Extracellular Vesicle Heterogeneity and Its Impact for Regenerative Medicine Applications

Extracellular Vesicle Preparation and Analysis: A State-of-the-Art Review

In recent decades, research on Extracellular Vesicles (EVs) has gained prominence in the life sciences due to their critical roles in both health and disease states, offering promising applications in disease diagnosis, drug delivery, and therapy. However, their inherent heterogeneity and complex origins pose significant challenges to their preparation, analysis, and subsequent clinical application. This review is structured to provide an overview of the biogenesis, composition, and various sources of EVs, thereby laying the groundwork for a detailed discussion of contemporary techniques for their preparation and analysis. Particular focus is given to state-of-the-art technologies that employ both microfluidic and non-microfluidic platforms for EV processing. Furthermore, this discourse extends into innovative approaches that incorporate artificial intelligence and cutting-edge electrochemical sensors, with a particular emphasis on single EV analysis. This review proposes current challenges and outlines prospective avenues for future research. The objective is to motivate researchers to innovate and expand methods for the preparation and analysis of EVs, fully unlocking their biomedical potential.

Role of aptamer technology in extracellular vesicle biology and therapeutic applications

Extracellular vesicles (EVs) are cell-derived nanosized membrane-bound vesicles that are important intercellular signalling regulators in local cell-to-cell and distant cell-to-tissue communication. Their inherent capacity to transverse cell membranes and transfer complex bioactive cargo reflective of their cell source, as well as their ability to be modified through various engineering and modification strategies, have attracted significant therapeutic interest. Molecular bioengineering strategies are providing a new frontier for EV-based therapy, including novel mRNA vaccines, antigen cross-presentation and immunotherapy, organ delivery and repair, and cancer immune surveillance and targeted therapeutics. The revolution of EVs, their diversity as biocarriers and their potential to contribute to intercellular communication, is well understood and appreciated but is ultimately dependent on the development of methods and techniques for their isolation, characterization and enhanced targeting. As single-stranded oligonucleotides, aptamers, also known as chemical antibodies, offer significant biological, chemical, economic, and therapeutic advantages in terms of their size, selectivity, versatility, and multifunctional programming. Their integration into the field of EVs has been contributing to the development of isolation, detection, and analysis pipelines associated with bioengineering strategies for nano-meets-molecular biology, thus translating their use for therapeutic and diagnostic utility.

The role of extracellular vesicle immune checkpoints in cancer

Immune checkpoints (ICPs) play a crucial role in regulating the immune response. In the tumor, malignant cells can hijack the immunosuppressive effects of inhibitory ICPs to promote tumor progression. Extracellular vesicles (EVs) are produced by a variety of cells and contain bioactive molecules on their surface or within their lumen. The expression of ICPs has also been detected in EVs. In vitro and in vivo studies have shown that extracellular vesicle immune checkpoints (EV ICPs) have immunomodulatory effects and are involved in tumor immunity. EV ICPs isolated from the peripheral blood of cancer patients are closely associated with the tumor progression and the prognosis of cancer patients. Blocking inhibitory ICPs has been recognized as an effective strategy in cancer treatment. However, the efficacy of immune checkpoint inhibitors (ICIs) in cancer treatment is hindered by the emergence of therapeutic resistance, which limits their widespread use. Researchers have demonstrated that EV ICPs are correlated with clinical response to ICIs therapy and were involved in therapeutic resistance. Therefore, it is essential to investigate the immunomodulatory effects, underlying mechanisms, and clinical significance of EV ICPs in cancer. This review aims to comprehensively explore these aspects. We have provided a comprehensive description of the cellular origins, immunomodulatory effects, and clinical significance of EV ICPs in cancer, based on relevant studies.

