Aptamer-functionalized exosomes from bone marrow stromal cells target bone to promote bone regeneration

Surface-modified engineered exosomes attenuated cerebral ischemia/reperfusion injury by targeting the delivery of quercetin towards impaired neurons

BACKGROUND

The incidence of ischemic stroke in the context of vascular disease is high, and the expression of growth-associated protein-43 (GAP43) increases when neurons are damaged or stimulated, especially in a rat model of middle cerebral artery occlusion/reperfusion (MCAO/R).

EXPERIMENTAL

DESIGN: We bioengineered neuron-targeting exosomes (Exo) conjugated to a monoclonal antibody against GAP43 (mAb GAP43) to promote the targeted delivery of quercetin (Que) to ischemic neurons with high GAP43 expression and investigated the ability of Exo to treat cerebral ischemia by scavenging reactive oxygen species (ROS).

RESULTS

Our results suggested that Que loaded mAb GAP43 conjugated exosomes (Que/mAb GAP43-Exo) can specifically target damaged neurons through the interaction between Exo-delivered mAb GAP43 and GAP43 expressed in damaged neurons and improve survival of neurons by inhibiting ROS production through the activation of the Nrf2/HO-1 pathway. The brain infarct volume is smaller, and neurological recovery is more markedly improved following Que/mAb GAP43-Exo treatment than following free Que or Que-carrying exosome (Que-Exo) treatment in a rat induced by MCAO/R.

CONCLUSIONS

Que/mAb GAP43-Exo may serve a promising dual targeting and therapeutic drug delivery system for alleviating cerebral ischemia/reperfusion injury.

Mesenchymal stromal cell-derived extracellular vesicles for bone regeneration therapy

Purpose

To analyze preclinical bone regeneration studies employing mesenchymal stromal cell (MSC)- derived extracellular vesicles (EVs) and highlight any commonalities in EV biomarker expression, miRNA cargo(s) or pathway activation that will aid in understanding the underlying therapeutic mechanisms.

Methods

Articles employing EVs derived from either MSCs or MSC-like osteogenic stromal cells in preclinical bone regeneration studies are included in this review.

Results

EVs derived from a variety of MSC types were able to successfully induce bone formation in preclinical models. Many studies failed to perform in-depth EV characterization. The studies with detailed EV characterization data report very different miRNA cargos, even in EVs isolated from the same species and cell types. Few preclinical studies have analyzed the underlying mechanisms of MSC-EV therapeutic action.

Conclusion

There is a critical need for mechanistic preclinical studies with thorough EV characterization to determine the best therapeutic MSC-EV source for bone regeneration therapies. Issues including controlled EV delivery, large scale production, and proper storage also need to be addressed before EV-based bone regeneration therapies can be translated for clinical bone repair.

•

EVs from different MSC sources successfully regenerate bone in preclinical models.

•

Studies were reviewed to find commonalities in EV cargo(s)/pathways activated in MSC-EV-based bone regeneration therapies.

•

Issues that need to be overcome to enable clinical translation of EV-based therapies were addressed.

Targeted inhibition of SIRT6 via engineered exosomes impairs tumorigenesis and metastasis in prostate cancer

The treatment for metastatic castration-resistant prostate cancer patients remains a great challenge in the clinic and continuously demands discoveries of new targets and therapies. Here, we assess the function and therapeutic value of SIRT6 in metastatic castration-resistant prostate cancer. Methods: The expression of SIRT6 was examined in prostate cancer tissue microarray by immunohistochemistry staining. The functions of SIRT6 and underlying mechanisms were elucidated by in vitro and in vivo experiments. We also developed an efficient method to silence SIRT6 by aptamer-modified exosomes carrying small interfering RNA and tested the therapeutic effect in the xenograft mice models. Results: SIRT6 expression is positively correlated with prostate cancer progression. Loss of SIRT6 significantly suppressed proliferation and metastasis of prostate cancer cell lines both in vitro and in vivo. SIRT6-driven prostate cancer displays activation of multiple cancer-related signaling pathways, especially the Notch pathway. Silencing SIRT6 by siRNA delivered through engineered exosomes inhibited tumor growth and metastasis. Conclusions: SIRT6 is identified as a driver and therapeutic target for metastatic prostate cancer in our findings, and inhibition of SIRT6 by engineered exosomes can serve as a promising therapeutic tool for clinical application.

