Characterization and Therapeutic Uses of Exosomes: A New Potential Tool in Orthopedics

Liquid biopsy for early cancer detection: technological revolutions and clinical dilemma

INTRODUCTION

Liquid biopsy is an innovative advancement in oncology, offering a noninvasive method for early cancer detection and monitoring by analyzing circulating tumor cells, DNA, RNA, and other biomarkers in bodily fluids. This technique has the potential to revolutionize precision oncology by providing real-time analysis of tumor dynamics, enabling early detection, monitoring treatment responses, and tailoring personalized therapies based on the molecular profiles of individual patients.

AREAS COVERED

In this review, the authors discuss current methodologies, technological challenges, and clinical applications of liquid biopsy. This includes advancements in detecting minimal residual disease, tracking tumor evolution, and combining liquid biopsy with other diagnostic modalities for precision oncology. Key areas explored are the sensitivity, specificity, and integration of multi-omics, AI, ML, and LLM technologies.

EXPERT OPINION

Liquid biopsy holds great potential to revolutionize cancer care through early detection and personalized treatment strategies. However, its success depends on overcoming technological and clinical hurdles, such as ensuring high sensitivity and specificity, interpreting results amidst tumor heterogeneity, and making tests accessible and affordable. Continued innovation and collaboration are crucial to fully realize the potential of liquid biopsy in improving early cancer detection, treatment, and monitoring.

Clinical Applications of Exosomes: A Critical Review

Exosomes, small membrane-bound vesicles secreted by cells, have gained significant attention for their therapeutic potential. Measuring 30-100 nm in diameter and derived from various cell types, exosomes play a crucial role in intercellular communication by transferring proteins, lipids, and RNA between cells. This review analyzes existing literature on the clinical applications of exosomes. We conducted a comprehensive search of peer-reviewed articles and clinical trial data to evaluate the benefits, limitations, and challenges of exosome-based therapies. Key areas of focus included regenerative medicine, cancer therapy, gene therapy, and diagnostic biomarkers. This review highlights the vast clinical applications of exosomes. In regenerative medicine, exosomes facilitate tissue repair and regeneration. In cancer therapy, exosomes can deliver therapeutic agents directly to tumor cells. In gene therapy, exosomes serve as vectors for gene delivery. As diagnostic biomarkers, they are useful in diagnosing various diseases. Challenges such as the isolation, purification, and characterization of exosomes were identified. Current clinical trials demonstrate the potential of exosome-based therapies, though they also reveal significant hurdles. Regulatory issues, including the need for standardization and validation of exosome products, are critical for advancing these therapies. While significant progress has been made in understanding exosome biology, further research is essential to fully unlock their clinical potential. Addressing challenges in isolation, purification, and regulatory standardization is crucial for their successful application in clinical practice. This review provides a concise overview of the clinical applications of exosomes, emphasizing both their therapeutic promise and the obstacles that need to be overcome.

Therapeutic potential of mesenchymal stem cell-derived exosomes in skeletal diseases

Skeletal diseases impose a considerable burden on society. The clinical and tissue-engineering therapies applied to alleviate such diseases frequently result in complications and are inadequately effective. Research has shifted from conventional therapies based on mesenchymal stem cells (MSCs) to exosomes derived from MSCs. Exosomes are natural nanocarriers of endogenous DNA, RNA, proteins, and lipids and have a low immune clearance rate and good barrier penetration and allow targeted delivery of therapeutics. MSC-derived exosomes (MSC-exosomes) have the characteristics of both MSCs and exosomes, and so they can have both immunosuppressive and tissue-regenerative effects. Despite advances in our knowledge of MSC-exosomes, their regulatory mechanisms and functionalities are unclear. Here we review the therapeutic potential of MSC-exosomes for skeletal diseases.

The Effect of Local Purified Exosome Product, Stem Cells, and Tacrolimus on Neurite Extension

PURPOSE

The combination of cellular and noncellular treatments has been postulated to improve nerve regeneration through a processed nerve allograft. This study aimed to evaluate the isolated effect of treatment with purified exosome product (PEP), mesenchymal stem cells (MSCs), and tacrolimus (FK506) alone and in combination when applied in decellularized allografts.

