Characteristics of Extracellular Vesicles and Preclinical Testing Considerations Prior to Clinical Applications

Advances in Tracing Techniques: Mapping the Trajectory of Mesenchymal Stem-Cell-Derived Extracellular Vesicles

Mesenchymal stem-cell-derived extracellular vesicles (MSC-EVs) are nanoscale lipid bilayer vesicles secreted by mesenchymal stem cells. They inherit the parent cell's attributes, facilitating tissue repair and regeneration, promoting angiogenesis, and modulating the immune response, while offering advantages like reduced immunogenicity, straightforward administration, and enhanced stability for long-term storage. These characteristics elevate MSC-EVs as highly promising in cell-free therapy with notable clinical potential. It is critical to delve into their pharmacokinetics and thoroughly elucidate their intracellular and in vivo trajectories. A detailed summary and evaluation of existing tracing strategies are needed to establish standardized protocols. Here, we have summarized and anticipated the research progress of MSC-EVs in various biomedical imaging techniques, including fluorescence imaging, bioluminescence imaging, nuclear imaging (PET, SPECT), tomographic imaging (CT, MRI), and photoacoustic imaging. The challenges and prospects of MSC-EV tracing strategies, with particular emphasis on clinical translation, have been analyzed, with promising solutions proposed.

Surface Components and Biological Interactions of Extracellular Vesicles

Extracellular vesicles (EVs) are critical mediators of intercellular communication, carrying bioactive cargo and displaying diverse surface components that reflect their cellular origins and functions. The EV surface, composed of proteins, lipids, and glycocalyx elements, plays a pivotal role in targeting recipient cells, mediating biological interactions, and enabling selective cargo delivery. This review comprehensively examined the molecular architecture of EV surfaces, linking their biogenesis to functional diversity, and highlights their therapeutic and diagnostic potential in diseases such as cancer and cardiovascular disorders. Additionally, we explore emerging applications of EVs, including machine-learning-assisted analysis, chemical integration, and cross-system combinations. The review also discusses some key challenges in the clinical translation of EV-related technologies.

miR-21-5p Enriched Exosomes from Human Embryonic Stem Cells Promote Osteogenesis via YAP1 Modulation

Purpose

To investigate the osteogenic potential of human embryonic stem cell-derived exosomes (hESC-Exos) and their effects on the differentiation of human umbilical cord mesenchymal stem cells (hUCMSCs).

Methods

hESC-Exos were isolated and characterized using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting. hUCMSCs were cultured with hESC-Exos to assess osteogenic differentiation through alizarin red staining, quantitative PCR (qPCR), and Western blotting. miRNA profiling of hESC-Exos was performed using miRNA microarray analysis. In vivo bone regeneration was evaluated using an ovariectomized rat model with bone defects treated with exosome-loaded scaffolds.

Results

hESC-Exos significantly promoted the osteogenic differentiation of hUCMSCs, as evidenced by increased alizarin red staining and the upregulation of osteogenesis-related genes and proteins (ALP, RUNX2, OCN). miRNA analysis revealed that miR-21-5p is a key regulator that targets YAP1 and activates the Wnt/β-catenin signaling pathway. In vivo, hESC-Exos enhanced bone repair in ovariectomized rats, as demonstrated by increased bone mineral density and improved bone microarchitecture compared to those in controls.

Conclusion

hESC-Exos exhibit significant osteogenic potential by promoting the differentiation of hUCMSCs and enhancing bone regeneration in vivo. This study revealed that the miR-21-5p-YAP1/β-catenin axis is a critical pathway, suggesting that the use of hESC-Exos is a promising therapeutic strategy for bone regeneration and repair.