Extracellular Vesicles from Akkermansia muciniphila Elicit Antitumor Immunity Against Prostate Cancer via Modulation of CD8+ T Cells and Macrophages

PURPOSE

Prostate cancer (PCa) is one of the most common malignancies in males. Despite the success of immunotherapy in many malignant cancers, strategies are still needed to improve therapeutic efficacy in PCa. This study aimed to investigate the effects of Akkermansia muciniphila-derived extracellular vesicles (Akk-EVs) on PCa and elucidate the underlying immune-related mechanism.

METHODS

Akk-EVs were isolated by ultracentrifugation and intravenously injected to treat syngeneic PCa-bearing immune-competent mice. Immunophenotypic changes in immune cells, such as cytotoxic T lymphocytes and macrophages, were measured via flow cytometry analysis. Histological examination was used to detect morphological changes in major organs after Akk-EVs treatments. In vitro, flow cytometry was performed to confirm the effects of Akk-EVs on the activation of CD8+ T cells. Quantitative PCR and immunofluorescence staining were carried out to test the impact of Akk-EVs on macrophage polarization. Cell counting kit-8 (CCK-8) analysis, colony formation assays, and scratch wound healing assays were conducted to assess the effects of Akk-EVs-treated macrophages on the proliferation and invasion of PCa cells. CCK-8 assays also confirmed the impact of Akk-EVs on the viability of normal cells.

RESULTS

Intravenous injection of Akk-EVs in immune-competent mice reduced the tumor burden of PCa without inducing obvious toxicity in normal tissues. This treatment elevated the proportion of granzyme B-positive (GZMB+) and interferon γ-positive (IFN-γ+) lymphocytes in CD8+ T cells and caused macrophage recruitment, with increased tumor-killing M1 macrophages and decreased immunosuppressive M2 macrophages. In vitro, Akk-EVs increased the number of GZMB+CD8+ and IFN-γ+CD8+ T cells and M1-like macrophages. In addition, conditioned medium from Akk-EVs-treated macrophages suppressed the proliferation and invasion of prostate cells. Furthermore, the effective dose of Akk-EVs was well-tolerated in normal cells.

CONCLUSION

Our study revealed the promising prospects of Akk-EVs as an efficient and biocompatible immunotherapeutic agent for PCa treatment.

Promising diagnostic and therapeutic circRNAs for skeletal and chondral disorders

Circular RNAs (circRNAs) belong to a highly conserved subtype of non-coding RNAs, produced by the back-splicing of specific regions of pre-mRNA. CircRNAs have wide-ranging effects on eukaryotic physiology and pathology by acting as transcription regulators, miRNA sponges, protein sponges, and templates for translation. Skeletal and chondral disorders are the leading causes of pain and disability, especially for elders, affecting hundreds of millions of people worldwide. Plenty of evidence have shown that circRNAs are dysregulated and play vital roles in the occurrence and progression of skeletal and chondral disorders. Herein, we systematically summarize the emerging roles and underlying molecular mechanisms of hub circRNAs in the pathogenesis of several representative skeletal and chondral disorders. Our findings may provide further insight into the mechanistic details of the role of circRNA in bone or cartilage metabolism, and highlight the promising application of circRNAs in serving as potential diagnostic or therapeutic targets for the prevention and treatment of skeletal and chondral disorders.

Identification of the canonical and noncanonical role of miR-143/145 in estrogen-deficient bone loss

