Efficacy of mesenchymal stem cells in treating patients with osteoarthritis of the knee: A meta-analysis

To assess the clinical efficacy and safety of mesenchymal stem cell (MSC) treatment for osteoarthritis of the knee (KOA), a systematic electronic literature search was performed on PubMed, EMBASE, and Web of Science. Studies published in English from the earliest record to December 2014 were searched using keywords including cartilage defect, cartilage repair, osteoarthritis, KOA, stem cells, MSCs, and various sources such as bone marrow concentrate (BMC), adipose-derived, synovial-derived, and peripheral blood-derived mesenchymal stem cells.

Methodology and Study Selection

The effect sizes of selected studies were determined by extracting pain scores from the visual analog scale (VAS) and functional changes from the International Knee Documentation Committee, Lysholm, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). These metrics were evaluated before and after MSCs or reference treatments at intervals of 3, 6, 12, and 24 months. Outcomes were modified after comparing the MSC group pooled values with the pretreatment baseline or between different treatment arms.

A systematic search identified 18 clinical trials on this topic, involving a total of 565 patients with KOA. The study composition included:

• 10 single-arm prospective studies
• Four quasi-experimental studies
• Four randomized controlled trials (RCTs) using BMCs

Clinical Outcomes and Efficacy

MSC treatment in patients with KOA showed continual efficacy for 24 months compared with their pretreatment condition. Effectiveness of MSCs was significantly improved at 12 and 24 months post-treatment, compared with the results observed at 3 and 6 months. Notably, no dose-responsive association in the MSC numbers was demonstrated during the analysis.

Improved outcomes were specifically achieved by patients who underwent arthroscopic debridement, used an activation agent, or presented with lower degrees of the Kellgren-Lawrence grade. Overall, MSC application ameliorated patient outcomes, specifically regarding pain relief and functional improvement from basal evaluations, peaking at the 12 and 24-month follow-up marks.