Stem cells can be used for regenerative medicine and as treatments for disease. The application of tissue engineering-related transplantation, stem cells, and local changes in the microenvironment is expected to solve major medical problems. Currently, most studies focus on tissue repair and regeneration, and mesenchymal stem cells (MSCs) are among the most common research topics. MSCs are applicable as seed cells, and they represent one of the current hot topics in regenerative medicine research. However, due to storage limitations and because cell senescence occurs during in vitro expansion, their clinical application is challenging. Exosomes, which are secreted by MSCs through paracrine signalling, not only have the same effects as MSCs, but they also have the advantages of targeted delivery, low immunogenicity, and high repairability. This article reviews the acquisition methods, characteristics, biological functions, and clinical applications of exosomes.

Nanoscale replication of the hierarchical organization of minerals in biogenic mineralized tissues is believed to contribute to the better mechanical properties of biomimetic collagen scaffolds. Here, an intrafibrillar nanocarbonated apatite assembly is reported, which has a bone‐like hierarchy, and which improves the mechanical and biological properties of the collagen matrix derived from fibril‐apatite aggregates. A modified biomimetic approach is used, which based on the combination of poly(acrylic acid) as sequestration and sodium tripolyphosphate as templating matrix‐protein analogs. With this modified dual‐analog‐based biomimetic approach, the hierarchical association between collagen and the mineral phase is discerned at the molecular and nanoscale levels during the process of intrafibrillar collagen mineralization. It is demonstrated by nanomechanical testing, that intrafibrillarly mineralized collagen features a significantly increased Young's modulus of 13.7 ± 2.6 GPa, compared with pure collagen (2.2 ± 1.7 GPa) and extrafibrillarly‐mineralized collagen (7.1 ± 1.9 GPa). Furthermore, the hierarchy of the nanocarbonated apatite assembly within the collagen fibril is critical to the collagen matrix's ability to confer key biological properties, specifically cell proliferation, differentiation, focal adhesion, and cytoskeletal arrangement. The availability of the mineralized collagen matrix with improved nanomechanics and cytocompatibility may eventually result in novel biomaterials for bone grafting and tissue‐engineering applications.

Organ development requires complex signaling by cells in different tissues. Epithelium and mesenchyme interactions are crucial for the development of skin, hair follicles, kidney, lungs, prostate, major glands, and teeth. Despite myriad literature on cell–cell interactions and ligand–receptor binding, the roles of extracellular vesicles in epithelium–mesenchyme interactions during organogenesis are poorly understood. Here, we discovered that ~100 nm exosomes were secreted by the epithelium and mesenchyme of a developing tooth organ and diffused through the basement membrane. Exosomes were entocytosed by epithelium or mesenchyme cells with preference by reciprocal cells rather than self-uptake. Exosomes reciprocally evoked cell differentiation and matrix synthesis: epithelium exosomes induce mesenchyme cells to produce dentin sialoprotein and undergo mineralization, whereas mesenchyme exosomes induce epithelium cells to produce basement membrane components, ameloblastin and amelogenenin. Attenuated exosomal secretion by Rab27a/b knockdown or GW4869 disrupted the basement membrane and reduced enamel and dentin production in organ culture and reduced matrix synthesis and the size of the cervical loop, which harbors epithelium stem cells, in Rab27aash/ash mutant mice. We then profiled exosomal constituents including miRNAs and peptides and further crossed all epithelium exosomal miRNAs with literature-known miRNA Wnt regulators. Epithelium exosome-derived miR135a activated Wnt/β-catenin signaling and escalated mesenchymal production of dentin matrix proteins, partially reversible by Antago-miR135a attenuation. Our results suggest that exosomes may mediate epithelium–mesenchyme crosstalk in organ development, suggesting that these vesicles and/or the molecular contents they are transporting may be interventional targets for treatment of diseases or regeneration of tissues.

An aqueous Heck reaction carried out under ultrasonic irradiation at the ambient temperature (25 degrees C) has been shown in this study to afford high yields of corresponding products. It was found that as a catalyst for the reaction palladium forms nanoparticles in-situ, characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses, and can be recycled. Furthermore, the Heck reaction under such mild and environmentally friendly conditions offers excellent regioselectivity of para- over ortho-substitution in phenyl iodides especially with electron-donating groups.

To develop environmentally benign processes for C-C bond formation, electrochemistry is applied in a tin-mediated allylation reaction in water. In this electrochemical process, the corresponding homoallylic alcohols are prepared in excellent yields, while both tin salt and water can be recycled and electrode materials are not consumed.

No abstract

No abstract

Carboxylic acid esters Q 0530Catalysis and Regioselectivity of the Aqueous Heck Reaction by Pd (0) Nanoparticles under Ultrasonic Irradiation. -It is found that Pd nanoparticles generated in situ under ultrasonic irradiation efficiently catalyze the aqueous Heck reaction at ambient temperature [cf. conditions A) and B)] and allow para-selective monosubstitution. Polysubstitution takes place at high temperature under conditions C). -(ZHANG, Z.; ZHA, Z.; GAN, C.; PAN, C.; ZHOU, Y.; WANG*, Z.; ZHOU, M.-M.; J.