Rationale: Postmenopausal-induced bone loss is mainly caused by declining core transcription factors (TFs) of bone mesenchymal stem cells (BMSCs), but little is known about how miRNAs regulate chromatin structure remodeling of TFs gene to maintain BMSCs function in bone homeostasis. Methods: We examined the serum, salivary and bone samples from Pre- and Post-menopause women by paired analysis and confirmed canonical ceRNA role of MIR143HG and miR-143/145 complexes in cytoplasm and noncanonical role for SOX2 transcription in nucleus (FISH, qRT-PCR, immunostaining, Luciferase assays and ChIP). Moreover, we took advantage of transgenic mice under OVX-induced osteoporosis, studying the in vitro and in vivo effect of miR-143/145 deletion on BMSCs function and bone homeostasis. Last, using miRNA antagonism, antagomiR-143/145 were delivered into bone marrow to treat estrogen-deficient bone loss. Results: Here, we identified miR-143/145 as potential diagnostic candidates for postmenopausal osteoporosis, and miR-143/145 overexpression impaired BMSCs self-renewing and differentiation function. Mechanistically, we confirmed that cytoplasmic miR-143/145 and LncRNA MIR143HG, that controlled by ERβ, cooperatively regulated pluripotency genes translation via canonical ceRNA pathway, and MIR143HG cooperates with miR‑143 to nuclear translocation for co-activation of SOX2 transcription via opening promoter chromatin. Meanwhile, miR‑143/145 were shuttled into osteoclasts in extracellular vesicles and triggered osteoclastic activity by targeting Cd226 and Srgap2. Furthermore, miR-143/145-/- mice or using chemically‑modified antagomiR-143/145 significantly alleviated estrogen-deficient osteoporosis. Conclusions: Our findings reveal a canonical and noncanonical role of miR-143/145 in controlling BMSCs pluripotency and unfold their dual effect on bone formation and bone resorption, suggesting miR-143/145 as promising therapeutic targets for treating estrogen-deficient bone loss.

MicroRNA function in craniofacial bone formation, regeneration and repair

Bone formation in the craniofacial complex is regulated by cranial neural crest (CNC) and mesoderm-derived cells. Different elements of the developing skull, face, mandible, maxilla (jaws) and nasal bones are regulated by an array of transcription factors, signaling molecules and microRNAs (miRs). miRs are molecular modulators of these factors and act to restrict their expression in a temporal-spatial mechanism. miRs control the different genetic pathways that form the craniofacial complex. By understanding how miRs function in vivo during development they can be adapted to regenerate and repair craniofacial genetic anomalies as well as bone diseases and defects due to traumatic injuries. This review will highlight some of the new miR technologies and functions that form new bone or inhibit bone regeneration.

Resveratrol benefits the lineage commitment of bone marrow mesenchymal stem cells into osteoblasts via miR-320c by targeting Runx2

Bone marrow mesenchymal stem cells (BMSCs) are a potential source of osteoblasts and have been widely used in clinical therapies due to their pluripotency. Recent publications have found that resveratrol (RSVL) played a crucial role in the proliferation and differentiation of BMSCs; however, the underlying molecular mechanism of RSVL-induced BMSCs osteogenic differentiation needs to be fully elucidated. The objective of this study was to explore functions of miRNAs in the RSVL-treated BMSCs and its effects on the differentiation potentials of BMSCs. The findings demonstrated that RSVL enhanced the osteogenesis and suppressed the adipogenesis of BMSCs in a dose-dependent manner. Besides, a novel regulatory axis containing miR-320c, and its target Runx2 was found during the differentiation process of BMSCs under RSVL treatment. Increase of miR-320c reduced the osteogenic potential of BMSCs, while knockdown of miR-320c played a positive role in the osteogenesis of BMSCs. In contrast, overexpression of miR-320c accelerated the adipogenic differentiation, while knockdown of miR-320c restrained the adipogenic differentiation of BMSCs. The results confirmed that Runx2 might be the direct target of miR-320c in RSVL-promoted osteogenic differentiation of BMSCs. This study revealed that RSVL might be used for the treatment of bone loss related diseases and miR-320c could be regarded as a novel and potential target to regulate the biological functions of BMSCs.

FBS-Derived Exosomes as a Natural Nano-Scale Carrier for Icariin Promote Osteoblast Proliferation

Icariin is a class IV drug of low solubility, permeability, and poor bioavailability. Synthetic nanomaterials have developed rapidly. However, some literatures point out that synthetic nanomaterials such as liposomes, aptamers, metal nanoparticles, and nanogels have high toxicity and are affected by the reticuloendothelial system or mononuclear phagocyte system. It is known that exosomes could be used as an ideal clinical drug delivery vehicle to avoid the above-mentioned problems to a certain extent. Studies have shown that drugs can be loaded into exosomes by passive and active loading. We used Fetal bovine serum (FBS) exosomes to carry Icariin for the first time in this experiment, FBS exosomes-Icariin (FBS EXO-ICA) more effectively promoted the proliferation of osteoblasts and bone regeneration than Icariin alone. FBS EXO-ICA could become a new nano scale drug formulation for treating diseases associated with bone loss.

