A novel cell delivery system using magnetically labeled mesenchymal stem cells and an external magnetic device for clinical cartilage repair

Purpose: The purpose of this study was to investigate whether it is possible to successfully accumulate magnetically labeled mesenchymal stem cells (MSCs), under the direction of an external magnetic force, to the desired portion of osteochondral defects of the patellae after intra-articular injection of the MSCs. Methods: MSCs were cultured from bone marrow and were labeled magnetically. Osteochondral defects were made in the center of rabbit and swine patellae, and magnetically labeled MSCs were injected into the knee joints either under the direction of an external magnetic force or with no magnetic force applied. In the rabbit model we evaluated the patellae macroscopically and histologically, and in the swine model we observed the patellae arthroscopically. Results: Accumulation of magnetically labeled MSCs to the osteochondral defect was shown macroscopically and histologically in the rabbit model and was shown by arthroscopic observation to be attached to the chondral defect in the swine model. Conclusions: We showed the ability to deliver magnetically labeled MSCs to a desired place in the knee joint. Clinical Relevance: Our novel approach is applicable for human cartilage defects and may open a new era of repairing cartilage defects caused by osteoarthritis or trauma by use of a less invasive technique.