Objective: This study aimed to investigate effects of TGF-beta 1-containing exosomes derived from bone marrow mesenchymal stem cells (BMSC) on cell function of rotator cuff tenocytes and its implication to rotator cuff tear. Methods: The primary BMSC and rotator cuff tenocytes were extracted and cultured. Identification of BMSC were performed by observing cell morphology and measurement of surface biomarkers by flow cytometry. BMSC-derived exosomes were extracted and identified by using electron microscopy, nanoparticle-tracking analysis (NTA) and western blotting. Cell proliferation and cell cycle were measured by CCK-8 assay and flow cytometry assay, respectively. Transwell assay was used for detection of tenocytes migration. The fibrotic activity of tenocytes was determined via qPCR and western blotting assays. Results: BMSC and BMSC-derived exosomes were successfully extracted. Treatment of BMSC-derived exosomes or TGF-beta 1 promoted cell proliferation, migration and increased cell ratio of (S + G2/M) phases in tenocytes, as well as enhanced the expression levels of fibrotic activity associated proteins. However, inhibition of TGF-beta 1 by transfection of sh-TGF-beta 1 or treatment of TGF beta R I/11 inhibitor partially reversed the impact of BMSC-derived exosomes on tenocytes function. Conclusion: Taken together, TGF-beta 1-containing exosomes derived from BMSC promoted proliferation, migration and fibrotic activity in rotator cuff tenocytes, providing a new direction for treatment of rotator cuff tendon healing. (C) 2020, The Japanese Society for Regenerative Medicine. Production and hosting by Elsevier B.V.