Using Stem Cells to Cure Arthritis and Cartilage Damage

Can advances in science make this a possible option?

Stem cell research
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Every day I see patients who are fighting the battle against time and aging. We want to keep active and healthy, and most importantly, free of pain. We want to continue to do the things that we love to do, many of which require healthy joints, yet we are fighting against the damage and deterioration of the cartilage in our joints.

All around us, we see examples of people who do extraordinary activities until the late stage of life.

We see people running marathons, or walking the golf course, yet our joints will not let us keep up. I also see many younger and middle-aged athletes who sustain damage to their joints, and worry about the long-term implications of this damage and if it means their ability to continue these activities is limited. 

The question that comes up is: what can we do? Cartilage is limited in its ability to heal or regenerate, but we need it for longer than it is lasting. Can we do anything to stimulate the healing of cartilage, or to regrow a new layer of cushioning for our joints? Are stem cells the answer to reversing the course of an aging or damaged joint?

What Is Cartilage and How Does It Get Damaged?

Cartilage is a type of connective tissue in the body. In our joints, we have a few types of cartilage, but most often people refer to the smooth lining of a joint called articular or hyaline cartilage.

This type of cartilage forms a smooth layer of cushion on the end of a bone at the joint. This tissue is very strong, yet it has the ability to compress and absorb energy. It is also very smooth and slippery and allows a joint to glide effortlessly through a broad range of motion.

When joint cartilage is damaged, this smooth cushioning layer can be worn away.

In the case of traumatic injuries, sometimes a sudden force causes the cartilage to break off or be damaged, exposing the underlying bone. In the case of osteoarthritis (also called degenerative or wear-and-tear arthritis), over time that smooth layer can wear thin and uneven. Eventually, as that cushion wears away, joint movements can become stiff and painful. Joints can become inflamed and swollen. And as these symptoms worsen, typically pain and limitations in activity become problematic.

There are treatments for cartilage damage and arthritis, but typically these treatments are focused either on relieving symptoms by smoothing down the damaged cartilage, or replacing the joint surface with an artificial implant, such as with knee replacement or hip replacement surgery.

How Can Stem Cells Help Cure Damaged Cartilage?

Stem cells are special cells that have the ability to multiply and develop into different types of tissue. In the developmental stages of a fetus, stem cells are plentiful.

However, in adulthood, stem cells are restricted to specific tasks of regenerating a few types of cells, such as blood cells. There are not normally stem cells found in cartilage tissue, and therefore there is little capacity to heal or regrow new cartilage.

Most often in the setting of orthopedic surgery and joint problems, stem cells are obtained from adult stem cell sources. The primary sources are bone marrow and fatty tissue. These stem cells have the ability to develop into cartilage cells, called chondrocytes. They also exhibit some other helpful qualities by stimulating the body to reduce inflammation, stimulate cell repair, and improve blood flow. This process is caused by the secretion of cellular signals and growth factors to stimulate the body to initiate healing processes.

Once stem cells have been obtained, they need to be delivered to the area of cartilage damage. One option is to simply inject the stem cells into the joint. There have been a number of studies investigating just this, and some data shows improvement in symptoms. How much of this improvement is the result of new cartilage growth versus other effects of stem cells (the healing properties listed above, including the anti-inflammatory effects) is unknown.

The problem with just injecting stem cells is that cartilage is a complex tissue that is comprised of more than just cells. In order to regenerate cartilage, the complex tissue structure of cartilage must also be reconstructed. Cartilage is often described as having a scaffold-like structure that is composed of collagen, proteoglycans, water, and cells. Injecting just the stem cells is thought to be ineffective in stimulating the formation of the entire cartilage structure.

There are investigations on types of 3-dimensional tissue scaffolds engineered to have a cartilage-like structure. The stem cells can then be injected into the scaffold, in hopes of better restoring a normal type of cartilage. Three-dimensional printing is quickly becoming an exciting part of this type of research.

Do Stem Cell Treatments Work Long-Term?

