Mesenchymal stem cells (MSCs) have emerged as a potent therapeutic tool for the treatment of a number of pathologies, including immune pathologies. However, unwelcome effects of MSCs on blood coagulation have been reported, motivating us to explore the thrombotic properties of human MSCs from the umbilical cord. We revealed strong procoagulant effects of MSCs on human blood and platelet-free plasma using rotational thromboelastometry and thrombodynamic tests. A similar potentiation of clotting was demonstrated for MSC-derived extracellular vesicles (EVs). To offer approaches to avoid unwanted effects, we studied the impact of a heparin supplement on MSC procoagulative properties. However, MSCs still retained procoagulant activity toward blood from children receiving a therapeutic dose of unfractionated heparin. An analysis of the mechanisms responsible for the procoagulant effect of MSCs/EVs revealed the presence of tissue factor and other proteins involved in coagulation-associated pathways. Also, we found that some MSCs and EVs were positive for annexin V, which implies the presence of phosphatidylserine on their surfaces, which can potentiate clot formation. Thus, we revealed procoagulant activity of MSCs/EVs associated with the presence of phosphatidylserine and tissue factor, which requires further analysis to avoid adverse effects of MSC therapy in patients with a risk of thrombosis.

Plant viruses are biologically safe for mammals and can be successfully used as a carrier/platform to present foreign epitopes in the course of creating novel putative vaccines. However, there is mounting evidence that plant viruses, their virus-like and structurally modified particles may also have an immunopotentiating effect on antigens not bound with their surface covalently. Here, we present data on the adjuvant properties of plant viruses with various shapes (Tobacco mosaic virus, TMV; Potato virus X, PVX; Cauliflower mosaic virus, CaMV; Bean mild mosaic virus, BMMV) and structurally modified TMV spherical particles (SPs). We have analysed the effectiveness of immune response to individual model antigens (ovalbumin, OVA/hen egg lysozyme, HEL) and to OVA/HEL in compositions with plant viruses/SPs, and have shown that CaMV, TMV and SPs can effectively induce total IgG titers to model antigen. Some intriguing data were obtained when analysing the immune response to the plant viruses/SPs themselves. Strong immunity was induced to CaMV, BMMV and PVX, whereas TMV and SPs stimulated considerably lower self-IgG titers. Our results provide new insights into the immunopotentiating properties of plant viruses and can be useful in devising adjuvants based on plant viruses.

A recombinant vaccine candidate has been developed based on the major coronaviruses’ antigen (S protein) fragments and a novel adjuvant—spherical particles (SPs) formed during tobacco mosaic virus thermal remodeling. The receptor-binding domain and the highly conserved antigenic fragments of the S2 protein subunit were chosen for the design of recombinant coronavirus antigens. The set of three antigens (Co1, CoF, and PE) was developed and used to create a vaccine candidate composed of antigens and SPs (SPs + 3AG). Recognition of SPs + 3AG compositions by commercially available antibodies against spike proteins of SARS-CoV and SARS-CoV-2 was confirmed. The immunogenicity testing of these compositions in a mouse model showed that SPs improved immune response to the CoF and PE antigens. Total IgG titers against both proteins were 9–16 times higher than those to SPs. Neutralizing activity against SARS-CoV-2 in serum samples collected from hamsters immunized with the SPs + 3AG was demonstrated.

Mesenchymal stromal cells (MSC) are widely recognized as potential effectors in neuroprotective therapy. The protective properties of MSC were considered to be associated with the secretion of extracellular vesicles (MSC-EV). We explored the effects of MSC-EV in vivo on models of traumatic and hypoxia-ischemia (HI) brain injury. Neuroprotective mechanisms triggered by MSC-EV were also studied in vitro using a primary neuroglial culture. Intranasal administration of MSC-EV reduced the volume of traumatic brain damage, correlating with a recovery of sensorimotor functions. Neonatal HI-induced brain damage was mitigated by the MSC-EV administration. This therapy also promoted the recovery of sensorimotor functions, implying enhanced neuroplasticity, and MSC-EV-induced growth of neurites in vitro supports this. In the in vitro ischemic model, MSC-EV prevented cell calcium (Ca 2+ ) overload and subsequent cell death. In mixed neuroglial culture, MSC-EV induced inositol trisphosphate (IP3) receptor-related Ca 2+ oscillations in astrocytes were associated with resistance to calcium overload not only in astrocytes but also in co-cultured neurons, demonstrating intercellular positive crosstalk between neural cells. This implies that phosphatidylinositol 3-Kinase/AKT signaling is one of the main pathways in MSC-EV-mediated protection of neural cells exposed to ischemic challenge. Components of this pathway were identified among the most enriched categories in the MSC-EV proteome.

Extracellular vesicles (EV) derived from stem cells have become an effective complement to the use in cell therapy of stem cells themselves, which has led to an explosion of research into the mechanisms of vesicle formation and their action. There is evidence demonstrating the presence of mitochondrial components in EV, but a definitive conclusion about whether EV contains fully functional mitochondria has not yet been made. In this study, two EV fractions derived from mesenchymal stromal stem cells (MSC) and separated by their size were examined. Flow cytometry revealed the presence of mitochondrial lipid components capable of interacting with mitochondrial dyes MitoTracker Green and 10-nonylacridine orange; however, the EV response to the probe for mitochondrial membrane potential was negative. Detailed analysis revealed components from all mitochondria compartments, including house-keeping mitochondria proteins and DNA as well as energy-related proteins such as membrane-localized proteins of complexes I, IV, and V, and soluble proteins from the Krebs cycle. When assessing the functional activity of mitochondria, high variability in oxygen consumption was noted, which was only partially attributed to mitochondrial respiratory activity. Our findings demonstrate that the EV contain all parts of mitochondria; however, their independent functionality inside EV has not been confirmed, which may be due either to the absence of necessary cofactors and/or the EV formation process and, probably the methodology of obtaining EV.