Full-length tRNAs lacking a functional CCA tail are selectively sorted into the lumen of extracellular vesicles

Small extracellular vesicles (sEVs) are heterogenous lipid membrane particles typically less than 200 nm in size and secreted by most cell types either constitutively or upon activation signals. sEVs isolated from biofluids contain RNAs, including small non-coding RNAs (ncRNAs), that can be either encapsulated within the EV lumen or bound to the EV surface. EV-associated microRNAs (miRNAs) are, despite a relatively low abundance, extensively investigated for their selective incorporation and their role in cell-cell communication. In contrast, the sorting of highly-structured ncRNA species is understudied, mainly due to technical limitations of traditional small RNA sequencing protocols. Here, we adapted ALL-tRNAseq to profile the relative abundance of highly structured and potentially methylated small ncRNA species, including transfer RNAs (tRNAs), small nucleolar RNAs (snoRNAs), and Y RNAs in bulk EV preparations. We determined that full-length tRNAs, typically 75 to 90 nucleotides in length, were the dominant small ncRNA species (>60% of all reads in the 18-120 nucleotides size-range) in all cell culture-derived EVs, as well as in human plasma-derived EV samples, vastly outnumbering 21 nucleotides-long miRNAs. Nearly all EV-associated tRNAs were protected from external RNAse treatment, indicating a location within the EV lumen. Strikingly, the vast majority of luminal-sorted, full-length, nucleobase modification-containing EV-tRNA sequences, harbored a dysfunctional 3' CCA tail, 1 to 3 nucleotides truncated, rendering them incompetent for amino acid loading. In contrast, in non-EV associated extracellular particle fractions (NVEPs), tRNAs appeared almost exclusively fragmented or 'nicked' into tRNA-derived small RNAs (tsRNAs) with lengths between 18 to 35 nucleotides. We propose that in mammalian cells, tRNAs that lack a functional 3' CCA tail are selectively sorted into EVs and shuttled out of the producing cell, offering a new perspective into the physiological role of secreted EVs and luminal cargo-selection.

Outer Membrane Vesicles Released from Garlic Exosome-like Nanoparticles (GaELNs) Train Gut Bacteria that Reverses Type 2 Diabetes via the Gut-Brain Axis

Gut microbiota function has numerous effects on humans and the diet humans consume has emerged as a pivotal determinant of gut microbiota function. Here, a new concept that gut microbiota can be trained by diet-derived exosome-like nanoparticles (ELNs) to release healthy outer membrane vesicles (OMVs) is introduced. Specifically, OMVs released from garlic ELN (GaELNs) trained human gut Akkermansia muciniphila (A. muciniphila) can reverse high-fat diet-induced type 2 diabetes (T2DM) in mice. Oral administration of OMVs released from GaELNs trained A. muciniphila can traffick to the brain where they are taken up by microglial cells, resulting in inhibition of high-fat diet-induced brain inflammation. GaELNs treatment increases the levels of OMV Amuc-1100, P9, and phosphatidylcholines. Increasing the levels of Amuc-1100 and P9 leads to increasing the GLP-1 plasma level. Increasing the levels of phosphatidylcholines is required for inhibition of cGas and STING-mediated inflammation and GLP-1R crosstalk with the insulin pathway that leads to increasing expression of Insulin Receptor Substrate (IRS1 and IRS2) on OMV targeted cells. These findings reveal a molecular mechanism whereby OMVs from plant nanoparticle-trained gut bacteria regulate genes expressed in the brain, and have implications for the treatment of brain dysfunction caused by a metabolic syndrome.

Advanced Nanoencapsulation-Enabled Ultrasensitive Analysis: Unraveling Tumor Extracellular Vesicle Subpopulations for Differential Diagnosis of Hepatocellular Carcinoma via DNA Cascade Reactions

Tumor-derived extracellular vesicles (tEVs) hold immense promise as potential biomarkers for the precise diagnosis of hepatocellular carcinoma (HCC). However, their clinical translation is hampered by their inherent characteristics, such as small size and high heterogeneity and complex environment, including non-EV particles and normal cell-derived EVs, which prolong separation procedures and compromise detection accuracy. In this study, we devised a DNA cascade reaction-triggered individual EV nanoencapsulation (DCR-IEVN) strategy to achieve the ultrasensitive and specific detection of tEV subpopulations via routine flow cytometry in a one-pot, one-step fashion. DCR-IEVN enables the direct and selective packaging of multiple tEV subpopulations in clinical serum samples into flower-like particles exceeding 600 nm. This approach bypasses the need for EV isolation, effectively reducing interference from non-EV particles and nontumor EVs. Compared with conventional analytical technologies, DCR-IEVN exhibits superior efficacy in diagnosing HCC owing to its high selectivity for tEVs. Integration of machine learning algorithms with DCR-IEVN resulted in differential diagnosis accuracy of 96.7% for the training cohort (n = 120) and 93.3% for the validation cohort (n = 30), effectively distinguishing HCC, cirrhosis, and healthy donors. This strategy offers a streamlined workflow and rapid assay completion and requires only small-volume serum samples and routine clinical devices, facilitating the clinical translation of tEV-based tumor diagnosis.