Tissue Regeneration Capacity of Extracellular Vesicles Isolated From Bone Marrow-Derived and Adipose-Derived Mesenchymal Stromal/Stem Cells

Mesenchymal stem cell (MSC)-based therapies have demonstrated tissue repair and regeneration capacity in various preclinical models. These therapeutic effects have recently been largely attributed to the paracrine effects of the MSC secretome, including proteins and extracellular vesicles (EVs). EVs are cell-secreted nano-sized vesicles with lipid bilayer membranes that facilitate cell–cell signaling. Treatments based on MSC-derived EVs are beginning to be explored as an alternative to MSC transplantation-based therapies. However, it remains to be determined which MSC source produces EVs with the greatest therapeutic potential. This review compares the tissue regeneration capacity of EVs isolated from the two most common clinical sources of adult MSCs, bone marrow and adipose tissue, with a particular focus on their angiogenic, osteogenic, and immunomodulatory potentials. Other important issues in the development of MSC-derived EV based therapies are also discussed.

miRNA-92a-3p regulates osteoblast differentiation in patients with concomitant limb fractures and TBI via IBSP/PI3K-AKT inhibition

Patients who sustain concomitant fractures and traumatic brain injury (TBI) are known to have significantly quicker fracture-healing rates than patients with isolated fractures. The mechanisms underlying this phenomenon have yet to be identified. In the present study, we found that the upregulation of microRNA-92a-3p (miRNA-92a-3p) induced by TBI correlated with a decrease in integrin binding sialoprotein (IBSP) expression in callus formation. In vitro, overexpressing miRNA-92a-3p inhibited IBSP expression and accelerated osteoblast differentiation, whereas silencing of miRNA-92a-3p inhibited osteoblast activity. A decrease in IBSP facilitated osteoblast differentiation via the Phosphatidylinositol 3-kinase/threonine kinase 1 (PI3K/AKT) signaling pathway. Through luciferase assays, we found evidence that IBSP is a miRNA-92a-3p target gene that negatively regulates osteoblast differentiation. Moreover, the present study confirmed that pre-injection of agomiR-92a-3p leads to increased bone formation. Collectively, these results indicate that miRNA-92a-3p overexpression may be a key factor underlying the improved fracture healing observed in TBI patients. Upregulation of miRNA-92a-3p may therefore be a promising therapeutic strategy for promoting fracture healing and preventing nonunion.

Bone Marrow Mesenchymal Stem Cells-Derived Exosomal MicroRNA-150-3p Promotes Osteoblast Proliferation and Differentiation in Osteoporosis

At present, much more studies have focused on the role of microRNAs in osteoporosis, but the more specific role of microRNA-150-3p (miR-150-3p) in osteoporosis still needs full exploration. We aim at investigating the role of miR-150-3p in osteoporosis and at exploring the related mechanisms. Bone marrow mesenchymal stem cells (BMSCs) were cultured, from which exosomes were isolated. Osteoporosis models were established by ovariectomy and injected with transfected BMSCs exosomes. Bone formation markers in serum, histopathological changes and miR-150-3p, runt-related transcription factor 2 (Runx2) and Osterix expression, and osteoblast apoptosis in femoral tissues were detected. Osteoblasts were isolated and co-cultured with the transfected BMSCs-derived exosomes. Osteoblast proliferation, cell differentiation, and apoptosis, along with miR-150-3p, Runx2, and Osterix expression in osteoblasts were detected. In vivo experiment demonstrated that miR-150-3p, Runx2, and Osterix expression was decreased whereas bone formation markers were decreased in osteoporosis. BMSCs exosomes attenuated osteoporosis, which was further improved by upregulated miR-150-3p in exosomes whereas it was impaired by downregulated miR-150-3p in exosomes. In vitro experiments declared decreased miR-150-3p, Runx2, and Osterix expression; suppressed proliferation; and encouraged apoptosis in osteoblasts in osteoporosis. BMSCs exosomes promoted osteoblast proliferation and differentiation and inhibited apoptosis, which was strengthened by raised exosomal miR-150-3p whereas it was disrupted by inhibited exosomal miR-150-3p. Our study elucidates that exosomal miR-150-3p promotes osteoblast proliferation and differentiation in osteoporosis and provides a new clue for the treatment of patients with osteoporosis.

