute for Cartilage Repair, Hospital for Special Surgery