Dual roles of extracellular vesicles in acute lymphoblastic leukemia: implications for disease progression and theranostic strategies

Acute Lymphoblastic Leukemia (ALL) is a heterogeneous blood cancer characterized by the uncontrolled growth of immature lymphoid cells due to dysregulated signaling pathways. It is the most common pediatric cancer, with high cure rates in children, but significantly lower survival rates in adults. Current theranostic strategies, including chemotherapy, immunotherapy, and nanomedicine, aim to improve detection and treatment precision but are limited by side effects, drug resistance, high costs, and stability issues. Notably, extracellular vesicles (EVs) offer a promising alternative, addressing these limitations through their natural biocompatibility and targeted delivery capabilities. EVs play a dual role in ALL: they contribute to leukemia progression by promoting tumor growth, immune suppression, and drug resistance via the transfer of oncogenic molecules, while also serving as valuable non-invasive biomarkers due to their specific miRNA and protein content. Their ability to deliver therapeutic agents directly to leukemic cells, combined with their stability and low immunogenicity, makes EVs a compelling tool for improving ALL treatments. Indeed, by targeting the molecular pathways influenced by EVs or leveraging them for drug delivery, innovative therapeutic strategies can be developed to enhance treatment outcomes and reduce side effects. Thus, EVs represent a promising frontier for advancing theranostic strategies in ALL, offering new opportunities to improve diagnosis and treatment while overcoming the limitations of traditional therapies. This review will explore the dual roles of EVs in ALL, addressing their contributions to disease progression and their potential as therapeutic agents and biomarkers for early diagnosis and targeted therapies.

Extracellular Vesicles from Human Induced Pluripotent Stem Cells Exhibit a Unique MicroRNA and CircRNA Signature

Extracellular vesicles (EV) have emerged as promising cell-free therapeutics in regenerative medicine. However, translating primary cell line-derived EV to clinical applications requires large-scale manufacturing and several challenges, such as replicative senescence, donor heterogeneity, and genetic instability. To address these limitations, we used a reprogramming approach to generate human induced pluripotent stem cells (hiPSC) from the young source of cord blood mesenchymal stem/stromal cells (CBMSC). Capitalizing on their inexhaustible supply potential, hiPSC offer an attractive EV reservoir. Our approach encompassed an exhaustive characterization of hiPSC-EV, aligning with the rigorous MISEV2023 guidelines. Analyses demonstrated physical features compatible with small EV (sEV) and established their identity and purity. Moreover, the sEV-shuttled non-coding (nc) RNA landscape, focusing on the microRNA and circular RNA cargo, completed the molecular signature. The kinetics of the hiPSC-sEV release and cell internalization assays unveiled robust EV production and consistent uptake by human neurons. Furthermore, hiPSC-sEV demonstrated ex vivo cell tissue-protective properties. Finally, via bioinformatics, the potential involvement of the ncRNA cargo in the hiPSC-sEV biological effects was explored. This study significantly advances the understanding of pluripotent stem cell-derived EV. We propose cord blood MSC-derived hiPSC as a promising source for potentially therapeutic sEV.

3'-UTR Sequence of Exosomal NANOGP8 DNA as an Extracellular Vesicle-Localization Signal

Extracellular vesicles (EVs) are garnering attention as a safe and efficient biomolecule delivery system. EVs intrinsically play a crucial role in intercellular communication and pathophysiology by transporting functionally active DNA molecules. The internalized DNA pleiotropically affects the recipient cells. Considering these salient features, an intentional incorporation of specific DNA gene cassettes into EVs and their subsequent delivery to the target cells has potential applications in genetic engineering. Moreover, efficient ways to insert the DNA into EVs during their biogenesis is valuable. Our current research is a step in the development of this technology. As such, cancer cells are known to secrete exosomes containing increased amounts of double-stranded DNA than normal cells. The clonal analysis in our previously published data revealed that exosomes released from various cancer cells contained a significantly larger population of NANOGP8 DNA with a 22-base pair insertion in the 3'-untranslated region (UTR) compared to those secreted by normal cells. This finding led us to hypothesize that the 22-base pair insertion may act as a signal to facilitate the incorporation of NANOGP8 DNA into the exosomes. To test this hypothesis, we compared the EV localization of an Enhanced Green Fluorescent Protein (EGFP) gene fused with the NANOGP8 3'-UTR, with and without the 22-base pair insertion. The quantitative PCR analysis showed a significantly higher EGFP DNA accumulation in exosomes released from cells transfected with the gene cassette containing the 3'-UTR with the 22-base pair insertion. The discovery of a DNA localization signal in exosomal DNA's 3'-UTR could pave the way for the development of an EV-based DNA delivery system. This technology will open new possibilities in genetic engineering and innovative therapies using nucleic acid medicine.

