Ultrasound combined with SDF-1α chemotactic microbubbles promotes stem cell homing in an osteoarthritis model

Osteoarthritis (OA) is a common joint disease in the middle and old age group with obvious cartilage damage, and the regeneration of cartilage is the key to alleviating or treating OA. In stem cell therapy, bone marrow stem cell (BMSC) has been confirmed to have cartilage regeneration ability. However, the role of stem cells in promoting articular cartilage regeneration is severely limited by their low homing rate. Stromal cell-derived factor-1α (SDF-1α) plays a vital role in MSC migration and involves activation, mobilization, homing and retention. So, we aim to develop SDF-1α-loaded microbubbles MB(SDF-1α), and to verify the migration of BMSCs with the effect of ultrasound combined with MB(SDF-1α) in vitro and in vivo. The characteristics of microbubbles and the content of SDF-1α were examined in vitro. To evaluate the effect of ultrasound combined with chemotactic microbubbles on stem cell migration, BMSCs were injected locally and intravenously into the knee joint of the OA model, and the markers of BMSCs in the cartilage were detected. We successfully prepared MB(SDF-1α) through covalent bonding with impressive SDF-1α loading efficacy loading content. In vitro study, ultrasound combined with MB(SDF-1α) group can promote more stem cell migration with highest migrating cell counts, good cell viability and highest CXCR4 expression. In vivo experiment, more BMSCs surface markers presented in the ultrasound combined with MB(SDF-1α) group with or without exogenous BMSCs administration. Hence, ultrasound combined with MB(SDF-1α) could promote the homing of BMSCs to cartilage and provide a novel promising therapeutic approach for OA.