Exosomes are natural nanocontainers actively secreted by the body’s cells and transmitting molecular signals of various types to recipient cells. Cellular mechanisms of exosomes’ biogenesis involve specific sorting of RNA for incorporation into them. As a result, the molecular composition of exosomes is closely related to the donor cell’s functional state, and this makes exosomes an important diagnostic and prognostic marker in a number of diseases (primarily oncological). The ability of exosomes to transport biologically active molecules and to protect the cargo from degradation makes them nearly ideal candidates as delivery carriers of RNA in therapeutic or prophylactic regimes. Potential of exosomal surface functionalization enables improved targeting to specific organs, tissues and cells. However, the development of an effective technology for RNA’s loading into exosomes cannot be considered resolved. This review is focused on experimental data on the use of exosomes as vehicles for the delivery of therapeutic and prophylactic RNAs. We briefly consider the biogenesis and functions of exosomes, focusing on those biological properties that make them formidable candidates in the race to develop effective delivery carriers. Furthermore, we describe various techniques of cargo loading into exosomes. Prospects of exosomes application as therapeutic delivery system for siRNAs, miRNAs, and long RNAs are considered.

The sinoatrial node (SAN) is composed mostly of pacemaker, transitional and Purkinje‐like cells. Pacemaker cells, especially in the centre of the SAN, are surrounded by dense fibrous tissue and do not have any contact with transitional cells. We hypothesize that the SAN contains telocytes that have contacts with pacemaker cells and contractile myocardium. Immunohistochemistry using antibodies against HCN4 and antibody combinations against CD34 and HCN4 was carried out on 12 specimens. Confocal laser scanning microscopy (CLSM) with two mixtures of primary antibodies, namely CD34/S100 and vimentin/S100, was performed in three cases. In two cases, CLSM was carried out with CD117 antibody. Specimens for electron microscopy and immunocytochemistry with HCN4 immunogold labelling were taken from another three patients. In our study, we found cells with the immunophenotype of telocytes in the SAN. There were twice as many of these cells in the centre of the SAN as in the periphery (20.3 ± 4.8 versus 10.8 ± 4.4 per high‐power field). They had close contact with pacemaker cells and contractile cardiomyocytes and expressed HCN4. The ultrastructural characteristics of these cells are identical to those of telocytes observed earlier in other organs. Our study provides evidence that telocytes are present in the SAN.

In this study, we aimed to develop a technique for colloidal silver nanoparticle (AgNP) modification in order to increase their stability in aqueous suspensions. For this purpose, 40-nm spherical AgNPs were modified by the addition of either human albumin or Tween-80 (Polysorbate-80). After detailed characterization of their physicochemical properties, the hemolytic activity of the nonmodified and modified AgNPs was investigated, as well as their cytotoxicity and antimicrobial effects. Both albumin- and Tween-80-coated AgNPs demonstrated excellent stability in 0.9% sodium chloride solution (>12 months) compared to nonmodified AgNPs, characterized by their rapid precipitation. Hemolytic activity of nonmodified and albumin-coated AgNPs was found to be minimal, while Tween-80-modified AgNPs produced significant hemolysis after 1, 2, and 24 h of incubation. In addition, both native and Tween-80-covered AgNPs showed dose-dependent cytotoxic effects on human adipose-tissue-derived mesenchymal stem cells. The albumin-coated AgNPs showed minimal cytotoxicity. The antimicrobial effects of native and albumin-coated AgNPs against S. aureus, K. pneumonia, P. aeruginosa, Corynebacterium spp., and Acinetobacter spp. were statistically significant. We conclude that albumin coating of AgNPs significantly contributes to improve stability, reduce cytotoxicity, and confers potent antimicrobial action.

Secretion of extracellular vesicles (EVs) is a fundamental property of living cells. EVs are known to transfer biological signals between cells and thus regulate the functional state of recipient cells. Such vesicles mediate the intercellular transport of many biologically active molecules (proteins, nucleic acids, specific lipids) and participate in regulation of key physiological processes. In addition, EVs are involved in the pathogenesis of multiple diseases: infectious, neurodegenerative, and oncological. The current EV classification into microvesicles, apoptotic bodies, and exosomes is based on their size, pathways of cellular biogenesis, and molecular composition. This review is focused on analysis of the role of EVs (mainly exosomes) in the pathogenesis of viral infection. We briefly characterize the biogenesis and molecular composition of various EV types. Then, we consider EV-mediated pro- and anti-viral mechanisms. EV secretion by infected cells can be an important factor of virus spread in target cell populations, or a protective factor limiting viral invasion. The data discussed in this review, on the effect of EV secretion by infected cells on processes in neighboring cells and on immune cells, are of high significance in the search for new therapeutic approaches and for design of new generations of vaccines.

The design of cationic liposomes for efficient mRNA delivery can significantly improve mRNA-based therapies. Lipoplexes based on polycationic lipid 1,26-bis(cholest-5-en-3β-yloxycarbonylamino)-7,11,16,20-tetraazahexacosane tetrahydrochloride (2X3) and helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) were formulated in different molar ratios (1:1, 1:2, 1:3) to efficiently deliver model mRNAs to BHK-21 and A549. The objective of this study was to examine the effect of 2X3-DOPE composition as well as lipid-to-mRNA ratio (amino-to-phosphate group ratio, N/P) on mRNA transfection. We found that lipoplex-mediated transfection efficiency depends on both liposome composition and the N/P ratio. Lipoplexes with an N/P ratio of 10/1 showed nanometric hydrodynamic size, positive ζ potential, maximum loading, and transfection efficiency. Liposomes 2X3-DOPE (1:3) provided the superior delivery of both mRNA coding firefly luciferase and mRNA-eGFP into BHK-21 cells and A549 cells, compared with commercial Lipofectamine MessengerMax.

Samples of coelomic epithelium (CE) and coelomocyte suspension of intact and wounded starfish Asterias rubens L. were studied by electron microscopy. The CE was shown to be composed of three types of cells: flagellar (approximately 60%), secretory (approximately 3%), and myoepithelial (approximately 37%); flagellar and secretory cells form the CE apical surface. Secretory cells are represented by two subtypes, i.e., granular and mucous secretory cells. Myoepithelial cells are located in the basal zone of the epithelium. In 4–5% of cases, adjacent flagellar cells are separated by various sizes of intercellular gaps. These gaps seem to be lacunae left by the flagellar cells after their release into the coelomic cavity. The morphological pattern of the conversion of CE flagellar cells into coelomocytes was characterized. After a moderate wounding used in the present study, no significant structural alterations in the CE organization were revealed. In coelomocyte suspension, small rounded young coelomocytes (approximately 3%) and the larger mature coelomocytes (approximately 97%) were found. On the surface of one of the young coelomocytes, a flagellum was revealed. Surface of the mature coelomocytes forms processes of various size and structure; their cytoplasm contains lysosomes and phagocytic vacuoles of different size. After wounding, a coelomocyte activation was found that consisted of a sharp rise in the number and length of filopodia on their surface, as well as the formation of multicellular aggregates. The complex of ultrastructural data allows it to be suggested that the histogenesis of coelomocytes from CE flagellar cells is a process of cell transdifferentiation.