A roadmap towards manufacturing extracellular vesicles for cardiac repair

For the past two decades researchers have linked extracellular vesicle (EV)-mediated mechanisms to various physiological and pathological processes in the heart, such as immune response regulation, fibrosis, angiogenesis, and the survival and growth of cardiomyocytes. Although use of EVs has gathered momentum in the cardiac field, several obstacles in both upstream and downstream processes during EV manufacture need to be addressed before clinical success can be achieved. Low EV yields obtained in small-scale cultures deter clinical translation, as mass production is a prerequisite to meet therapeutic doses. Moreover, standardizing EV manufacture is critical given the inherent heterogeneity of EVs and the constraints of current isolation techniques. In this review, we discuss the critical steps for the large-scale manufacturing of high-potency EVs for cardiac therapies.

Extracellular Vesicle-Related Non-Coding RNAs in Hepatocellular Carcinoma: An Overview

Hepatocellular carcinoma (HCC) is the most common primary liver cancer. It is a major public health problem worldwide, and it is often diagnosed at advanced stages, when no effective treatment options are available. Extracellular vesicles (EVs) are nanosized double-layer lipid vesicles containing various biomolecule cargoes, such as lipids, proteins, and nucleic acids. EVs are released from nearly all types of cells and have been shown to play an important role in cell-to-cell communication. In recent years, many studies have investigated the role of EVs in cancer, including HCC. Emerging studies have shown that EVs play primary roles in the development and progression of cancer, modulating tumor growth and metastasis formation. Moreover, it has been observed that non-coding RNAs (ncRNAs) carried by tumor cell-derived EVs promote tumorigenesis, regulating the tumor microenvironment (TME) and playing critical roles in the progression, angiogenesis, metastasis, immune escape, and drug resistance of HCC. EV-related ncRNAs can provide information regarding disease status, thus encompassing a role as biomarkers. In this review, we discuss the main roles of ncRNAs present in HCC-derived EVs, including micro(mi) RNAs, long non-coding (lnc) RNAs, and circular (circ) RNAs, and their potential clinical value as biomarkers and therapeutic targets.

Immune cell-derived extracellular vesicles for precision therapy of inflammatory-related diseases

Inflammation-related diseases impose a significant global health burden, necessitating urgent exploration of novel treatment modalities for improved clinical outcomes. We begin by discussing the limitations of conventional approaches and underscore the pivotal involvement of immune cells in the inflammatory process. Amidst the rapid growth of immunology, the therapeutic potential of immune cell-derived extracellular vesicles (EVs) has garnered substantial attention due to their capacity to modulate inflammatory response. We provide an in-depth examination of immune cell-derived EVs, delineating their promising roles across diverse disease conditions in both preclinical and clinical settings. Additionally, to direct the development of the next-generation drug delivery systems, we comprehensively investigate the engineered EVs on their advanced isolation methods, cargo loading techniques, and innovative engineering strategies. This review ends with a focus on the prevailing challenges and considerations regarding the clinical translation of EVs in future, emphasizing the need of standardized characterization and scalable production processes. Ultimately, immune cell-derived EVs represent a cutting-edge therapeutic approach and delivery platform, holding immense promise in precision medicine.