A systematic review and meta-analysis of clinical trials assessing safety and efficacy of human extracellular vesicle-based therapy

Nowadays, it has become clear that extracellular vesicles (EVs) are not a cellular waste disposal vesicle but are an essential part of an intercellular communication system. Besides the use of EVs in biomarker studies and diagnostics, the potential of EV-therapeutics has been seen by many. They provide unique properties for disease therapy, including strong immune-modulatory actions, the possibility of engineering, low immunogenicity, and the capability of crossing biological barriers. Proof-of-concept of EV-therapeutics for various pathologies has been achieved in preclinical studies. However, clinical trials with EVs have only been emerging slowly. Here, we aim to provide a comprehensive overview of the current state-of-the-art concerning clinical studies using EVs in human therapy. By approaching the current knowledge in a systematic manner, we were able to include 21 reports for meta-analysis of safety and evaluation of efficacy outcomes. Overall, we have shown that EV-based therapy is safe with a low incidence of serious adverse events (SAE; 0.7% (95%-CI: 0.1-5.2%), and adverse events (AE; 4.4% (95%-CI: 0.7-22.2%). Subgroup analysis showed no significant difference in SAE when comparing autologous versus allogeneic administration, as well as engineered versus non-engineered EV products. A significantly higher number of AE was seen in autologous versus allogeneic administration. However, the clinical relevance remains questionable. Evaluation of the clinical outcomes of immunostimulatory, immunosuppressive or regenerative EV-therapies indicated improvement in the majority of treated patients. Despite these promising results, data need to be approached with caution due to a high heterogeneity in the EVs manufacturing methods, study design, and reporting of (S)AE. Overall, we conclude that EV-based therapy is safe and presents a promising opportunity in therapy. More efforts are needed in the standardization and harmonization of reporting of EV isolation and characterization data as well as in the reporting of (S)AE to allow inter-study comparison.

Mesenchymal Stem Cell-Derived Extracellular Vesicle Therapy for Asthma in Murine Models: A Systematic Review and Meta-analysis

BACKGROUND

Asthma is a common disease, and among the most predominant causes of the years lived with disability. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as a promising avenue for asthma management. The objective of this study is to perform a systematic review and meta-analysis of pre-clinical studies investigating the therapeutic use of MSC-EVs in murine models of asthma.

METHODS

A systematic search of electronic databases was performed. Meta-analyses were conducted on broncho-alveolar lavage fluid (BALF) cells and cytokines, as well as airway hyper-responsiveness Penh values and histological staining scores to determine the efficacy of MSC-EVs-based therapy, comparing treated rodents with untreated ones. BALF IL-4, BALF total cells, and BALF eosinophils were chosen as the primary outcomes, while airway hyper-responsiveness Penh values, BALF cytokines excluding IL-4, and histological staining scores were chosen as secondary outcomes.

RESULTS

A total of 19 eligible studies were included in the current systematic review, with 9 assessing BALF IL-4, 11 assessing BALF total cells, and 10 assessing BALF eosinophils. Pooled Hedges' g (p-value) for each outcome was - 4.407 (< 0.001), -4.976 (< 0.001), and - 4.071 (< 0.001), showing that MSC-EVs therapy inhibits asthma pathology. Changes in secondary outcomes also indicated a reduction in inflammation, goblet cell hyperplasia, and airway hyper-responsiveness. Subgroup analyses did not reveal significant disparities between the type of rodents and administration routes, and meta-regressions were only significant for MSC-EVs source and dose in the IL-4 meta-analysis, and for administration frequency and time from the last challenge to sacrifice in the BALF total cell meta-analysis.

CONCLUSION

This review highlights the current pre-clinical evidence of MSC-EVs therapy for asthma and finds its application ameliorates multiple aspects of asthma's pathology. We further underline the importance of MSC-EVs source, dose, administration frequency, and timing on the therapeutic effect and warrant further investigation and clinical translation to assess the best treatment regimen and to gauge the efficacy of EV therapy in human asthma cases.