Icariin Promotes the Osteogenesis of Bone Marrow Mesenchymal Stem Cells through Regulating Sclerostin and Activating the Wnt/β-Catenin Signaling Pathway

Osteoporosis (OP) is a metabolic disease characterized by decreased bone mass and increased risk of fragility fractures, which significantly reduces the quality of life. Stem cell-based therapies, especially using bone marrow mesenchymal stem cells (BMSCs), are a promising strategy for treating OP. Nevertheless, the survival and differentiation rates of the transplanted BMSCs are low, which limits their therapeutic efficiency. Icariin (ICA) is a traditional Chinese medicine formulation that is prescribed for tonifying the kidneys. It also promotes the proliferation and osteogenic differentiation of BMSCs, although the specific mechanism remains unclear. Based on our previous research, we hypothesized that ICA promotes bone formation via the sclerostin/Wnt/β-catenin signaling pathway. We isolated rat BMSCs and transfected them with sclerostin gene (SOST) overexpressing or knockdown constructs and assessed osteogenic induction in the presence or absence of ICA. Sclerostin significantly inhibited BMSC proliferation and osteogenic differentiation, whereas the presence of ICA not only increased the number of viable BMSCs but also enhanced ALP activity and formation of calcium nodules during osteogenic induction. In addition, the osteogenic genes including Runx2, β-catenin, and c-myc as well as antioxidant factors (Prdx1, Cata, and Nqo1) were downregulated by sclerostin and restored by ICA treatment. Mechanistically, ICA exerted these effects by activating the Wnt/β-catenin pathway. In conclusion, ICA can promote the proliferation and osteogenic differentiation of BMSCs in situ and therefore may enhance the therapeutic efficiency of BMSC transplantation in OP.

Extracellular vesicles in bone and periodontal regeneration: current and potential therapeutic applications

Oral mesenchymal stem cells (MSCs) and their secretomes are considered important factors in the field of medical tissue engineering and cell free biotherapy due to their ease of access, differentiation potential, and successful therapeutic outcomes. Extracellular vesicles (EVs) and the conditioned medium (CM) from MSCs are gaining more attraction as an alternative to cell-based therapies due to the less ethical issues involved, and their easier acquisition, preservation, long term storage, sterilization, and packaging. Bone and periodontal regenerative ability of EVs and CM have been the focus of some recent studies. In this review, we looked through currently available literature regarding MSCs' EVs or conditioned medium and their general characteristics, function, and regenerative potentials. We will also review the novel applications in regenerating bone and periodontal defects.

The Role of Mesenchymal Stromal Cells-Derived Small Extracellular Vesicles in Diabetes and Its Chronic Complications

Mesenchymal stromal cells (MSCs) are applied in regenerative medicine of several tissues and organs nowadays by virtue of their self-renewal capabilities, multiple differentiation capacity, potent immunomodulatory properties, and their ability to be favourably cultured and manipulated. With the continuous development of "cell-free therapy" research, MSC-derived small extracellular vesicles (MSC-sEVs) have increasingly become a research hotspot in the treatment of various diseases. Small extracellular vesicles (SEVs) are membrane vesicles with diameters of 30 to 150 nm that mediate signal transduction between adjacent or distal cells or organs by delivering non-coding RNA, protein, and DNA. The contents and effects of sEVs vary depending on the properties of the originating cell. In recent years, MSC-sEVs have been found to play an important role in the occurrence and development of diabetes mellitus as a new way of communication between cells. Diabetes mellitus is a common metabolic disease in clinic. Its complications of the heart, brain, kidney, eyes, and peripheral nerves are a serious threat to human health and has been a hot issue for clinicians. MSC-sEVs could be applied to repair or prevent damage from the complications of diabetes mellitus through anti-inflammatory effects, reduction of endoplasmic reticulum-related protein stress, polarization of M2 macrophages, and increasing autophagy. Therefore, we highly recommend that MSC-sEVs-based therapies to treat diabetes mellitus and its chronic complication be further explored. The analysis of the role and molecular mechanisms of MSC-sEVs in diabetes and its related complications will provide new idea and insights for the prevention and treatment of diabetes.