Regulation of Oxygen Tension as a Strategy to Control Chondrocytic Phenotype for Cartilage Tissue Engineering and Regeneration

Cartilage defects and osteoarthritis are health problems which are major burdens on health care systems globally, especially in aging populations. Cartilage is a vulnerable tissue, which generally faces a progressive degenerative process when injured. This makes it the 11th most common cause of global disability. Conservative methods are used to treat the initial phases of the illness, while orthopedic management is the method used for more progressed phases. These include, for instance, arthroscopic shaving, microfracturing and mosaicplasty, and joint replacement as the final treatment. Cell-based implantation methods have also been developed. Despite reports of successful treatments, they often suffer from the non-optimal nature of chondrocyte phenotype in the repair tissue. Thus, improved strategies to control the phenotype of the regenerating cells are needed. Avascular tissue cartilage relies on diffusion for nutrients acquisition and the removal of metabolic waste products. A low oxygen content is also present in cartilage, and the chondrocytes are, in fact, well adapted to it. Therefore, this raises an idea that the regulation of oxygen tension could be a strategy to control the chondrocyte phenotype expression, important in cartilage tissue for regenerative purposes. This narrative review discusses the aspects related to oxygen tension in the metabolism and regulation of articular and growth plate chondrocytes and progenitor cell phenotypes, and the role of some microenvironmental factors as regulators of chondrocytes.

Microenvironment Remodeling Self-Healing Hydrogel for Promoting Flap Survival

Random flap grafting is a routine procedure used in plastic and reconstructive surgery to repair and reconstruct large tissue defects. Flap necrosis is primarily caused by ischemia-reperfusion injury and inadequate blood supply to the distal flap. Ischemia-reperfusion injury leads to the production of excessive reactive oxygen species, creating a pathological microenvironment that impairs cellular function and angiogenesis. In this study, we developed a microenvironment remodeling self-healing hydrogel [laminarin-chitosan-based hydrogel-loaded extracellular vesicles and ceria nanozymes (LCH@EVs&CNZs)] to improve the flap microenvironment and synergistically promote flap regeneration and survival. The natural self-healing hydrogel (LCH) was created by the oxidation laminarin and carboxymethylated chitosan via a Schiff base reaction. We loaded this hydrogel with CNZs and EVs. CNZs are a class of nanomaterials with enzymatic activity known for their strong scavenging capacity for reactive oxygen species, thus alleviating oxidative stress. EVs are cell-secreted vesicular structures containing thousands of bioactive substances that can promote cell proliferation, migration, differentiation, and angiogenesis. The constructed LCH@EVs&CNZs demonstrated a robust capacity for scavenging excess reactive oxygen species, thereby conferring cellular protection in oxidative stress environments. Moreover, these constructs notably enhance cell migration and angiogenesis. Our results demonstrate that LCH@EVs&CNZs effectively remodel the pathological skin flap microenvironment and marked improve flap survival. This approach introduces a new therapeutic strategy combining microenvironmental remodeling with EV therapy, which holds promise for promoting flap survival.

Exosome lncRNA IFNG-AS1 derived from mesenchymal stem cells of human adipose ameliorates neurogenesis and ASD-like behavior in BTBR mice

BACKGROUND

The transplantation of exosomes derived from human adipose-derived mesenchymal stem cells (hADSCs) has emerged as a prospective cellular-free therapeutic intervention for the treatment of neurodevelopmental disorders (NDDs), as well as autism spectrum disorder (ASD). Nevertheless, the efficacy of hADSC exosome transplantation for ASD treatment remains to be verified, and the underlying mechanism of action remains unclear.

RESULTS

The exosomal long non-coding RNAs (lncRNAs) from hADSC and human umbilical cord mesenchymal stem cells (hUCMSC) were sequenced and 13,915 and 729 lncRNAs were obtained, respectively. The lncRNAs present in hADSC-Exos encompass those found in hUCMSC-Exos and are associated with neurogenesis. The biodistribution of hADSC-Exos in mouse brain ventricles and organoids was tracked, and the cellular uptake of hADSC-Exos was evaluated both in vivo and in vitro. hADSC-Exos promote neurogenesis in brain organoid and ameliorate social deficits in ASD mouse model BTBR T + tf/J (BTBR). Fluorescence in situ hybridization (FISH) confirmed lncRNA Ifngas1 significantly increased in the prefrontal cortex (PFC) of adult mice after hADSC-Exos intraventricular injection. The lncRNA Ifngas1 can act as a molecular sponge for miR-21a-3p to play a regulatory role and promote neurogenesis through the miR-21a-3p/PI3K/AKT axis.