Extracellular Vesicles in Pathophysiology: A Prudent Target That Requires Careful Consideration

Extracellular vesicles (EVs) are membrane-bound particles released by cells to perform multitudes of biological functions. Owing to their significant implications in diseases, the pathophysiological role of EVs continues to be extensively studied, leading research to neglect the need to explore their role in normal physiology. Despite this, many identified physiological functions of EVs, including, but not limited to, tissue repair, early development and aging, are attributed to their modulatory role in various signaling pathways via intercellular communication. EVs are widely perceived as a potential therapeutic strategy for better prognosis, primarily through utilization as a mode of delivery vehicle. Moreover, disease-associated EVs serve as candidates for the targeted inhibition by pharmacological or genetic means. However, these attempts are often accompanied by major challenges, such as off-target effects, which may result in adverse phenotypes. This renders the clinical efficacy of EVs elusive, indicating that further understanding of the specific role of EVs in physiology may enhance their utility. This review highlights the essential role of EVs in maintaining cellular homeostasis under different physiological settings, and also discusses the various aspects that may potentially hinder the robust utility of EV-based therapeutics.

Lipidic Nanoparticles, Extracellular Vesicles and Hybrid Platforms as Advanced Medicinal Products: Future Therapeutic Prospects for Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, affect a wide variety of the population and pose significant challenges with progressive and irreversible neural cell loss. The limitations of brain-targeting therapies and the unclear molecular mechanisms driving neurodegeneration hamper the possibility of developing successful treatment options. Thus, nanoscale drug delivery platforms offer a promising solution. This paper explores and compares lipidic nanoparticles, extracellular vesicles (EVs), and hybrid liposomal-EV nanoplatforms as advanced approaches for targeted delivery to combat neurodegeneration. Lipidic nanoparticles are well-characterized platforms that allow multi-drug loading and scalable production. Conversely, EVs offer the ability of selectively targeting specific tissues and high biocompatibility. The combination of these two platforms in one could lead to promising results in the treatment of neurodegeneration. However, many issues, such as the regulatory framework, remain to be solved before these novel products are translated into clinical practice.

The Role of Extracellular Vesicles in SARS-CoV-2-Induced Acute Kidney Injury: An Overview

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected millions worldwide since its outbreak in the winter of 2019. While extensive research has primarily focused on the deleterious respiratory effects of SARS-CoV-2 in recent years, its pan-tropism has become evident. Among the vital organs susceptible to SARS-CoV-2 infection is the kidney. Post SARS-CoV-2 infection, patients have developed coronavirus disease 19 (COVID-19), with reported incidences of COVID-19 patients developing acute kidney injury (AKI). Given COVID-19's multisystemic manifestation, our review focuses on the impact of SARS-CoV-2 infection within the renal system with an emphasis on the current hypotheses regarding the role of extracellular vesicles (EVs) in SARS-CoV-2 pathogenesis. Emerging studies have shown that SARS-CoV-2 can directly infect the kidney, whereas EVs are involved in the spreading of SARS-CoV-2 particles to other neighboring cells. Once the viral particles are within the kidney system, many proinflammatory signaling pathways are shown to be activated, resulting in AKI. Hence, clinical investigation of urinary proinflammatory components and total urinary extracellular vesicles (uEVs) with viral particles have been used to assess the severity of AKI in patients with COVID-19. Remarkedly, new emerging studies have shown the potential of mesenchymal stem cell-derived EVs (MSC-EVs) and ACE2-containing EVs as a hopeful therapeutic tool to inhibit SARS-CoV-2 RNA replication and block viral entry, respectively. Overall, understanding EVs' physiological role is crucial and hopefully will rejuvenate our therapeutic approach towards COVID-19 patients with AKI.

Extracellular Vesicles in Liver Transplantation: Current Evidence and Future Challenges

Extracellular vesicles (EVs) are emerging as a promising field of research in liver disease. EVs are small, membrane-bound vesicles that contain various bioactive molecules, such as proteins, lipids, and nucleic acids and are involved in intercellular communication. They have been implicated in numerous physiological and pathological processes, including immune modulation and tissue repair, which make their use appealing in liver transplantation (LT). This review summarizes the current state of knowledge regarding the role of EVs in LT, including their potential use as biomarkers and therapeutic agents and their role in graft rejection. By providing a comprehensive insight into this emerging topic, this research lays the groundwork for the potential application of EVs in LT.