There have been a number of studies into the use of stem cells for the treatment of cartilage damage and arthritis. Most of these studies involve the knee joint, but there are also studies looking at the ankle, shoulder, and other joints too. Most of these studies use injections, as tissue-engineered scaffolds are still being developed and are not well researched.

On a positive note, these studies have often shown improvement in symptoms, with less pain and improved functional scores. On the down side, most of these studies were very small and lasted only months or years. The long-term implications of stem cell injections have not been investigated.

This isn't because no one is looking into these issues, but rather because the gathering of long-term data takes a long time. Therefore, we are probably a decade or more away from knowing too much about how this impacts the long-term health of a joint.

The other big problem with most of these studies is that they haven't been shown to be much, if any, better than standard non-surgical arthritis treatments. So while people may have some improvement with stem cells, this may not be all that different than with other treatments considered safer and much less costly. For example, if a cortisone shot or physical therapy has beneficial effects, then why inject an experimental treatment which hasn't been shown to be much better?

Finally, there are serious questions about the safety of stem cell treatments. There have been questions ranging from immune system activation to malignant transformation. Part of the problem is that some types of stem cell treatments are probably very safe, while others impart significant risk, yet all are categorized as "stem cell treatments."

It can be hard for patients to know how safe the treatment they are receiving might be. Until we have developed a common language around the use of stem cells, and understand the risks and benefits of different types of stem cell treatments, it is too soon for these experimental treatments to be broadly recommended.

Is It Worth Waiting?

One of the most common questions I hear from people considering next steps in arthritis treatment is whether it is worth the wait for stem cell treatments: should I put off a joint replacement in hopes that stem cells are around the corner?

This is unlikely. Probably stem cells will be most useful initially for people who have an injury to their joint, and want to prevent the deterioration of cartilage in that joint, not for people wanting to regrow new cartilage. For example, a young athlete with a normal knee sustains a ligament injury and associated cartilage damage. The structure of their knee is normal, but the cartilage was damaged. The hope is that injecting stem cells may help stimulate the body to repair that damage before the cartilage is irreparably harmed.

This is a far different scenario from someone who has a badly damaged joint that is out of alignment, lacks cartilage, and has developed deformities such as bone spurs. In these scenarios, the likelihood of stem cells helping significantly anytime in the near future is slim. We still have a long way to go in terms of tissue engineering and stem cell delivery to know how to help these individuals.

Bottom Line

Stem cells are considered by many to be the future of orthopedics and joint healing. We are just starting to learn how to harness the abilities of a stem cell to repair and regrow cartilage. While there is encouraging research, we are likely decades away from being able to reverse the effects of arthritis and cartilage damage in a way that will benefit most people.

At present, there is much left to learn about stem cells. We simply do not know enough about the risks of treatment, the possible benefits, and if they offer any advantage over other treatments currently used in the management of cartilage problems in our joints. Right now, what one person refers to as "stem cell treatment" may be completely different from another. Therefore, comparing treatments, safety, and effectiveness is very difficult.

I would recommend significant caution with someone who promises improvement with treatment using stem cells. Most importantly, current stem cell treatment of cartilage problems has not been shown to reverse the effects of arthritis. While some studies show some clinical improvement, this is nowhere near a cure for the condition.

Sources:

LaPrade RF, Dragoo JL, Koh JL, Murray IR, Geeslin AG, Chu CR. "AAOS Research Symposium Updates and Consensus: Biologic Treatment of Orthopaedic Injuries" J Am Acad Orthop Surg. 2016 Jul;24(7):e62-78.

Tuan RS, Chen AF, Klatt BA. "Cartilage regeneration" J Am Acad Orthop Surg. 2013 May;21(5):303-11.

Saltzman BM, Kuhns BD, Weber AE, Yanke A, Nho SJ. "Stem Cells in Orthopedics: A Comprehensive Guide for the General Orthopedist" Am J Orthop. 2016 July;45(5):280-288, 326.

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