CONCLUSION

We demonstrated hADSC-Exos have the ability to confer neuroprotection through functional restoration, attenuation of neuroinflammation, inhibition of neuronal apoptosis, and promotion of neurogenesis both in vitro and in vivo. The hADSC-Exos-derived lncRNA IFNG-AS1 acts as a molecular sponge and facilitates neurogenesis via the miR-21a-3p/PI3K/AKT signaling pathway, thereby exerting a regulatory effect. Our findings suggest a potential therapeutic avenue for individuals with ASD.

Tumor immune escape: extracellular vesicles roles and therapeutics application

BACKGROUND

Immune escape, a process by which tumor cells evade immune surveillance, remains a challenge for cancer therapy. Tumor cells produce extracellular vesicles (EVs) that participate in immune escape by transferring bioactive molecules between cells. EVs refer to heterogeneous vesicles that participate in intercellular communication. EVs from tumor cells usually carry tumor antigens and have been considered a source of tumor antigens to induce anti-tumor immunity. However, evidence also suggests that these EVs can accelerate immune escape by carrying heat shock proteins (HSPs), programmed death-ligand 1 (PD-L1), etc. to immune cells, suppressing function and exhausting the immune cells pool. EVs are progressively being evaluated for therapeutic implementation in cancer therapies. EVs-based immunotherapies involve inhibiting EVs generation, using natural EVs, and harnessing engineering EVs. All approaches are associated with advantages and disadvantages. The EVs heterogeneity and diverse physicochemical properties are the main challenges to their clinical applications.

SHORT CONCLUSION

Although EVs are criminal; they can be useful for overcoming immune escape. This review discusses the latest knowledge on EVs population and sheds light on the function of tumor-derived EVs in immune escape. It also describes EVs-based immunotherapies with a focus on engineered EVs, followed by challenges that hinder the clinical translation of EVs that are essential to be addressed in future investigations. Video Abstract.

Size matters: Functional differences of small extracellular vesicle subpopulations in cardiac repair responses

Cardiac progenitor cell (CPC)-derived small extracellular vesicles (sEVs) exhibit great potential to stimulate cardiac repair. However, the multifaceted nature of sEV heterogeneity presents a challenge in understanding the distinct mechanisms underlying their regenerative abilities. Here, a dual-step multimodal flowthrough and size-exclusion chromatography method was applied to isolate and separate CPC-derived sEV subpopulations to study the functional differences related to cardiac repair responses. Three distinct sEV subpopulations were identified with unique protein profiles. Functional cell assays for cardiac repair-related processes demonstrated that the middle-sized and smallest-sized sEV subpopulations exhibited the highest pro-angiogenic and anti-fibrotic activities. Proteasome activity was uniquely seen in the smallest-sized subpopulation. The largest-sized subpopulation showed no effect in any of the functional assays. This research uncovers the existence of sEV subpopulations, each characterized by a distinct composition and biological function. Enhancing our understanding of sEV heterogeneity will provide valuable insights into sEV mechanisms of action, ultimately accelerating the translation of sEV therapeutics.

Unraveling the Multifaceted Roles of Extracellular Vesicles: Insights into Biology, Pharmacology, and Pharmaceutical Applications for Drug Delivery

Extracellular vesicles (EVs) are nanoparticles released from various cell types that have emerged as powerful new therapeutic option for a variety of diseases. EVs are involved in the transmission of biological signals between cells and in the regulation of a variety of biological processes, highlighting them as potential novel targets/platforms for therapeutics intervention and/or delivery. Therefore, it is necessary to investigate new aspects of EVs' biogenesis, biodistribution, metabolism, and excretion as well as safety/compatibility of both unmodified and engineered EVs upon administration in different pharmaceutical dosage forms and delivery systems. In this review, we summarize the current knowledge of essential physiological and pathological roles of EVs in different organs and organ systems. We provide an overview regarding application of EVs as therapeutic targets, therapeutics, and drug delivery platforms. We also explore various approaches implemented over the years to improve the dosage of specific EV products for different administration routes.