Physiologically Based Pharmacokinetic Modeling of Extracellular Vesicles

Extracellular vesicles (EVs) are lipid membrane bound-cell-derived structures that are a key player in intercellular communication and facilitate numerous cellular functions such as tumor growth, metastasis, immunosuppression, and angiogenesis. They can be used as a drug delivery platform because they can protect drugs from degradation and target specific cells or tissues. With the advancement in the technologies and methods in EV research, EV-therapeutics are one of the fast-growing domains in the human health sector. Therapeutic translation of EVs in clinics requires assessing the quality, safety, and efficacy of the EVs, in which pharmacokinetics is very crucial. We report here the application of physiologically based pharmacokinetic (PBPK) modeling as a principal tool for the prediction of absorption, distribution, metabolism, and excretion of EVs. To create a PBPK model of EVs, researchers would need to gather data on the size, shape, and composition of the EVs, as well as the physiological processes that affect their behavior in the body. The PBPK model would then be used to predict the pharmacokinetics of drugs delivered via EVs, such as the rate at which the drug is absorbed and distributed throughout the body, the rate at which it is metabolized and eliminated, and the maximum concentration of the drug in the body. This information can be used to optimize the design of EV-based drug delivery systems, including the size and composition of the EVs, the route of administration, and the dose of the drug. There has not been any dedicated review article that describes the PBPK modeling of EV. This review provides an overview of the absorption, distribution, metabolism, and excretion (ADME) phenomena of EVs. In addition, we will briefly describe the different computer-based modeling approaches that may help in the future of EV-based therapeutic research.

Peptide-Based Therapeutic HPV Cancer Vaccine Synthesized via Bacterial Outer Membrane Vesicles

Background

Peptide-based vaccines have broad application prospects because of their safety, simple preparation, and effectiveness, especially in the development of personalized cancer vaccines, which have shown great advantages. However, the current peptide-based vaccines often require artificial synthesis and intricate delivery technology, which increases the cost and complexity of preparation.

Methods

Here, we developed a simple technique for combining a peptide and a delivery system using the natural secretion system of bacteria. Specifically, we biosynthesized an antigenic peptide in bacteria, which was then extracellularly released through the bacterial secretory vesicles, thus simultaneously achieving the biosynthesis and delivery of the peptide.

Results

The system utilizes the natural properties of bacterial vesicles to promote antigen uptake and dendritic cell (DC) maturation. Therefore, tumor-specific CD4+ Th1 and CD8+ cytotoxic T lymphocyte (CTL) responses were induced in TC-1 tumor-bearing mice, thereby efficiently suppressing tumor growth.

Conclusion

This research promotes innovation and extends the application of peptide-based vaccine biosynthesis technology. Importantly, it provides a new method for personalized cancer immunotherapy that uses screened peptides as antigens in the future.

Biodistribution of Intratracheal, Intranasal, and Intravenous Injections of Human Mesenchymal Stromal Cell-Derived Extracellular Vesicles in a Mouse Model for Drug Delivery Studies

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) are extensively studied as therapeutic tools. Evaluation of their biodistribution is fundamental to understanding MSC-EVs' impact on target organs. In our work, MSC-EVs were initially labeled with DiR, a fluorescent lipophilic dye, and administered to BALB/c mice (2.00 × 10¹⁰ EV/mice) through the following routes: intravenous (IV), intratracheal (IT) and intranasal (IN). DiR-labeled MSC-EVs were monitored immediately after injection, and after 3 and 24 hours (h). Whole-body analysis, 3 h after IV injection, showed an accumulation of MSC-EVs in the mice abdominal region, compared to IT and IN, where EVs mainly localized at the levels of the chest and brain region, respectively. After 24 h, EV-injected mice retained a stronger positivity in the same regions identified after 3 h from injection. The analyses of isolated organs confirmed the accumulation of EVs in the spleen and liver after IV administration. Twenty-four hours after the IT injection of MSC-EVs, a stronger positivity was detected selectively in the isolated lungs, while for IN, the signal was confined to the brain. In conclusion, these results show that local administration of EVs can increase their concentration in selective organs, limiting their systemic biodistribution and possibly the extra-organ effects. Biodistribution studies can help in the selection of the most appropriate way of administration of MSC-EVs for the treatment of different diseases.