Drug Delivery to the Bone Microenvironment Mediated by Exosomes: An Axiom or Enigma

Surface Engineered Osteoblast-Extracellular Vesicles Serve as an Efficient Carrier for Drug and Small RNA to Actively Target Osteosarcoma

Osteosarcoma (OS) is a rare malignant tumor that affects soft tissue and has high rates of lung metastasis and mortality. The primary treatments for OS include preoperative chemotherapy, surgical resection of the lesion, and postoperative chemotherapy. However, OS chemotherapy presents critical challenges related to treatment toxicity and multiple drug resistance. To address these challenges, nanotechnology has developed nanosystems that release drugs directly to OS cells, reducing the drug's toxicity. Extracellular vesicles (EVs) are nanosized lipid-bilayer bound vesicles that act as cell-derived vehicles and drug delivery systems for several cancers. This study aims to utilize EVs for OS management by co-delivering Hdac1 siRNA and zoledronic acid (zol). The EVs' surface is modified with folic acid (FA) and their targeting ability is compared to that of native EVs. The results showed that the EVs' targeting ability depends on the parent cell source, and FA conjugation further enhanced it. Furthermore, EVs were used as the carrier for co-loading drug (zol) and small RNA (Hdac-1). This approach of using surface engineered EVs as carriers for cargo loading and delivery can be a promising strategy for osteosarcoma management.

Synergistic Interaction between Polysaccharide-Based Extracellular Matrix and Mineralized Osteoblast-Derived EVs Promotes Bone Regeneration via miRNA-mRNA Regulatory Axis

Extracellular vesicles (EVs) derived from bone progenitor cells are advantageous as cell-free and non-immunogenic cargo delivery vehicles. In this study, EVs are isolated from MC3T3-E1 cells before (GM-EVs) and after mineralization for 7 and 14 days (DM-EVs). It was observed that DM-EVs accelerate the process of differentiation in recipient cells more prominently. The small RNA sequencing of EVs revealed that miR-204-5p, miR-221-3p, and miR-148a-3p are among the highly upregulated miRNAs that have an inhibitory effect on the function of mRNAs, Sox11, Timp3, and Ccna2 in host cells, which is probably responsible for enhancing the activity of osteoblastic genes. To enhance the bioavailability of EVs, they are encapsulated in a chitosan-collagen composite hydrogel that serves as a bioresorbable extracellular matrix (ECM). The EVs-integrated scaffold (DM-EVs + Scaffold) enhances bone regeneration in critical-sized calvarial bone defects in rats within 8 weeks of implantation by providing the ECM cues. The shelf life of DM-EVs + Scaffold indicates that the bioactivity of EVs and their cargo in the polymer matrix remains intact for up to 30 days. Integrating mineralized cell-derived EVs into an ECM represents a bioresorbable matrix with a cell-free method for promoting new bone formation through the miRNA-mRNA regulatory axis.

Role of miRNA-regulated type H vessel formation in osteoporosis

Osteoporosis (OP) is a chronic systemic bone metabolism disease characterized by decreased bone mass, microarchitectural deterioration, and fragility fractures. With the demographic change caused by long lifespans and population aging, OP is a growing health problem. The role of miRNA in the pathogenesis of OP has also attracted widespread attention from scholars in recent years. Type H vessels are unique microvessels of the bone and have become a new focus in the pathogenesis of OP because they play an essential role in osteogenesis-angiogenesis coupling. Previous studies found some miRNAs regulate type H vessel formation through the regulatory factors, including platelet-derived growth factor-BB (PDGF-BB), hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), and so on. These findings help us gain a more in-depth understanding of the relationship among miRNAs, type H vessels, and OP to find a new perspective on treating OP. In the present mini-review, we will introduce the role of type H vessels in the pathogenesis of OP and the regulation of miRNAs on type H vessel formation by affecting regulatory factors to provide some valuable insights for future studies of OP treatment.

Canine Mesenchymal Stromal Cell Exosomes: State-of-the-Art Characterization, Functional Analysis and Applications in Various Diseases

Canine mesenchymal stromal cells (MSCs) possess the capacity to differentiate into a variety of cell types and secrete a wide range of bioactive molecules in the form of soluble and membrane-bound exosomes. Extracellular vesicles/exosomes are nano-sized vesicles that carry proteins, lipids, and nucleic acids and can modulate recipient cell response in various ways. The process of exosome formation is a physiological interaction between cells. With a significant increase in basic research over the last two decades, there has been a tremendous expansion in research in MSC exosomes and their potential applications in canine disease models. The characterization of exosomes has demonstrated considerable variations in terms of source, culture conditions of MSCs, and the inclusion of fetal bovine serum or platelet lysate in the cell cultures. Furthermore, the amalgamation of exosomes with various nano-materials has become a novel approach to the fabrication of nano-exosomes. The fabrication of exosomes necessitates the elimination of extrinsic proteins, thus enhancing their potential therapeutic uses in a variety of disease models, including spinal cord injury, osteoarthritis, and inflammatory bowel disease. This review summarizes current knowledge on the characteristics, biological functions, and clinical relevance of canine MSC exosomes and their potential use in human and canine research. As discussed, exosomes have the ability to control lethal vertebrate diseases by administration directly at the injury site or through specific drug delivery mechanisms.