Hypothermia combined with extracellular vesicles from clonally expanded immortalized mesenchymal stromal cells improves neurodevelopmental impairment in neonatal hypoxic-ischemic brain injury

BACKGROUND

Neonatal encephalopathy following hypoxia-ischemia (HI) is a leading cause of childhood death and morbidity. Hypothermia (HT), the only available but obligatory therapy is limited due to a short therapeutic window and limited efficacy. An adjuvant therapy overcoming limitations of HT is still missing. Mesenchymal stromal cell (MSC)-derived extracellular vesicles (EVs) have shown promising therapeutic effects in various brain injury models. Challenges associated with MSCs' heterogeneity and senescence can be mitigated by the use of EVs from clonally expanded immortalized MSCs (ciMSCs). In the present study, we hypothesized that intranasal ciMSC-EV delivery overcomes limitations of HT.

METHODS

Nine-day-old C57BL/6 mice were exposed to HI by occlusion of the right common carotid artery followed by 1 h hypoxia (10% oxygen). HT was initiated immediately after insult for 4 h. Control animals were kept at physiological body core temperatures. ciMSC-EVs or vehicle were administered intranasally 1, 3 and 5 days post HI/HT. Neuronal cell loss, inflammatory and regenerative responses were assessed via immunohistochemistry, western blot and real-time PCR 7 days after insult. Long-term neurodevelopmental outcome was evaluated by analyses of cognitive function, activity and anxiety-related behavior 5 weeks after HI/HT.

RESULTS

In contrast to HT monotherapy, the additional intranasal therapy with ciMSC-EVs prevented HI-induced cognitive deficits, hyperactivity and alterations of anxiety-related behavior at adolescence. This was preceded by reduction of striatal neuronal loss, decreased endothelial, microglia and astrocyte activation; reduced expression of pro-inflammatory and increased expression of anti-inflammatory cytokines. Furthermore, the combination of HT with intranasal ciMSC-EV delivery promoted regenerative and neurodevelopmental processes, including endothelial proliferation, neurotrophic growth factor expression and oligodendrocyte maturation, which were not altered by HT monotherapy.

CONCLUSION

Intranasal delivery of ciMSC-EVs represents a novel adjunct therapy, overcoming limitations of acute HT thereby offering new possibilities for improving long-term outcomes in neonates with HI-induced brain injury.

Dual impacts of mesenchymal stem cell-derived exosomes on cancer cells: unravelling complex interactions

Mesenchymal stem cells (MSCs) are multipotent, self-renewing stromal cells found in a variety of adult tissues. MSCs possess a remarkable ability to migrate towards tumor sites, known as homing. This homing process is mediated by various factors, including chemokines, growth factors, and extracellular matrix components present in the tumor microenvironment. MSCs release extracellular vesicles known as exosomes (MSC-Exos), which have been suggested to serve a key role in mediating a wide variety of MSC activities. Through cell-cell communication, MSC-Exos have been shown to alter recipient cell phenotype or function and play as a novel cell-free alternative for MSC-based cell therapy. However, MSC recruitment to tumors allows for their interaction with cancer cells and subsequent regulation of tumor behavior. MSC-Exos act as tumor niche modulators via transferring exosomal contents, such as specific proteins or genetic materials, to the nearby cancer cells, leading to either promotion or suppression of tumorigenesis, angiogenesis, and metastasis, depending on the specific microenvironmental cues and recipient cell characteristics. Consequently, there is still a debate about the precise relationship between tumor cells and MSC-Exos, and it is unclear how MSC-Exos impacts tumor cells. Although the dysregulation of miRNAs is caused by the progression of cancer, they also play a direct role in either promoting or inhibiting tumor growth as they act as either oncogenes or tumor suppressors. The utilization of MSC-Exos may prove to be an effective method for restoring miRNA as a means of treating cancer. This review aimed to present the existing understanding of the impact that MSC-Exos could have on cancer. To begin with, we presented a brief explanation of exosomes, MSCs, and MSC-Exos. Following this, we delved into the impact of MSC-Exos on cancer growth, EMT, metastasis, angiogenesis, resistance to chemotherapy and radiotherapy, and modulation of the immune system. Opposing effects of mesenchymal stem cells-derived exosomes on cancer cells.

