Emerging evidence showed that cardiac proliferation played a significant role in the cardiac rehabilitation and repair. Extracellular vesicles (EVs) are known to regulate multiple cell functions, whereas the role of EVs in cardiac proliferation still remains unclear. In this study, we found that serum EVs promoted cell proliferation in rat heart myoblastic H9C2 cells with significantly increased expression level of miR-17-3p. Inhibition of miR-17-3p could decrease H9C2 cells proliferation induced by serum EVs. Additionally, we found that TIMP3 was a target of miR-17-3p in H9C2 cells proliferation and the expression of TIMP3 was downregulated by serum EVs. Meanwhile, inhibition of TIMP3 increased cardiac proliferation. In conclusion, results of our study indicated that serum EVs could promote the proliferation of H9C2 cells via regulating miR-17-3p/TIMP3, which may be a potential therapeutic target for treatment of cardiac injury. (C) 2018 Elsevier Inc. All rights reserved.