Apoptosis is a widely controlled, programmed cell death, defects in which are the source of various diseases such as neurodegenerative diseases as well as cancer. The use of apoptosis in the therapy of various human diseases is of increasing interest, and the analysis of the factors involved in its regulation is valuable in designing specific carriers capable of targeting cell death. Highly efficient and precisely controlled delivery of genetic material by low-toxic carriers is one of the most important challenges of apoptosis-based gene therapy. In this work, we investigate the effect of the star polymer with 28 poly(N,N′-dimethylaminoethyl methacrylate) arms (STAR) on human cells, according to its concentration and structure. We show that star polymer cytotoxicity increases within its concentration and time of cells treatment. Except for cytotoxic effect, we observe morphological changes such as a shrinkage, loss of shape and begin to detach. We also prove DNA condensation after star polymer treatment, one of the most characteristic feature of apoptosis. The results indicate that the use of STAR triggers apoptosis in cancer cells compared to various normal cells, what makes these nanoparticles a promising drug in therapeutic strategy, which targets apoptosis. We demonstrate highlighting potential of star polymers as an innovative tool for anti-cancer therapy.

We studied the spatial conformation and activity of mitochondria in the developing syncytial male germline cysts during spermatogenesis of the medicinal leeches using light, fluorescent, transmission electron microscopy, and serial block-face scanning electron microscopy. In cysts with spermatogonia and spermatocytes, mitochondria form networks and are in a dynamic hyperfusion state, while in cysts with spermatids, a single huge mitochondrion is observed. As spermiogenesis progresses, this huge mitochondrion is finally located in the future midpiece. The highest activity, in terms of membrane potential, of the mitochondria in H. medicinalis germline cysts was observed in cysts with spermatocytes; the lowest was in cysts with late elongated spermatids.

Epithelial–mesenchymal plasticity encompasses a spectrum of epithelial and mesenchymal identity states that enable cells to adapt to changing biological contexts. While CD44 isoform usage and epithelial splicing regulators ESRP1/2 are well-characterized in cancer-associated epithelial–mesenchymal transition (EMT), their regulation across physiological, non-transformed identity states remains less well defined. Here, we employed a non-malignant human cellular system comprising primary dermal fibroblasts, induced pluripotent stem (iPS) cells, and iPS-derived mesenchymal stem cells (iPS-MSCs) to define discrete epithelial, intermediate epithelial/mesenchymal, and mesenchymal identity states positioned along an epithelial–mesenchymal identity axis. Morphological assessment, lineage marker profiling, and RT-qPCR analyses revealed reproducible population-level stratification of these states. CD44 expression and alternative splicing followed this hierarchy, with CD44s predominating in fibroblasts, broad variant exon inclusion in iPS cells, and intermediate patterns in iPS-MSCs. ESRP1 expression mirrored CD44 splicing architecture, and ESRP1 silencing in iPS cells induced a shift toward CD44s, confirming its functional contribution to epithelial-associated CD44 splicing. In contrast, Notch-related transcriptional readouts displayed distinct, context-dependent profiles across the examined identity states. Together, this study establishes a tractable non-transformed human model that captures selected molecular features associated with epithelial–mesenchymal plasticity beyond malignant contexts.

Serial block-face scanning electron microscopy (SBEM) is a powerful technique for three-dimensional ultrastructural analysis of biological samples, though its application to in vitro cultured human cells remains underutilized. In this study, we present an optimized SBEM sample preparation protocol using human dermal fibroblasts and induced pluripotent stem cells (iPSCs). The method includes key modifications to the original protocol, such as using only glutaraldehyde for fixation and substituting the toxic cacodylate buffer with a less hazardous phosphate buffer. These adaptations result in excellent preservation of cellular ultrastructure, with high contrast and clarity, as validated by transmission electron microscopy (TEM). The loss of natural cell morphology resulted from fixation during passage, when cells formed a precipitate, rather than from fixation directly within the culture medium. The protocol is time-efficient, safe, and broadly applicable to both stem cells and differentiated cells cultured under 2D conditions, providing a valuable tool for ultrastructural analysis in diverse biomedical research settings.