Exosomal miRNA-21-5p derived from bone marrow mesenchymal stem cells promote osteosarcoma cell proliferation and invasion by targeting PIK3R1

Mesenchymal stem cells (MSCs) are a class of pluripotent cells that can release a large number of exosomes which act as paracrine mediators in tumor associated microenvironment. However, the role of MSC-derived exosomes in pathogenesis and progression of cancer cells especially osteosarcoma has not yet been thoroughly clarified until now. In this study, we established a co-culture model for human bone marrow derived MSCs with osteosarcoma U2OS and MG63 cells, then extraction of exosomes from induced MSCs and study the role of MSC-derived exosomes in the progression of osteosarcoma cell. It was the aim of this study to address potential cell biological effects between MSCs and osteosarcoma cell. we found that MSC-derived exosomes can significantly promote osteosarcoma cells proliferation and invasion. we also found that miR-21-5p were significantly overexpressed in human bone marrow MSCs and MSC-derived exosomes compared with that of human fetal osteoblastic cell line hFOB1.19 by using quantitative realtime polymerase chain reaction (qRT-PCR). Proliferation and invasion of osteosarcoma cells U2OS and MG63 were significantly enhanced by MSC-derived exosomes that were transfected with miR-21-5p. Bioinformatics analysis and dual‐luciferase reporter gene assays validated the targeted relationship between exosomal miR‐21-5p and PIK3R1. Furthermore, we demonstrated that miR-21-5p-abundant exosomes derived human bone marrow MSCs could activate PI3K/Akt/mTOR pathway by suppressing PIK3R1 expression in osteosarcoma cells U2OS and MG63. In conclusion, Our findings provide new insight into the interaction between MSCs and osteosarcoma cells in tumor associated microenvironment. Notably, the use of a miR-21-5p inhibitor has an excellent restraining effect on osteosarcoma proliferation and invasion, which provides therapeutic potential for osteosarcoma in future clinical medicine.

Immunosupressive Property of Mesenchymal Stem Cells (MSCs) in Mixed Lymphocyte Reactions In Vitro.

Meesnchymal stem cells (MSCs) were successfully used in the prevention and treatment of graft versus host disease (GVHD) after allogeneic hematopoietic stem cell transplantation. To further explore the immunosuppressive property of human bone marrow (MSCs) in alloantigen-induced mixed lymphocyte reactions (MLRs) in vitro, human bone marrow MSCs and lymphocytes were prepared from healthy volunteers. MSCs were expanded in vitro in Mesencult serum free media. MSCs were cocultured with one-way MLRs and bidirectional MLRs, responder cells were labeled with carboxyfluorescein diacetate- succinimidyl ester (CFSE) in bidirectional MLRs. Cell Counting Kit-8(CCK-8)kit was used in cell proliferation detection, T-cell subsets were analyzed by flow cytometry (FCM). The results showed that MSCs were positive for CD105, CD73, CD13, CD90 and were negative for hematopoietic cell markers. In one-way MLRs, MSCs down-regulated alloantigen-induced lymphocyte expansion in a dose-dependent and MHC-independend manner. In two-way MLRs, MSCs suppressed proliferation of CFSE positive cells. T cell subsets were changed: Th2 and Tc2 were down-regulated. Th2 was reduced from 1.70% to 0.65%, and Tc2 reduced from 1.10% to 0.47%, while Th1 and Tc1 were unaffected. T cells that became CD69+, which was an early activation marker, were significantly up-regulated from 7.14% to 26.12% and CD4+CD25+T regulatory cells (CD4+CD25+Tr) were up-regulated from 4.04% to 6.19%, which indicating that suppression did not interfere with activation phase of T cells and might be mediated by CD4+CD25+Tr partly. We conclede that MSCs down-regulated alloantigen-induced lymphocyte expansion. The immunosupressive effect might involve in post-activation phase of T cells. CD4+CD25+Tr might contribute to the suppressory activity of MSCs.