METHODS

A three-dimensional in vitro-compartmented cell culture system was used to evaluate the length of regenerating neurites from the neonatal dorsal root ganglion into the adjacent peripheral nerve graft. Decellularized nerve allografts were treated with undifferentiated MSCs, 5% PEP, 100 ng/mL FK506, PEP and FK506 combined, or MSCs and FK506 combined (N = 9/group) and compared with untreated nerve autografts (positive control) and nerve allografts (negative control). Neurite extension was measured to quantify nerve regeneration after 48 hours, and stem cell viability was evaluated.

RESULTS

Stem cell viability was confirmed in all MSC-treated nerve grafts. Treatments with PEP, PEP + FK506, and MSCs + FK506 combined were found to be superior to untreated allografts and not significantly different from autografts. Combined PEP and FK506 treatment resulted in the greatest neurite extension. Treatment with FK506 and MSCs was significantly superior to MSC alone. The combined treatment groups were not found to be statistically different.

CONCLUSIONS

Although all treatments improved neurite outgrowth, treatments with PEP, PEP + FK506, and MSCs + FK506 combined had superior neurite growth compared with untreated allografts and were not found to be significantly different from autografts, the current gold standard.

CLINICAL RELEVANCE

Purified exosome product, a cell-free exosome product, is a promising adjunct to enhance nerve allograft regeneration, with possible future avenues for clinical translation.

The Role of Exosomes in Upper-Extremity Tissue Regeneration

Exosomes are cell-free membrane vesicles secreted by a wide variety of cells as secretomes into the extracellular matrix. Alongside facilitating intercellular communication, exosomes carry various bioactive molecules consisting of nucleic acids, proteins, and lipids. Exosome applications have increased in popularity by overcoming the disadvantages of mesenchymal stem cell therapies. Despite this, a better understanding of the underlying mechanisms of action of exosomes is necessary prior to clinical application in upper-extremity tissue regeneration. The purpose of this review is to introduce the concept of exosomes and their possible applications in upper-extremity tissue regeneration, detail the shortcomings of current exosome research, and explore their potential clinical application in the upper extremity.

Adipose Tissue-Derived Extracellular Vesicles: A Promising Biomarker and Therapeutic Strategy for Metabolic Disorders

Adipose tissue plays an important role in systemic energy metabolism, and its dysfunction can lead to severe metabolic disorders. Various cells in adipose tissue communicate with each other to maintain metabolic homeostasis. Extracellular vesicles (EVs) are recognized as novel medium for remote intercellular communication by transferring various bioactive molecules from parental cells to distant target cells. Increasing evidence suggests that the endocrine functions of adipose tissue and even the metabolic homeostasis are largely affected by different cell-derived EVs, such as insulin signaling, lipolysis, and metabolically triggered inflammation regulations. Here, we provide an overview focused on the role of EVs released by different cell types of adipose tissue in metabolic diseases and their possible molecular mechanisms and highlight the potential applications of EVs as biomarkers and therapeutic targets. Moreover, the current EVs-based therapeutic strategies have also been discussed. This trial is registered with NCT05475418.

Dose-response analysis after administration of a human platelet-derived exosome product on neurite outgrowth in vitro

Modulating the nerve's local microenvironment using exosomes is proposed to enhance nerve regeneration. This study aimed to determine the optimal dose of purified exosome product (PEP) required to exert maximal neurite extension. An in vitro dorsal root ganglion (DRG) neurite outgrowth assay was used to evaluate the effect of treatment with (i) 5% PEP, (ii) 10% PEP, (iii) 15% PEP, or (iv) 20% PEP on neurite extension (N = 9/group), compared to untreated controls. After 72 h, neurite extension was measured to quantify nerve regeneration. Live cell imaging was used to visualize neurite outgrowth during incubation. Treatment with 5% PEP resulted in the longest neurite extension and was superior to the untreated DRG (p = 0.003). Treatment with 10% PEP, 15% PEP, and 20% PEP was found to be comparable to controls (p = 0.12, p = 0.06, and p = 0.41, respectively) and each other. Live cell imaging suggested that PEP migrated towards the DRG neural regeneration site, compared to the persistent homogenous distribution of PEP in culture media alone. 5% PEP was found to be the optimal concentration for nerve regeneration based on this in vitro dose-response analysis.