Engineered exosomes: A promising strategy for tendon-bone healing

BACKGROUND

Due to the spatiotemporal complexity of the composition, structure, and cell population of the tendon-bone interface (TBI), it is difficult to achieve true healing. Recent research is increasingly focusing on engineered exosomes, which are a promising strategy for TBI regeneration.

AIM OF REVIEW

This review discusses the physiological and pathological characteristics of TBI and the application and limitations of natural exosomes in the field of tendon-bone healing. The definition, loading strategies, and spatiotemporal properties of engineered exosomes were elaborated. We also summarize the application and future research directions of engineered exosomes in the field of tendon-bone healing.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Engineered exosomes can spatially deliver cargo to targeted sites and temporally realize the sustained release of therapeutic molecules in TBI. This review expounds on the multidifferentiation of engineered exosomes for tendon-bone healing, which effectively improves the biological and biomechanical properties of TBI. Engineered exosomes could be a promising strategy for tendon-bone healing.

Stem Cell-Derived Extracellular Vesicles for Cancer Therapy and Tissue Engineering Applications

Recently, stem cells and their secretomes have attracted great attention in biomedical applications, particularly extracellular vesicles (EVs). EVs are secretomes of cells for cell-to-cell communication. They play a role as intercellular messengers as they carry proteins, nucleic acids, lipids, and therapeutic agents. They have also been utilized as drug-delivery vehicles due to their biocompatibility, low immunogenicity, stability, targetability, and engineerable properties. The therapeutic potential of EVs can be further enhanced by surface engineering and modification using functional molecules such as aptamers, peptides, and antibodies. As a consequence, EVs hold great promise as effective delivery vehicles for enhancing treatment efficacy while avoiding side effects. Among various cell types that secrete EVs, stem cells are ideal sources of EVs because stem cells have unique properties such as self-renewal and regenerative potential for transplantation into damaged tissues that can facilitate their regeneration. However, challenges such as immune rejection and ethical considerations remain significant hurdles. Stem cell-derived EVs have been extensively explored as a cell-free approach that bypasses many challenges associated with cell-based therapy in cancer therapy and tissue regeneration. In this review, we summarize and discuss the current knowledge of various types of stem cells as a source of EVs, their engineering, and applications of EVs, focusing on cancer therapy and tissue engineering.

Hypoxic regulation of extracellular vesicles: Implications for cancer therapy

Extracellular vesicles (EVs) play a pivotal role in intercellular communication and have been implicated in cancer progression. Hypoxia, a pervasive hallmark of cancer, is known to regulate EV biogenesis and function. Hypoxic EVs contain a specific set of proteins, nucleic acids, lipids, and metabolites, capable of reprogramming the biology and fate of recipient cells. Enhancing the intrinsic therapeutic efficacy of EVs can be achieved by strategically modifying their structure and contents. Moreover, the use of EVs as drug delivery vehicles holds great promise for cancer treatment. However, various hurdles must be overcome to enable their clinical application as cancer therapeutics. In this review, we aim to discuss the current knowledge on the hypoxic regulation of EVs. Additionally, we will describe the underlying mechanisms by which EVs contribute to cancer progression in hypoxia and outline the progress and limitations of hypoxia-related EV therapeutics for cancer.

Neural stem cell-derived extracellular vesicles: The light of central nervous system diseases

Central nervous system (CNS) diseases are the leading cause of death worldwide. By performing compensatory functions and improving the inflammatory microenvironment, the transplantation of neural stem cells (NSCs) can promote functional recovery from brain injury, aging, brain tumours, and other diseases. However, the ability of NSCs to differentiate into neurons is limited, and they are associated with a risk of tumourigenicity. NSC-derived extracellular vesicles (NSC-EVs) can modulate the local microenvironment of the nervous system as well as distant neuronal functions. Thus, cell-free therapy may be a novel remedy for CNS disorders. This article reviews the characteristics, contents, and mechanisms of action of NSC-EVs as well as their roles and application prospects in various CNS diseases.