Mesenchymal stem cell-derived exosomes: Shaping the next era of stroke treatment

Exosome-based treatments are gaining traction as a viable approach to addressing the various issues faced by an ischemic stroke. These extracellular vesicles, mainly produced by Mesenchymal Stem Cells (MSCs), exhibit many properties with substantial therapeutic potential. Exosomes are particularly appealing for stroke therapy because of their low immunogenicity, effective cargo transport, and ability to cross the blood-brain barrier. Their diverse effects include neuroprotection, angiogenesis stimulation, inflammatory response modulation, and cell death pathway attenuation, synergistically promoting neuronal survival, tissue regeneration, and functional recovery. Exosomes also show potential as diagnostic indicators for early stroke identification and customized treatment options. Despite these promising qualities, current exosome-based therapeutics have some limitations. The heterogeneity of exosome release among cell types, difficulty in standardization and isolation techniques, and complications linked to dosage and targeted administration necessitates extensive investigation. It is critical to thoroughly understand exosomal processes and their complicated interactions within the cellular milieu. To improve the practicality and efficacy of exosome-based medicines, research efforts must focus on improving production processes, developing robust evaluation criteria, and developing large-scale isolation techniques. Altogether, exosomes' multifunctional properties offer a new route for transforming stroke treatment and significantly improving patient outcomes.

Engineered exosomes for tissue regeneration: from biouptake, functionalization and biosafety to applications

Exosomes are increasingly recognized as important effector molecules that regulate intercellular signaling pathways. Notably, certain types of exosomes can induce therapeutic responses, including cell proliferation, angiogenesis, and tissue repair. The use of exosomes in therapy is a hot spot in current research, especially in regenerative medicine. Despite the therapeutic potential, problems have hindered their success in clinical applications. These shortcomings include low concentration, poor targeting and limited loading capability. To fully realize their therapeutic potential, certain modifications are needed in native exosomes. In the present review, we summarize the exosome modification and functionalization strategies. In addition, we provide an overview of potential clinical applications and highlight the issues associated with the biosafety and biocompatibility of engineered exosomes in applications.

17β-Estradiol-Loaded Exosomes for Targeted Drug Delivery in Osteoporosis: A Comparative Study of Two Loading Methods

Purpose

Exosomes are natural nanoparticles that participate in intercellular communication through molecular transport. Recently, due to their membrane vesicular structure and surface proteins, exosomes have been used extensively in the research field of drug delivery. Osteoporosis is an inflammation in which the cellular balance of bone tissue is disturbed that reduces bone density and making bone prone to abnormal fractures with small amount of force. Utilizing estrogen is one of the main therapeutic strategies for osteoporosis. Despite the positive effects of estrogen on bone tissue, changes in the natural estrogen levels of the body can cause a number of diseases such as different types of cancer. Therefore, designing a therapeutic system which controls more accurate tissue targeting of estrogen seems to be a rational and promising practical approach.

Methods

In this study, bone marrow mesenchymal stem cells (BMMSCs)-derived exosomes were loaded by estradiol using two different methods of drug loading, namely incubation and sonication methods and then the survival effects of the drug loaded exosomes on BMMSCs was investigated.

Results

Examination of size, shape, and surface factors of exosomes in different states (pure exosomes and drug-loaded exosomes) showed that the round morphology of exosomes was preserved in all conditions. However, the particles size increased significantly when loaded by sonication method. The increased survival of BMMSCs was noted with estradiol-loaded exosomes when compared to the control group.

Conclusion

The results suggest that estradiol-loaded exosomes have potential to be used as nano-drug carriers in the treatment of osteoporosis.

Engineering exosomes and biomaterial-assisted exosomes as therapeutic carriers for bone regeneration

Mesenchymal stem cell-based therapy has become an effective therapeutic approach for bone regeneration. However, there are still limitations in successful clinical translation. Recently, the secretome of mesenchymal stem cells, especially exosome, plays a critical role in promoting bone repair and regeneration. Exosomes are nanosized, lipid bilayer-enclosed structures carrying proteins, lipids, RNAs, metabolites, growth factors, and cytokines and have attracted great attention for their potential application in bone regenerative medicine. In addition, preconditioning of parental cells and exosome engineering can enhance the regenerative potential of exosomes for treating bone defects. Moreover, with recent advancements in various biomaterials to enhance the therapeutic functions of exosomes, biomaterial-assisted exosomes have become a promising strategy for bone regeneration. This review discusses different insights regarding the roles of exosomes in bone regeneration and summarizes the applications of engineering exosomes and biomaterial-assisted exosomes as safe and versatile bone regeneration agent delivery platforms. The current hurdles of transitioning exosomes from bench to bedside are also discussed.

