Abstract
PURPOSE: Implantation of mesenchymal stem cells (MSCs) is a potential non-surgical option for cartilage repair. Currently, its clinical use largely focuses on focal cartilage defect repair and intra-articular injections in knee osteoarthritis (OA). Most studies have looked at the efficacy of MSCs from autologous sources, which can be limited by inter-patient variability of age, diseases, sites and methods of harvest. This systematic review aims to evaluate studies that focus on allogeneic MSCs implantation versus placebo in patients with knee OA to summarise the efficacy and safety of allogeneic MSCs in knee OA. METHODS: A systematic search following PRISMA guidelines was performed in PubMed, Scopus and EMBASE. Original studies investigating the outcomes of allogeneic MSC implantations in patients with knee OA were included. Data on clinical outcomes, such as subjective scores such as VAS and WOMAC, radiological outcomes, such as cartilage thickness, and histological outcomes, such as ICRSII score, were extracted. RESULTS: Seven studies were included in this review. There was 30.4 points improvement in Visual Analogue Scale scores and 40.0 points of improvement in Western Ontario and McMaster Universities Osteoarthritis Index scores at 12 months. Improved cartilage thickness and decreased poor cartilage quality as measured by T2 relaxation. Measurements at the lesion site were observed in three studies as assessed by postoperative magnetic resonance imaging and this was correlated clinically. One study also showed histological improvement with overall ICRSII scores significantly improving from 32.0 ± 21.6 at baseline to 55.9 ± 23.2 at 6 months (p < 0.05). No major complications or tumorigenesis occurred. CONCLUSION: Allogeneic MSC implantation in patients with knee osteoarthritis provides sustained clinical improvement and satisfactory cartilage restoration, up to 12 months follow-up. These results are supported by both imaging and histological studies. The safety profile of allogeneic MSCs is excellent, with minimal adverse events mainly limited to local reaction to injection and no long-term adverse effects. LEVEL OF EVIDENCE: Level II.