BACKGROUND:Currently, what we know about exosomes is that it can be produced by a variety of cel s and transfer a variety of materials, producing subsequent function of regulation.
OBJECTIVE:To review the function of exosomes in mesenchymal stem cel differentiation, in order to provide reference for further in-depth study.
METHODS:With the key words of“exosome, mesenchymal stem cel , differentiation”in Chinese and English, respectively, a computer-based search was performed for articles published in CNKI, Medline and Embase databases from January 2001 to September 2016. After the initial screening, the reserved articles were further detailed, summarized and concluded.
RESULTS AND CONCLUSION:Exosomes are a kind of vesicles 40-100 nm in diameter, which can be secreted by a variety of cel types, containing functional products, such as functional protein, gene product, lipid and so on. As a bridge of adjacent cel s transferring functional products, exosomes are becoming an issue of concern in the microenvironment for cel interaction. In the differentiation of mesenchymal stem cel s, exosomes also play an indispensable role via pathway regulation.

BACKGROUND:There is no clear understanding about the effect of let-7f and interleukin-6 (IL-6) on the proliferation of bone marrow mesenchymal stem cels and their relationship.
OBJECTIVE: To explore the effects of expression levels of let-7f and IL-6 on the proliferation of bone marrow mesenchymal stem cels and their relationship.
METHODS:(1) LV-rno-let-7f-up and LV-rno-let-7f-down were constructed and transfected into bone marrow mesenchymal stem cels of Sprague-Dawley rats, respectively. Then, there were four groups in the study: transfection upregulation group transfected with LV-rno-let-7f-up), transfection inhibition group (transfected with LV-rno-let-7f-down), negative control group (transfected with FU-RNAi-NC-LV), and untransfected group. The expression level of let-7f in each group was detected by qRT-PCR. The proliferation ability of cels and expression levels of IL-6 when let-7f expression was at different levels were detected by MTT, flow cytometry and ELISA. The expression of Cyclin D1 at mRNA and protein levels was detected by qRT-PCR and western blot, respectively. (2) To predict the potential target gene of let-7f, the wild-type/mutant IL-6 3’UTR reporter gene vectors were constructed, and cotransfected with let-7f/let-7f inhibitor respectively into the 293T cels to measure the luciferase.
RESULTS AND CONCLUSION: Compared with the negative control group, the proliferative and cloning capacities of cels in the transfection upregulation group were higher; the number of cels was significantly decreased at G1 stage and increased at S stage, and the apoptotic cels were reduced in number (P < 0.05). However, the transfection inhibition group had opposite results. The expression level of IL-6 in the transfection upregulation group was lower than that in the untransfected group and negative control group (P < 0.05); while in the transfection inhibition group, the expression level of IL-6 was significantly increased (P < 0.05). The expression of Cyclin D1 at mRNA and protein levels was up-regulated in transfection upregulation group (P < 0.05) and down-regulated in the transfection inhibition group (P < 0.05), but there was no significant difference between the negative control group and untransfected group (P > 0.05). Luciferase activity of cels transfected with wide-type IL-6 3’UTR and let-7f was significantly reduced (P < 0.05). These findings indicate that up-regulation of let-7f can promote the proliferative and cloning capacities of bone marrow mesenchymal stem cels and reduce cel apoptosis, but downrelation of let-7f exhibits an inhibitory effect. Overexpression of IL-6 can suppress the proliferation of bone marrow mesenchymal stem cels, which is considered to be a target gene of let-7f, and let-7f may suppress the expression of IL-6 to promote the cel proliferation.