In a recent preliminary study, scientists used stem cells to ease osteoarthritis. Although the trial was small scale, the results are promising and will pave the way for larger studies.

Osteoarthritis of the knee (KOA) occurs when the cartilage—the joint's natural cushioning system—breaks down in the knee. Without this buffer, bones can come into contact with each other, causing pain, stiffness, and a loss of flexibility.

According to the Centers for Disease Control and Prevention (CDC), osteoarthritis affects an estimated 30 million people in the United States. Osteoarthritis is predominantly a disease of older age, affecting more than 1 in 10 people over the age of 60. As the population of the United States is slowly aging, the number of people with osteoarthritis is likely to increase steadily.

Although physical interventions and medications can ease symptoms, there is currently no cure because it is not possible to regrow cartilage. Once KOA has progressed to the end stages, the only option is surgical replacement of the joint.

Stem cells and osteoarthritis

Recently, a group of researchers from the Krembil Research Institute, University Health Network in Toronto, Canada, looked into the potential use of stem cells to treat KOA. They published their results in the journal STEM CELLS Translational Medicine.

The scientists wanted to know whether it might be possible to regenerate knee cartilage using mesenchymal stromal cells (MSCs). These cells can develop into a number of different cell types, including muscle, bone, and, importantly, cartilage.

In all, the team recruited 12 participants with moderate-to-severe KOA and extracted MSCs from each person's bone marrow. In this pilot study, one of the main aims was to understand what constituted a safe and viable dosage, so the researchers injected each participant with one of three different doses of MSCs.

Over the next 12 months, the scientists followed the participants, assessing their progress using a battery of tests. For instance, they measured the levels of inflammatory biomarkers and the rate of cartilage breakdown, and they took regular magnetic resonance imaging (MRI) scans of the affected joints. They also asked the individuals to rate how well they felt they were doing.

By the end of the year-long study, the team found that there was a significant reduction in pain and an increase in self-reported quality of life. The participants tolerated all three doses well, and there were no serious adverse events. Those who received the highest doses experienced the most positive results. There was a significant reduction in inflammation within the knee joints of the participants, which is important because experts now consider inflammation to be an important driver of osteoarthritis. The authors write, "Pro-inflammatory monocytes/macrophages and interleukin 12 levels decreased in the synovial fluid after MSC injection." In fact, the authors believe that much of the pain relief might be due to this anti-inflammatory response.

Shortfalls and next steps

As they were carrying out a pilot study, the scientists only recruited a small group of participants. Researchers will need to carry out much larger trials before it is possible to use the technique in real-world patients. It is also worth noting that although the intervention reduced pain and inflammation, the scientists did not detect any cartilage regrowth, which some earlier trials have reported. This finding, the authors believe, might be because the trial only included participants with end-stage osteoarthritis. They suggest that "such regenerative effects are more likely to be observed in earlier-stage [osteoarthritis]." Also, the pilot study was open-label, meaning that both the researchers and the participants knew who was receiving which dosage. However, reservations aside, the investigators did not design the study to offer conclusive evidence that the method is effective. Instead, it acts as a stepping stone toward future endeavors.

This is not the first time that researchers have pitted stem cells against osteoarthritis. For instance, the authors of a 2015 study involving 30 participants concluded that "MSC therapy may be a valid alternative for the treatment of chronic knee osteoarthritis." A 2016 study with 60 participants reached similar conclusions.

"This clinical pilot study advances the field of stem cell research for patients with arthritis, showing safety and giving insights into potential therapy efficacy guidelines. We look forward to larger scale trial results."

—Dr. Anthony Atala, editor-in-chief of STEM CELLS Translational Medicine

If more extensive projects can replicate the benefits that these small-scale preliminary studies have revealed, stem cells could become the future of osteoarthritis treatment.