Magnetic targeting of autologous bone marrow–derived mesenchymal stromal cells for knee osteoarthritis: a first-in-human exploratory study

Abstract Knee osteoarthritis lacks disease-modifying therapies, and poor retention of intra-articularly injected mesenchymal stromal cells at cartilage lesions may limit their therapeutic potential. We conducted a physician-initiated, single-center, open-label, first-in-human exploratory trial to assess the safety and feasibility of magnetic targeting–guided delivery of autologous bone marrow–derived mesenchymal stromal cells in symptomatic knee osteoarthritis. Five female patients with Kellgren–Lawrence grade 3 osteoarthritis underwent arthroscopic microfracture in areas of full-thickness cartilage loss, followed by intra-articular injection of magnetically labeled autologous bone marrow–derived mesenchymal stromal cells under a ring-shaped electromagnetic device. All patients completed 48 weeks of follow-up. No serious adverse events, tumor formation, abnormal tissue proliferation, or device-related complications were observed. Knee joint effusion was the only adverse event considered potentially related to the investigational cell therapy and resolved without additional treatment. Clinical outcomes showed exploratory improvement trends, including an increase in the mean Knee injury and Osteoarthritis Outcome Score Quality of Life from 15.0 to 50.0 at 48 weeks. Magnetic resonance imaging showed variable structural changes, whereas second-look arthroscopy demonstrated cartilage-like repair tissue in evaluated cases. These findings indicate that magnetic targeting–guided delivery is a feasible cell-delivery strategy for knee osteoarthritis, with no major safety concerns and exploratory signals of therapeutic potential.