Clinical Application of Bone Marrow Mesenchymal Stem/Stromal Cells to Repair Skeletal Tissue

There has been an escalation in reports over the last decade examining the efficacy of bone marrow derived mesenchymal stem/stromal cells (BMSC) in bone tissue engineering and regenerative medicine-based applications. The multipotent differentiation potential, myelosupportive capacity, anti-inflammatory and immune-modulatory properties of BMSC underpins their versatile nature as therapeutic agents. This review addresses the current limitations and challenges of exogenous autologous and allogeneic BMSC based regenerative skeletal therapies in combination with bioactive molecules, cellular derivatives, genetic manipulation, biocompatible hydrogels, solid and composite scaffolds. The review highlights the current approaches and recent developments in utilizing endogenous BMSC activation or exogenous BMSC for the repair of long bone and vertebrae fractures due to osteoporosis or trauma. Current advances employing BMSC based therapies for bone regeneration of craniofacial defects is also discussed. Moreover, this review discusses the latest developments utilizing BMSC therapies in the preclinical and clinical settings, including the treatment of bone related diseases such as Osteogenesis Imperfecta.

BMSC-Derived Exosomal miR-29a Promotes Angiogenesis and Osteogenesis

Angiogenesis and osteogenesis are tightly coupled during bone modeling and remodeling processes. Here we reported that bone marrow mesenchymal stem cell (BMSC)-derived exosomal miR-29a promotes angiogenesis and osteogenesis in vitro and in vivo. BMSC-derived exosomes (BMSCs-Exos) can be taken up by human umbilical vein endothelial cells (HUVECs) and promote the proliferation, migration, and tube formation of HUVECs. MiRNA-29a level was high in BMSCs-Exos and can be transported into HUVECs to regulate angiogenesis. VASH1 was identified as a direct target of miR-29a, mediating the effects of BMSC-derived exosomal miR-29a on angiogenesis. More interestingly, miR29a-loaded exosomes from engineered BMSCs (miR-29a-loaded BMSCs-Exos) showed a robust ability of promoting angiogenesis and osteogenesis in vivo. Taken together, these findings suggest that BMSC-derived exosomal miR-29a regulates angiogenesis and osteogenesis, and miR-29a-loaded BMSCs-Exos may serve as a potential therapeutic target for osteoporosis.

Therapeutic Potential of Exosomes in Pulmonary Fibrosis

Pulmonary fibrosis is closely associated with the recruitment of fibroblasts from capillary vessels with damaged endothelial cells, the epithelial mesenchymal transition (EMT) of type II alveolar epithelial cells, and the transformation of fibroblasts to myofibroblasts. Recent studies suggest that EMT is a key factor in the pathogenesis of pulmonary fibrosis, as the disruption of EMT-related effector molecules can inhibit the occurrence and development of PF. With the numerous advancements made in molecular biology in recent years, researchers have discovered that exosomes and their cargos, such as miRNAs, lncRNAs, and proteins, can promote or inhibit the EMT, modulate the transformation of fibroblasts into myofibroblasts, contribute to the proliferation of fibroblasts and promote immunoregulatory and mitochondrial damage during pulmonary fibrosis. Exosomes are key factors regulating the differentiation of bone marrow mesenchymal stem cells (BMSCs) into myofibroblasts. Interestingly, exosomes derived from BMSCs under pathological and physiological conditions may promote or inhibit the EMT of type II alveolar epithelial cells and the transformation of fibroblasts into myofibroblasts to regulate pulmonary fibrosis. Thus, exosomes may become a new direction in the study of drugs for the treatment of pulmonary fibrosis.

Brain delivery of quercetin-loaded exosomes improved cognitive function in AD mice by inhibiting phosphorylated tau-mediated neurofibrillary tangles

It is reported that quercetin (Que) can prevent tau pathology and induce neuroprotection by improving cognitive and functional symptoms in the treatment of Alzheimer's disease (AD). However, its clinical application has been limited due to its poor brain targeting and bioavailability. Exosomes are considered as cargo carriers for intercellular communication and especially serve as a natural and important drug brain delivery platform for achieving better treatment of central neurological diseases. Here, we developed plasma exosomes (Exo) loaded with Que (Exo-Que) to improve the drug bioavailability, enhance the brain targeting of Que and potently ameliorate cognitive dysfunction in okadaic acid (OA)-induced AD mice. Our results showed that Exo-Que improved brain targeting of Que as well as significantly enhanced bioavailability of Que. Furthermore, compared with free Que, Exo-Que better relieved the symptoms of AD by inhibiting cyclin-dependent kinase 5 (CDK5)-mediated phosphorylation of Tau and reducing formation of insoluble neurofibrillary tangles (NFTs), suggesting its therapeutic potential for better treatment of AD.