Exosomes and ultrasound: The future of theranostic applications

Biomaterials and pertaining formulations have been very successful in various diagnostic and therapeutic applications because of its ability to overcome pharmacological limitations. Some of them have gained significant focus in the recent decade for their theranostic properties. Exosomes can be grouped as biomaterials, since they consist of various biological micro/macromolecules and possess all the properties of a stable biomaterial with size in nano range. Significant research has gone into isolation and exploitation of exosomes as potential theranostic agent. However, the limitations in terms of yield, efficacy, and target specificity are continuously being addressed. On the other hand, several nano/microformulations are responsive to physical or chemical alterations and were successfully stimulated by tweaking the physical characteristics of the surrounding environment they are in. Some of them are termed as photodynamic, sonodynamic or thermodynamic therapeutic systems. In this regard, ultrasound and acoustic systems were extensively studied for its ability towards altering the properties of the systems to which they were applied on. In this review, we have detailed about the diagnostic and therapeutic applications of exosomes and ultrasound separately, consisting of their conventional applications, drawbacks, and developments for addressing the challenges. The information were categorized into various sections that provide complete overview of the isolation strategies and theranostic applications of exosomes in various diseases. Then the ultrasound-based disease diagnosis and therapy were elaborated, with special interest towards the use of ultrasound in enhancing the efficacy of nanomedicines and nanodrug delivery systems, Finally, we discussed about the ability of ultrasound in enhancing the diagnostic and therapeutic properties of exosomes, which could be the future of theranostics.

Future perspective of stem cell-derived exosomes: Cell-free therapeutic strategies for retinal degeneration

With continued expansion of the aged population, the number of patients with retinal degeneration, which is a leading cause of vision loss worldwide, is growing. Stem cell therapies offer hope for regeneration and repair of damaged retinal tissue. Recent reports have highlighted stem cell-derived paracrine mediators, such as exosomes, which appear to exert a therapeutic benefit similar to their cell of origin and do not carry the risk of cell transplantation. One speculated role is that exosomes likely mediate intercellular communication and material exchange. This review depicts the molecular mechanisms underlying exosome-based therapy, especially in retina degeneration diseases. In the future, the use of stem cell-derived exosomes could be considered a novel and cell-free therapeutic strategy in regenerative medicine.

Exosomes derived from cyclic mechanical stretch-exposed bone marrow mesenchymal stem cells inhibit RANKL-induced osteoclastogenesis through the NF-κB signaling pathway

Background

Skeletal unloading usually induces severe disuse osteoporosis (DOP), which often occurs in patients subjected to prolonged immobility or in spaceflight astronauts. Increasing evidence suggests that exosomes are important mediators in maintaining the balance between bone formation and resorption. We hypothesized that exosomes play an important role in the maintenance of bone homeostasis through intercellular communication between bone marrow mesenchymal stem cells (BMSCs) and osteoclasts under mechanical loading.

Methods

Cells were divided into cyclic mechanical stretch (CMS)-treated BMSCs and normal static-cultured BMSCs, and exosomes were extracted by ultracentrifugation. After incubation with CMS-treated BMSC-derived exosomes (CMS_Exos) or static-cultured BMSC-derived exosomes (static_Exos), the apoptosis rates of bone marrow macrophages (BMMs) were determined by flow cytometry, and cell viability was detected with a Cell Counting Kit-8 (CCK-8) assay. Osteoclast differentiation was determined with an in vitro osteoclastogenesis assay. Signaling pathway activation was evaluated by western blotting and immunofluorescence staining. Hindlimb unloading (HU)-induced DOP mouse models were prepared to evaluate the function of exosomes in DOP.

Results

Both CMS_Exos and static_Exos could be internalized by BMMs, and CMS_Exos did not affect BMM viability or increase apoptosis. The CMS_Exos effectively suppressed receptor activator of nuclear factor kappa-B ligand (RANKL)-mediated osteoclastogenesis and F-actin ring formation. Further molecular investigation demonstrated that CMS_Exos impaired osteoclast differentiation via inhibition of the RANKL-induced nuclear factor kappa-B (NF-κB) signaling pathway. Both CMS_Exos and static_Exos partly rescued the osteoporosis caused by mechanical unloading; however, the CMS_Exo group showed more obvious rescue. Treatment with CMS_Exos significantly decreased the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts. Exosomes derived from CMS-treated BMSCs strongly inhibited osteoclast differentiation by attenuating the NF-κB signaling pathway in vitro and rescued osteoporosis caused by mechanical unloading in an HU mouse model in vivo.

