Stem Cell Therapy for Knee Osteoarthritis Shows Variable Results, finds study

Knee osteoarthritis (KOA) affects more than 1 in 10 people over 40 years of age, impairing patients' mobility and quality of life. With limited treatment options, stem cell injections have been promoted as a treatment option, but evidence of efficacy from clinical trials or claims from clinics selling untested options often lacking. Even where well-designed clinical trials were performed, there was no clear consensus about the benefit of stem cell injections for KOA, likely due to the many variables at play.

A major source of variability comes from the cells used for injections. Mesenchymal stromal cells (MSCs), which can be isolated from e.g. fat or bone marrow, are frequently used to treat KOA in clinical studies. Using a patient's own cells reduces the risk of an immune response and any inadvertent transmission of pathogens but the quality and the therapeutic potential of MSCs varies between patients, contributing to heterogeneous treatment outcomes. Predicting MSC potency could be a powerful tool to achieve more consistent therapeutic in such therapeutic settings.

To tackle the issue of MSC treatment heterogeneity, Sowmya Viswanathan from the Schroeder Arthritis Institute, University Health Institute, Canada, along with colleagues performed a long-term follow-up to a Health Canada-authorized phase I/IIa clinical trial (NCT02351011) with KOA patients receiving MSC injections, whereby the MSCs were derived from the patients’ own bone marrow. The work was published today in Stem Cell Reports.

Over the course of 24 months, the patients’ self-reported pain and mobility scores were used to classify the patients as responders versus non-responders. Patients reporting at least 20% improvement in both pain and knee mobility were classified as responders, while non-responders showed no signs of improvement or became worse in pain or mobility scores. At 12 months post-injection follow-up, six out of twelve patients were responders, which in the majority of patients held up at 24 months post-injection.

To test if certain MSC features correlated with therapy outcomes and to find a potential way for predicting MSC potency, Viswanathan’s team then ran a panel of lab-based tests on the MSCs from all 12 patients and found some differences between the MSCs from responders compared to non-responder. MSCs from responders had a greater anti-inflammatory effect and dampened immune cell reactivity more effectively than MSCs from non-responders. Furthermore, the researchers identified 14 microRNAs, short RNAs regulating gene expression in cells, present in different quantities in responder versus non-responder MSCs. By contrast, baseline values for disease severity and inflammation did not correlate with therapy response.

This study suggests that lab-based tests on cultured MSCs may be predictive of MSC potency, so that ultimately only MSCs with an enhanced therapeutic potential can be pre-selected for clinical application in KOA patients. Importantly, follow-up controlled clinical studies with larger patient cohorts will be required to corroborate those findings.

Reference:

Robb K, Rabani R, Vohra S ... Responders vs. non-responders to mesenchymal stromal cells in knee osteoarthritis: Mechanistic correlates of donor cell and patient features Stem Cell Reports,DOI: 10.1016/j.stemcr.2026.103024