Extracellular vesicles: A bright star of nanomedicine

Extracellular vesicles (EVs) have unique structural, compositional, and morphological characteristics as well as predominant physiochemical stability and biocompatibility properties. They play a crucial role in pathophysiological regulation, and also have broad prospects for clinical application in the diagnosis, prognosis, and therapy of disease, and tissue regeneration and repair. Herein, the biosynthesis and physiological functions and current methods for separation and identification of EVs are summarized. Specifically, engineered EVs may be used to enhance targeted therapy in cancer and repair damaged tissues, and they may be developed as an individualized imaging diagnostic reagent, among other potential applications. We will focus on reviewing recent studies on engineered EVs in which alterations enhanced their therapeutic capability or diagnostic imaging potential via physical, chemical, and biological modification approaches. This review will clarify the superior biological functions and powerful therapeutic potential of EVs, particularly with regard to new designs based on EVs and their utilization in a new generation of nanomedicine diagnosis and treatment platforms.

Recent Advances in Extracellular Vesicles as Drug Delivery Systems and Their Potential in Precision Medicine

Extracellular vesicles (EVs) are membrane-bilayered nanoparticles released by most cell types. Recently, an enormous number of studies have been published on the potential of EVs as carriers of therapeutic agents. In contrast to systems such as liposomes, EVs exhibit less immunogenicity and higher engineering potential. Here, we review the most relevant publications addressing the potential and use of EVs as a drug delivery system (DDS). The information is divided based on the key steps for designing an EV-mediated delivery strategy. We discuss possible sources and isolation methods of EVs. We address the administration routes that have been tested in vivo and the tissue distribution observed. We describe the current knowledge on EV clearance, a significant challenge towards enhancing bioavailability. Also, EV-engineering approaches are described as alternatives to improve tissue and cell-specificity. Finally, a summary of the ongoing clinical trials is performed. Although the application of EVs in the clinical practice is still at an early stage, a high number of studies in animals support their potential as DDS. Thus, better treatment options could be designed to precisely increase target specificity and therapeutic efficacy while reducing off-target effects and toxicity according to the individual requirements of each patient.

RNA delivery by extracellular vesicles in mammalian cells and its applications

The term 'extracellular vesicles' refers to a heterogeneous population of vesicular bodies of cellular origin that derive either from the endosomal compartment (exosomes) or as a result of shedding from the plasma membrane (microvesicles, oncosomes and apoptotic bodies). Extracellular vesicles carry a variety of cargo, including RNAs, proteins, lipids and DNA, which can be taken up by other cells, both in the direct vicinity of the source cell and at distant sites in the body via biofluids, and elicit a variety of phenotypic responses. Owing to their unique biology and roles in cell-cell communication, extracellular vesicles have attracted strong interest, which is further enhanced by their potential clinical utility. Because extracellular vesicles derive their cargo from the contents of the cells that produce them, they are attractive sources of biomarkers for a variety of diseases. Furthermore, studies demonstrating phenotypic effects of specific extracellular vesicle-associated cargo on target cells have stoked interest in extracellular vesicles as therapeutic vehicles. There is particularly strong evidence that the RNA cargo of extracellular vesicles can alter recipient cell gene expression and function. During the past decade, extracellular vesicles and their RNA cargo have become better defined, but many aspects of extracellular vesicle biology remain to be elucidated. These include selective cargo loading resulting in substantial differences between the composition of extracellular vesicles and source cells; heterogeneity in extracellular vesicle size and composition; and undefined mechanisms for the uptake of extracellular vesicles into recipient cells and the fates of their cargo. Further progress in unravelling the basic mechanisms of extracellular vesicle biogenesis, transport, and cargo delivery and function is needed for successful clinical implementation. This Review focuses on the current state of knowledge pertaining to packaging, transport and function of RNAs in extracellular vesicles and outlines the progress made thus far towards their clinical applications.