Conclusions

In this research, we demonstrated that Exosomes derived from CMS-treated BMSCs inhibited osteoclastogenesis by attenuating NF-κB signaling pathway activity in vitro and ameliorated bone loss caused by mechanical unloading in an HU mouse model, providing new insights into intercellular communication between osteoblasts and osteoclasts under mechanical loading.

A Review of the Functions of Matrix Vesicles in Periodontal Tissues

Periodontal tissues consist of cementum, periodontal ligaments, and alveolar bone, which provide indispensable support for physiological activities involving mastication, swallowing, and pronunciation. The formation of periodontal tissues requires a complex process, during which a close relationship with biomineralization is noticeable. Alveolar bone and cementum are physically hard, both of which are generated from biomineralization and possess the exact mechanical properties resembling other hard tissues. However, when periodontitis, congenital abnormalities, periapical diseases, and other pathological conditions affect the organism, the most common symptom, alveolar bone defect, is always unavoidable, which results in difficulties for current clinical treatment. Thus, exploring effective therapies to improve the prognosis is important. Matrix vesicles (MVs), a special subtype of extracellular vesicles related to histogenesis, are widely produced by the stem cells of developing hard tissues. With the assistance of the enzymes and transporters contained within them, MVs can construct the extracellular matrix and an adequate microenvironment, thus promoting biomineralization and periodontal development. Presently, MVs can be effectively extracted and delivered by scaffolds and generate hard tissues in vitro and in vivo, which are expected to be translated into therapies for alveolar bone defects. In this review, we generalize recent research progress on MV morphology, molecular composition, biological mechanism, and, in particular, the biological functions in periodontal development. In addition to the above unique roles of MVs, we further describe the available MV-related biotechnologies and achievements that make them promising for coping with existing problems and improving the treatment of alveolar bone defects.

Emerging Roles of Exosomes in T1DM

Type 1 diabetes mellitus (T1DM) is a complex autoimmune disorder that mainly affects children and adolescents. The elevated blood glucose level of patients with T1DM results from absolute insulin deficiency and leads to hyperglycemia and the development of life-threatening diabetic complications. Although great efforts have been made to elucidate the pathogenesis of this disease, the precise underlying mechanisms are still obscure. Emerging evidence indicates that small extracellular vesicles, namely, exosomes, take part in intercellular communication and regulate interorgan crosstalk. More importantly, many findings suggest that exosomes and their cargo are associated with the development of T1DM. Therefore, a deeper understanding of exosomes is beneficial for further elucidating the pathogenic process of T1DM. Exosomes are promising biomarkers for evaluating the risk of developingty T1DM, monitoring the disease state and predicting related complications because their number and composition can reflect the status of their parent cells. Additionally, since exosomes are natural carriers of functional proteins, RNA and DNA, they can be used as therapeutic tools to deliver these molecules and drugs. In this review, we briefly introduce the current understanding of exosomes. Next, we focus on the relationship between exosomes and T1DM from three perspectives, i.e., the pathogenic role of exosomes in T1DM, exosomes as novel biomarkers of T1DM and exosomes as therapeutic tools for T1DM.

Progress in Microfluidics-Based Exosome Separation and Detection Technologies for Diagnostic Applications

Exosomes are secreted by most cell types and circulate in body fluids. Recent studies have revealed that exosomes play a significant role in intercellular communication and are closely associated with the pathogenesis of disease. Therefore, exosomes are considered promising biomarkers for disease diagnosis. However, exosomes are always mixed with other components of body fluids. Consequently, separation methods for exosomes that allow high-purity and high-throughput separation with a high recovery rate and detection techniques for exosomes that are rapid, highly sensitive, highly specific, and have a low detection limit are indispensable for diagnostic applications. For decades, many exosome separation and detection techniques have been developed to achieve the aforementioned goals. However, in most cases, these two techniques are performed separately, which increases operation complexity, time consumption, and cost. The emergence of microfluidics offers a promising way to integrate exosome separation and detection functions into a single chip. Herein, an overview of conventional and microfluidics-based techniques for exosome separation and detection is presented. Moreover, the advantages and drawbacks of these techniques are compared.