Ligand–receptor complexes formed at the plasma membrane are internalised via various endocytic pathways that influence the ultimate signalling output by regulating the selection of interaction partners by the complex along the trafficking route. We report that, in differentiated cells, activin A–receptor complexes are internalised via clathrin-mediated endocytosis (CME) and macropinocytosis (MP), whereas in human embryonic stem cells (hESCs) internalisation occurs via CME. We further show that hESCs are devoid of MP, which becomes functional upon differentiation towards endothelial cells through mesoderm mediators. Our results reveal, for the first time, that MP is an internalisation route for activin A in differentiated cells, and that MP is not active in hESCs and is induced as cells differentiate.

Background/Objectives: The inner blood–retinal barrier (iBRB) is a specialized neurovascular interface essential for retinal homeostasis and visual function and is compromised in several vision-threating conditions. Therefore, the ability to model iBRB function and dysfunction in a controlled, reproducible and scalable manner is crucial for pharmaceutical research. However, the complex anatomy and physiology of the iBRB raise challenges for cell-based in vitro modeling. Methods/Results: This review follows the evolution of iBRB models—from simple monolayers of retinal endothelial cells (ECs) to sophisticated multicellular microphysiological systems (MPs). Advanced diverse microfluidic platforms aim to replicate key structural, biochemical and functional aspects of the iBRB, each incorporating distinct strategies regarding cell sourcing, device design, flow dynamics and functional readouts. Conclusions: Despite their limitations, these models are highly valuable for drug screening and mechanistic studies aimed at preserving or restoring barrier integrity while also helping to bridge the translational gap in ophthalmic drug discovery.

The role of oxidative stress in chronic pathological conditions of the nervous system is well-established, contributing to neuronal dysfunction and cell death. Numerous studies have sought pharmacologic agents with antioxidant effects for neurons, with controversial results. Our study aims to establish a valid and reproducible in vitro oxidative stress model in neurons, simulating initial stages of neurodegenerative disorders, focusing on morphological alterations in the dendritic field of neurons. Primary hippocampal cells from newborn rat brains were cultured for two weeks, and subsequently, different concentrations of hydrogen peroxide (H₂O₂) were applied for 24 h in cultures. Cell viability assays and flow cytometry were carried out to measure H₂O₂ effects on apoptosis, necrosis, and reactive oxygen species production. Finally, morphometric evaluation of the neuronal dendritic field was conducted, focused on dendritic length, branching, and spine density, with ImageJ software following immunostaining of neurons. Administration of 100 μΜ H₂O₂ for 24 h in primary hippocampal cultures resulted in significant alterations in dendritic morphology (one-way ANOVA, p < 0.05), without significantly affecting cell viability. These results demonstrate the impact of H₂O₂ on neuronal morphology and suggest that dendritic and spinal alterations could serve as sensitive markers of mild oxidative stress on neurons, prior to the activation of apoptotic mechanisms. This can be used as a surrogate model for the initial stages of neurodegenerative disorders when synaptic loss takes place, facilitating study of agent effectiveness with antioxidant therapeutic potential.

Mulberry fruits are rich sources of bioactive phytochemicals with potential cardiovascular-relative bioactivity properties. In the present study, phenolic/alkaloid-enriched extracts from black (Morus nigra) and white (Morus alba) mulberries were chemically characterized and evaluated for their anti-atherogenic and antiplatelet activities in vitro. LC-HRMS analysis revealed distinct phytochemical profiles, with the black mulberry extract (BlackM) being characterized by a high abundance of anthocyanins, predominantly cyanidin- and pelargonidin-based glycosides, whereas the white mulberry extract (WhiteM) was particularly rich in pyrrolidine alkaloids, including morusimic acid isomers. Both extracts also contain flavonoids and phenolic acids, such as rutin, quercetin derivatives, and chlorogenic acid derivatives. BlackM markedly increased the resistance of low-density lipoprotein (LDL) to Cu²⁺-induced oxidation, whereas WhiteM more effectively inhibited the propagation phase of lipid peroxidation and significantly suppressed arachidonic acid-induced platelet aggregation. BlackM induced a modest, albeit non-significant, reduction in neutrophil extracellular trap (NET) formation. To the best of our knowledge, this is among the first studies to comparatively investigate the effects of black and white mulberry extracts on LDL oxidation, platelet aggregation and NETs formation. Overall, these findings support the potential use of mulberry-derived phytochemicals as functional food ingredients and nutraceuticals for the prevention of atherothrombotic cardiovascular disease.