Vol 65, No 3 (2023)

Pluripotent stem cells (PSCs), represented primarily by embryonic stem cells and induced pluripotent stem cells (iPSCs), have a unique ability to self-renew and differentiate into all types of somatic cells. Dissecting molecular mechanisms controlling these properties is important for an efficient and safe introduction of PSCs into clinics. Growing evidence indicates that the proteostasis plays a central role in PSCs fate decisions. This review focuses on the role of the ubiquitin-proteasome system, a key member of the proteostasis network, in the regulation of pluripotency and differentiation of PSCs.

SIM-A9 is a line of spontaneously immortalized mouse microglia cells obtained from newborn C57BL/6 mice’s cerebrum. The aim of this work is to characterize SIM-A9 line by the ratio of cells with the resting and activated microglia phenotype, to analyze the expression of stem/progenitor cell markers CD133 and nestin, growth factors receptors CSF-1R and EGFR, and the karyotype of this line. The light microscopy, immunocytochemistry, flow cytometry and RT/PCR were used to analyze the morphology, phenotype, and gene expression levels of pro-inflammatory cytokines, and the mFISH method was used to analyze the karyotype. It was shown for the first time that SIM-A9 cells express a high level of TSPO protein, CD68, CD11b and CD45 markers on the surface membrane of cells, which corresponds to the phenotype of activated microglia. Despite this, the cells of this line respond with additional activation to LPS stimulation, which leads to an increase in the pro-inflammatory cytokine genes IL-1β, TNFα, IL-6 expression and a high level of active oxygen and nitrogen metabolites formation. It was shown that SIM-A9 cells express stem and progenitor cells markers, CD133⁺ and nestin, which allows us to consider the cells of this line as early poorly differentiated progenitor cells, despite their phenotype corresponding to activated microglia. It was also found that SIM-A9 cells express receptors of two growth factors CSF-1 and EGF, CSF-1R and EGFR, which indicates the possibility of SIM-A9 cells proliferation stimulation by two alternative mechanisms under the action of the corresponding factors. SIM-A9 cells have a hypotetraploid karyotype with a large number of structural and quantitative chromosome anomalies.

TiO₂ is widely used in industry and cosmetics and medicines production. In recent years, to achieve tumor-specific delivery of anticancer agents, TiO₂ nanoparticles have been used in chemo/photodynamic therapy, which may cause local increase of the TiO₂ concentration in tumors. The TiO₂ nanoparticles can affect various processes in tumors. One of such process is entosis. During entosis one tumor cell invades another tumor cell. The aim of this work was to study the effect of TiO2 nanoparticles (anatase <25 nm and rutil/anatase <75 nm; 1, 10 and 100 µg/mL, 72 hours) on the entosis in the human breast adenocarcinoma cell line (MCF7). Cultivation of cells in the presence of nanoparticles lead to a slowdown in proliferation and reduced in the entosis number. These effects were dose-dependent. Elemental analysis (analytical electron microscopy) showed presence TiO₂ nanoparticles in the cell vacuoles, in the cytosol and in the extracellular space. TiO₂ nanoparticles (10 µg/mL) significantly disrupted adhesive junctions in entotic cells and in cell culture in general (immunocytochemistry staining). The anatase nanoparticles induced p53 translocation into the nucleus. Thus, the obtained data showed that the TiO₂ nanoparticles inhibited entosis in MCF-7 cells by means of disrupting the adhesive junction formation and preventing cell invasion. However, failure of adhesive contacts can facilitate tumor metastasis.

Expansion microscopy (ExM) is a sample preparation method that allows to achieve improved visualization of structures due to the physical expansion of the sample. This method is used in combination with traditional light microscopy and allows, without the use of complex technical devices typical for super-resolution microscopy, to achieve visualization of biological structures with higher resolution. Unlike the methods of super-resolution microscopy, expansion microscopy does not make it possible to overcome the diffraction limit; however, the observed effect can be considered equivalent to an increase in the spatial resolution. The relative simplicity of the method and the undemanding nature of the microscope used have made expansion microscopy a fairly popular method to visualize various biological structures last time. This paper describes the use of expansion microscopy to visualize DNA and structures formed by the FtsZ protein in Escherichia coli cells during the SOS response. The results of the work confirm the previously obtained data that the FtsZ protein in cells in the state of the SOS response is unevenly distributed. The protocol used in this work for visualization of E. coli cells preliminarily fixed on the glass surface using the expansion microscopy method can be used in the future to study the internal structures of other cells, both bacterial and eukaryotic.