Exosomes-Based Nanomedicine for Neurodegenerative Diseases: Current Insights and Future Challenges

Neurodegenerative diseases constitute a group of pathologies whose etiology remains unknown in many cases, and there are no treatments that stop the progression of such diseases. Moreover, the existence of the blood-brain barrier is an impediment to the penetration of exogenous molecules, including those found in many drugs. Exosomes are extracellular vesicles secreted by a wide variety of cells, and their primary functions include intercellular communication, immune responses, human reproduction, and synaptic plasticity. Due to their natural origin and molecular similarities with most cell types, exosomes have emerged as promising therapeutic tools for numerous diseases. Specifically, neurodegenerative diseases have shown to be a potential target for this nanomedicine strategy due to the difficult access to the brain and the strategy's pathophysiological complexity. In this regard, this review explores the most important biological-origin drug delivery systems, innovative isolation methods of exosomes, their physicochemical characterization, drug loading, cutting-edge functionalization strategies to target them within the brain, the latest research studies in neurodegenerative diseases, and the future challenges of exosomes as nanomedicine-based therapeutic tools.

Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Accelerate Functional Recovery After Spinal Cord Injury by Promoting the Phagocytosis of Macrophages to Clean Myelin Debris

Macrophage phagocytosis contributes predominantly to processing central nervous system (CNS) debris and further facilitates neurological function restoration after CNS injury. The aims of this study were to evaluate the effect of bone marrow mesenchymal stem cells (BMSC)-derived exosomes (BMSC-Exos) on the phagocytic capability of macrophages to clear myelin debris and to investigate the underlying molecular mechanism during the spinal cord injury (SCI) process. This work reveals that monocyte-derived macrophages (MDMs) infiltrating into the SCI site could efficiently engulf myelin debris and process phagocytic material. However, the phagocytic ability of macrophages to clear tissue debris is compromised after SCI. The administration of BMSC-Exos as an approach for SCI treatment could rescue macrophage normal function by improving the phagocytic capability of myelin debris internalization, which is beneficial for SCI repair, as evidenced by better axon regrowth and increased hindlimb locomotor functional recovery in a rodent model. Examination of macrophage treatment with BMSC-Exos revealed that BMSC-Exos could promote the capacity of macrophages to phagocytose myelin debris in vitro and could create a regenerative microenvironment for axon regrowth. In addition, we confirmed that BMSC-Exo treatment resulted in improved phagocytosis of engulfed myelin debris by promoting the expression of macrophage receptor with collagenous structure (MARCO) in macrophages. The inhibition of MARCO with PolyG (a MARCO antagonist) impaired the effect of BMSC-Exos on the phagocytic capacity of macrophages and resulted in compromised myelin clearance at the lesion site, leading to further tissue damage and impaired functional healing after SCI. In conclusion, these data indicated that targeting the phagocytic ability of macrophages may have therapeutic potential for the improvement in functional healing after SCI. The administration of BMSC-Exos as a cell-free immune therapy strategy has wide application prospects for SCI treatment.

Extracellular Vesicles in Osteosarcoma: Antagonists or Therapeutic Agents?

Osteosarcoma (OS) is a skeletal tumor affecting mainly children and adolescents. The presence of distance metastasis is frequent and it is localized preferentially to the lung, representing the main reason for death among patients. The therapeutic approaches are based on surgery and chemotherapeutics. However, the drug resistance and the side effects associated with the chemotherapy require the identification of new therapeutic approaches. The understanding of the complex biological scenario of the osteosarcoma will open the way for the identification of new targets for its treatment. Recently, a great interest of scientific community is for extracellular vesicles (EVs), that are released in the tumor microenvironment and are important regulators of tumor proliferation and the metastatic process. At the same time, circulating extracellular vesicles can be exploited as diagnostic and prognostic biomarkers, and they can be loaded with drugs as a new therapeutic approach for osteosarcoma patients. Thus, the characterization of OS-related EVs could represent a way to convert these vesicles from antagonists for human health into therapeutic and/or diagnostic agents.

Small Extracellular Vesicles in the Development, Diagnosis, and Possible Therapeutic Application of Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) persists among the most lethal and broad-spreading malignancies in China. The exosome is a kind of extracellular vesicle (EV) from about 30 to 200 nm in diameter, contributing to the transfer of specific functional molecules, such as metabolites, proteins, lipids, and nucleic acids. The paramount role of exosomes in the formation and development of ESCC, which relies on promoting intercellular communication in the tumor microenvironment (TME), is manifested with immense amounts. Tumor-derived exosomes (TDEs) participate in most hallmarks of ESCC, including tumorigenesis, invasion, angiogenesis, immunologic escape, metastasis, radioresistance, and chemoresistance. Published reports have delineated that exosome-encapsulated cargos like miRNAs may have utility in the diagnosis, as prognostic biomarkers, and in the treatment of ESCC. This review summarizes the function of exosomes in the neoplasia, progression, and metastasis of ESCC, which improves our understanding of the etiology and pathogenesis of ESCC, and presents a promising target for early diagnostics in ESCC. However, recent studies of exosomes in the treatment of ESCC are sparse. Thus, we introduce the advances in exosome-based methods and indicate the possible applications for ESCC therapy in the future.