Problem In mammals, implantation involves interactions between an activated blastocyst and a receptive endometrium. There are controversies on the role of microRNAs in preimplantation embryo development. The actions of endometrial microRNAs on implantation are beginning to be understood. Method of Study Review of literature on microRNAs in preimplantation embryos and endometrium. Results Emerging evidence suggests a role of microRNAs in blastocyst activation and implantation. Differential expression of microRNAs is found between receptive and non‐receptive endometria. Members of the let‐7, miR‐200, miR‐30 families, and the miR‐17‐92 clusters are more commonly found to be associated with endometrial receptivity. Experimental studies show that the targets of the differentially expressed microRNAs affect endometrial receptivity, decidualization, and embryo implantation. Free and exosome/microvesicle containing microRNAs have been detected in human and ovine uterine luminal fluid (ULF). They may serve as mediators of embryo–endometrium dialog. Some observations suggest that the microRNAs in ULF may be used as biomarkers in infertility treatment. Conclusion MicroRNAs in endometrium and blastocysts are involved in the implantation process.

Extracellular vesicles (EVs) are membrane-bound vesicles released by cells and act as media for transfer of proteins, small RNAs and mRNAs to distant sites. They can be isolated by different methods. However, the biological activities of the purified EVs have seldom been studied. In this study, we compared the use of ultracentrifugation (UC), ultra-filtration (UF), polymer-based precipitation (PBP), and PBP with size-based purification (PBP+SP) for isolation of EVs from human endometrial cells and mouse uterine luminal fluid (ULF). Electron microscopy revealed that the diameters of the isolated EVs were similar among the tested methods. UF recovered the highest number of EVs followed by PBP, while UC and PBP+SP were significantly less efficient (P<0.05). Based on the number of EVs-to-protein ratios, PBP had the least protein contamination, significantly better than the other methods (P<0.05). All the isolated EVs expressed exosome-enriched proteins CD63, TSG101 and HSP70. Incubation of the trophoblast JEG-3 cells with an equal amount of the fluorescence-labelled EVs isolated by the studied methods showed that many of the PBP-EVs treated cells were fluorescence positive but only a few cells were labelled in the UC- and UF-EVs treated groups. Moreover, the PBP-EVs could transfer significantly more miRNA to the recipient cells than the other 3 methods (P<0.05). The PBP method could isolate EVs from mouse ULF; the diameter of the isolated EVs was 62±19 nm and expressed CD63, TSG101 and HSP70 proteins. In conclusion, PBP could best preserve the activities of the isolated EVs among the 4 methods studied and was able to isolate EVs from a small volume of sample. The simple setup and low equipment demands makes PBP the most suitable method for rapid EV assessment and isolation of EVs in clinical and basic research settings.

Introduction Stem cells from the apical papilla (SCAP) are a type of mesenchymal stem cells found in the developing tissue, apical papilla, of immature permanent teeth. Studies have shown that SCAP are likely to be a source of primary odontoblasts that are responsible for the formation of root dentin. Basic fibroblast growth factor (bFGF) is a signaling molecule and pleiotropic growth factor involved in tooth root development, and it promotes proliferation of a variety of cell types. The effects of bFGF on SCAP, however, have not been examined. Methods We investigated the regulatory effects of bFGF on the proliferation and differentiation potential of human SCAP in vitro. Changes in the cell cycle and proliferation, colony-forming unit–fibroblastic formation, alkaline phosphatase (ALP) activity, osteogenic/dentinogenic differentiation, and stem cell gene makers of SCAP, cultured in the presence or absence of bFGF, were evaluated. Results Treatment with 5 ng/mL bFGF significantly increased SCAP proliferation and their colony-forming unit–fibroblastic formation efficiency. The growth factor also increased the expression of STRO-1 and the stem cell gene makers Nanog, Oct4, Sox2, and Rex1 in SCAP. In contrast, bFGF reduced the ALP activity, mineral nodule formation, and the expression of ALP, osteocalcin, bone sialoprotein, and dentin sialophosphoprotein. When SCAP cultures were expanded in the presence of bFGF for 1 week, subsequent stimulation of the osteogenic/dentinogenic condition resulted in enhanced differentiation. Conclusions Under certain conditions, bFGF enhances SCAP stemness by up-regulating stem cell gene expression, increasing proliferation ability, and potentiating differentiation potency.

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Previous studies have suggested that periodontal ligament stem cells (PDLSCs) play crucial role in regeneration of periodontal defects, and recently tissue engineering based on PDLSCs to enhance periodontal regeneration has been the focus of periodontal research. A theoretical way to achieve this goal would be to provide a "stimulatory'' environment to rapidly expand PDLSCs in vitro to expedite tissue engineering of periodontium. We hypothesize that three-dimensional (3D) dynamic simulated microgravity (SMG) culture system have effect on periodontal stem cells, and would benefit periodontal stem cells proliferation and differentiation, but up to now, there are no related reports on this aspect. In this study, we investigated the biological effect of three-dimensional dynamic SMG induced by rotary cell culture system (RCCS) on human periodontal ligament stem cells (hPDLSCs) in vitro. hPDLSCs were isolated from surgically extracted human teeth and enriched by collecting multiple colonies. hPDLSCs were inoculated on Cytodex 3 microcarriers and cultured in RCCS. The results showed that SMG affected the biology of hPDLSCs as indicated by promotion of proliferation and viability, alterations of morphology, and disorganization of microfilament system. Besides, SMG-treated hPDLSCs presented increased matrix mineralization and up-regulated expression of mineralization associated genes after incubation in osteogenic medium. For it is the first time to investigate effects of SMG on PDLSCs, the research may lend insight into variations of cell response in 3D environment, and contribute to achievement of desirable periodontal regeneration utilizing PDLSCs-based tissue engineering approaches.

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