Characterization of Extracellular Vesicles by Transmission Electron Microscopy and Immunolabeling Electron Microscopy

Subcellular particles for characterization of host-parasite interactions

Parasitic diseases remain a major global health problem for humans. Parasites employ a variety of strategies to invade and survive within their hosts and to manipulate host defense mechanisms, always in the pathogen's favor. Extracellular vesicles (EVs), membrane-bound nanospheres carrying a variety of bioactive compounds, were shown to be released by the parasites during all stages of the infection, enabling growth and expansion within the host and adaptation to frequently changing environmental stressors. In this review, we discuss how the use of existing nanotechnologies and high-resolution imaging tools assisted in revealing the role of EVs during parasitic infections, enabling the quantitation, visualization, and detailed characterization of EVs. We discuss here the cases of malaria, Chagas disease and leishmaniasis as examples of parasitic neglected tropical diseases (NTDs). Unraveling the EVs' role in the NTD pathogenesis may enormously contribute to their early and reliable diagnostic, effective treatment, and prevention.

Insight into the Functional Dynamics and Challenges of Exosomes in Pharmaceutical Innovation and Precision Medicine

Of all the numerous nanosized extracellular vesicles released by a cell, the endosomal-originated exosomes are increasingly recognized as potential therapeutics, owing to their inherent stability, low immunogenicity, and targeted delivery capabilities. This review critically evaluates the transformative potential of exosome-based modalities across pharmaceutical and precision medicine landscapes. Because of their precise targeted biomolecular cargo delivery, exosomes are posited as ideal candidates in drug delivery, enhancing regenerative medicine strategies, and advancing diagnostic technologies. Despite the significant market growth projections of exosome therapy, its utilization is encumbered by substantial scientific and regulatory challenges. These include the lack of universally accepted protocols for exosome isolation and the complexities associated with navigating the regulatory environment, particularly the guidelines set forth by the U.S. Food and Drug Administration (FDA). This review presents a comprehensive overview of current research trajectories aimed at addressing these impediments and discusses prospective advancements that could substantiate the clinical translation of exosomal therapies. By providing a comprehensive analysis of both the capabilities and hurdles inherent to exosome therapeutic applications, this article aims to inform and direct future research paradigms, thereby fostering the integration of exosomal systems into mainstream clinical practice.

A mitochondrial NADPH-cholesterol axis regulates extracellular vesicle biogenesis to support hematopoietic stem cell fate

Mitochondrial fatty acid oxidation (FAO) is essential for hematopoietic stem cell (HSC) self-renewal; however, the mechanism by which mitochondrial metabolism controls HSC fate remains unknown. Here, we show that within the hematopoietic lineage, HSCs have the largest mitochondrial NADPH pools, which are required for proper HSC cell fate and homeostasis. Bioinformatic analysis of the HSC transcriptome, biochemical assays, and genetic inactivation of FAO all indicate that FAO-generated NADPH fuels cholesterol synthesis in HSCs. Interference with FAO disturbs the segregation of mitochondrial NADPH toward corresponding daughter cells upon single HSC division. Importantly, we have found that the FAO-NADPH-cholesterol axis drives extracellular vesicle (EV) biogenesis and release in HSCs, while inhibition of EV signaling impairs HSC self-renewal. These data reveal the existence of a mitochondrial NADPH-cholesterol axis for EV biogenesis that is required for hematopoietic homeostasis and highlight the non-stochastic nature of HSC fate determination.

Link between organic nanovescicles from vegetable kingdom and human cell physiology: intracellular calcium signalling

BACKGROUND

Plant-derived nanovesicles (PDNVs) are a novelty in medical and agrifood environments, with several studies exploring their functions and potential applications. Among fruits, apples (sp. Malus domestica) have great potential as PDNVs source, given their widespread consumption, substantial waste production, and recognized health benefits. Notably, apple-derived nanovesicles (ADNVs) can interact with human cell lines, triggering anti-inflammatory and antioxidant responses. This work is dedicated to the comprehensive biochemical characterization of apple-derived nanovesicles (ADNVs) through proteomic and lipidomic analysis, and small RNAs sequencing. This research also aims to shed light on the underlying mechanism of action (MOA) when ADNVs interface with human cells, through observation of intracellular calcium signalling in human fibroblasts, and to tackles differences in ADNVs content when isolated from fruits derived from integrated and organic production methods cultivars.

RESULTS

The ADNVs fraction is mainly composed of exocyst-positive organelles (EXPOs) and MVB-derived exosomes, identified through size and molecular markers (Exo70 and TET-3-like proteins). ADNVs' protein cargo is heterogeneous and exhibits a diverse array of functions, especially in plant's protection (favouring ABA stress-induced signalling, pathogen resistance and Reactive Oxygen Species (ROS) metabolism). Noteworthy plant miRNAs also contribute to phytoprotection. In relation with human cells lines, ADNVs elicit spikes of intracellular Ca2+ levels, utilizing the cation as second messenger, and produce an antioxidant effect. Lastly, organic samples yield a substantial increase in ADNV production and are particularly enriched in bioactive lysophospholipids.

CONCLUSIONS

We have conclusively demonstrated that ADNVs confer an antioxidant effect upon human cells, through the initiation of a molecular pathway triggered by Ca2+ signalling. Within ADNVs, a plethora of bioactive proteins, small RNAs, and lipids have been identified, each possessing well-established functions within the realm of plant biology. While ADNVs predominantly function in plants, to safeguard against pathogenic agents and abiotic stressors, it is noteworthy that proteins with antioxidant power might act as antioxidants within human cells.

Physical association of low density lipoprotein particles and extracellular vesicles unveiled by single particle analysis

Extracellular vesicles (EVs) in blood plasma are recognized as potential biomarkers for disease. Although blood plasma is easily obtainable, analysis of EVs at the single particle level is still challenging due to the biological complexity of this body fluid. Besides EVs, plasma contains different types of lipoproteins particles (LPPs), that outnumber EVs by orders of magnitude and which partially overlap in biophysical properties such as size, density and molecular makeup. Consequently, during EV isolation LPPs are often co-isolated. Furthermore, physical EV-LPP complexes have been observed in purified EV preparations. Since co-isolation or association of LPPs can impact EV-based analysis and biomarker profiling, we investigated the presence and formation of EV-LPP complexes in biological samples by using label-free atomic force microscopy, cryo-electron tomography and synchronous Rayleigh and Raman scattering analysis of optically trapped particles and fluorescence-based high sensitivity single particle flow cytometry. Furthermore, we evaluated the impact on flow cytometric analysis in the presence of LPPs using in vitro spike-in experiments of purified tumour cell line-derived EVs in different classes of purified human LPPs. Based on orthogonal single-particle analysis techniques we demonstrate that EV-LPP complexes can form under physiological conditions. Furthermore, we show that in fluorescence-based flow cytometric EV analysis staining of LPPs, as well as EV-LPP associations, can influence quantitative and qualitative EV analysis. Lastly, we demonstrate that the colloidal matrix of the biofluid in which EVs reside impacts their buoyant density, size and/or refractive index (RI), which may have consequences for down-stream EV analysis and EV biomarker profiling.