Effect of Exosomes From Bone Marrow-Derived Mesenchymal Stromal Cells and Adipose-Derived Stromal Cells on Bone-Tendon Healing in a Murine Rotator Cuff Injury Model.

Background: Bone-tendon injury is characterized by poor self-healing. It is established that exosomes are favorable for tissue repair and regeneration. However, their effect on bone-tendon healing has not yet been determined. Purpose: To compare the effectiveness of exosomes derived from adipose-derived mesenchymal stromal cells (ADSC-Exos) and bone marrow-derived mesenchymal stromal cells (BMSC-Exos) on bone-tendon interface healing in murine rotator cuff injury model and explore the underlying mechanisms thereof. Study Design: Controlled laboratory study. Methods: A total of 63 male C57BL6 mice with rotator cuff injuries underwent surgery and were randomly assigned to a control group treated without exosomes (n = 21), an ADSC-Exos group (n = 21), or a BMSC-Exos group (n = 21). The mice were sacrificed 4 or 8 weeks after surgery, and tissues were collected for histologic examination and radiographic and biomechanical testing. For exosome tracing in vivo, mice were sacrificed 7 days after surgery. A series of functional assays (radiographic evaluation, proliferation assay, Alizarin Red staining, alkaline phosphatase staining and activity, Alcian blue staining, quantitative polymerase chain reaction analyses, and glycosaminoglycans quantification) were conducted to evaluate the effect of exosomes on the cellular behaviors of the BMSCs in vitro. A statistical analysis of multiple-group comparisons was performed by 1-way analysis of variance, followed by the Bonferroni post hoc test to assess the differences between the 2 groups. Results: The ADSCs and BMSCs were positive for surface markers CD29 and CD90 and negative for surface markers CD34 and CD45 and could differentiate into osteoblasts, chondrocytes, and adipocytes. Exosomes showed a cup- or sphere-shaped morphology and were positive for CD63 and TGS101. Local injection of ADSC-Exos and BMSC-Exos could recruit BMSCs and promote osteogenesis, chondrogenesis, and bone-tendon healing. In vitro, ADSC-Exos and BMSC-Exos could significantly promote the proliferation, migration, osteogenic differentiation, and chondrogenic differentiation ability of BMSCs. In vivo, ADSC-Exos and BMSC-Exos significantly accelerated bone-tendon injury healing, with no significant statistical difference between them. Conclusion: ADSC-Exos and BMSC-Exos exhibited similar therapeutic effects on bone-tendon healing in our murine animal model. Clinical Relevance: ADSC-Exos and BMSC-Exos may be used to develop a new cell-free therapy method for promoting rotator cuff injury repair.