Injectable allogeneic bone mesenchymal stem cells: a potential minimally invasive therapy for atrophic nonunion.

How to enhance atrophic nonunion repairing is a common challenge encountered in orthopaedic surgeons. With the increasing popularity of minimally invasive techniques, one of the major thrusts in treatment approaches for atrophic nonunions is to develop injectable systems that can shorten the surgical operation time, reduce the morbidity and costs for patients. Bone mesenchymal stem cells (BMSCs) may provide new strategies to treat atrophic nonunion because of their prolonged self-renewal capacity and ability to differentiate into osteogenic lineage under the proper conditions. However, providing an autologous BMSCs in the clinical setting is often limited, because the patient’s marrow is damaged or the cell yield from healthy marrow is reduced. Due to the limitation of autologous BMSCs in clinical application, we turn to consider allogeneic BMSCs as seeding cells in atrophic nonunion repair. Allogeneic BMSCs could are isolated from one or more donors would have the potential to be expanded and cryopreserved for future use. Previous studies have indicated that BMSCs possess immune-privileged properties, which avoid or actively suppress the immunological responses. Here we propose the hypothesis that the application of osteo-induced allogeneic BMSCs in fibrin gels for delivery of the cells by means of an injectable device would enhance repair of atrophic nonunion without the use of immunosuppressive therapy. Furthermore, fibrin gel could be useful as BMSCs carrier to deliver cells in vivo, there is no immunogenicity to be expected and BMSCs were able to spread and proliferate into the fibrin. Therefore, if the hypothesis is proved to be practical, it might represent a novel minimally invasive therapeutic approach and enhance atrophic nonunion repairing.