Preparing the Bone Tissue Regeneration Ground by Exosomes: From Diagnosis to Therapy

Bone tissue engineering employs acellular scaffolds or scaffolds, along with cells and growth factors, to provide the mechanical support needed, as well as serve as a delivery vehicle for bioactive molecules to the injury sites. As tissue engineering continues to evolve, it has integrated two emerging fields: stem cells and nanotechnology. A paracrine factor that is found to be responsible for the major regenerative effect in stem cell transplantation is an extracellular vesicle called an 'exosome'. Recent advances in nanotechnology have allowed the 'exosome' to be distinguished from other extracellular vesicles and be polymerized into a well-defined concept. Scientists are now investigating exosome uses in clinical applications. For bone-related diseases, exosomes are being explored as biomarkers for different bone pathologies. They are also being explored as a therapeutic agent where progenitor cell-derived exosomes are used to regenerate damaged bone tissue. In addition, exosomes are being tested as immune modulators for bone tissue inflammation, and finally as a delivery vehicle for therapeutic agents. This review discusses recently published literature on the clinical utilization of exosomes in bone-related applications and the correlated advantages. A particular focus will be placed on the potential utilization of regenerative cell-derived exosomes as a natural biomaterial for tissue regeneration.

Approaches to promoting bone marrow mesenchymal stem cell osteogenesis on orthopedic implant surface

Bone marrow-derived mesenchymal stem cells (BMSCs) play a critical role in the osseointegration of bone and orthopedic implant. However, osseointegration between the Ti-based implants and the surrounding bone tissue must be improved due to titanium’s inherent defects. Surface modification stands out as a versatile technique to create instructive biomaterials that can actively direct stem cell fate. Here, we summarize the current approaches to promoting BMSC osteogenesis on the surface of titanium and its alloys. We will highlight the utilization of the unique properties of titanium and its alloys in promoting tissue regeneration, and discuss recent advances in understanding their role in regenerative medicine. We aim to provide a systematic and comprehensive review of approaches to promoting BMSC osteogenesis on the orthopedic implant surface.

MicroRNA-29b Promotes Subchondral Bone Loss in TMJ Osteoarthritis

Abnormal subchondral bone remodeling plays important roles during osteoarthritis (OA) pathology. Recent studies show that bone marrow mesenchymal stem cells (BMSCs) in osteoarthritic subchondral bones exhibit a prominent pro-osteoclastic effect that contributes to abnormal subchondral bone remodeling; however, the pathologic mechanism remains unclear. In the present study, we used a mouse model with OA-like change in the temporomandibular joint (TMJ) induced by an experimentally unilateral anterior crossbite (UAC) and found that the level of microRNA-29b (miR-29b), but not miR-29a or miR-29c, was markedly lower in BMSCs from subchondral bones of UAC mice as compared with that from the sham control mice. With an intra-articular aptamer delivery system, BMSC-specific overexpression of miR-29b by aptamer-agomiR-29b rescued subchondral bone loss and osteoclast hyperfunction in UAC mice, as demonstrated by a significant increase in bone mineral density, bone volume fraction, trabecular thickness, and the gene expression of osteocalcin and Runx2 but decreased trabecular separation, osteoclast number and osteoclast surface/bone surface, and the gene expression of cathepsin K, Trap, Wnt5a, Rankl, and Rank as compared with those in the UAC mice treated by aptamer-NC (all P < 0.05). In addition, BMSC-specific inhibition of miR-29b by aptamer-antagomiR-29b exacerbated those responses in UAC mice. Notably, although it primarily affected miR-29b levels in the subchondral bone (but not in cartilage and synovium), BMSC-specific overexpression of miR-29b in UAC mice largely rescued OA-like cartilage degradation, including decreased chondrocyte density, cartilage thickness, and the percentage areas of proteoglycans and type II collagen, while BMSC-specific inhibition of miR-29b aggravated these characteristics of cartilage degradation in UAC mice. Moreover, we identified Wnt5a, but not Rankl or Sdf-1, as the direct target of miR-29b. The results of the present study indicate that miR-29b is a key regulator of the pro-osteoclastic effects of BMSCs in TMJ-OA subchondral bones and plays important roles in the TMJ-OA progression.

A photo-triggerable aptamer nanoswitch for spatiotemporal controllable siRNA delivery

A photo-triggerable aptamer nanoswitch was proposed for spatiotemporal regulation of siRNA delivery. Recognition between AS1411 and nucleolin was effectively blocked by a photo-labile complementary oligonucleotide, which could be reactivated with photo-irradiation, resulting in efficient tumor-targeted siRNA internalization and gene silencing in vitro and in vivo.

Saliva exosomes-derived UBE2O mRNA promotes angiogenesis in cutaneous wounds by targeting SMAD6

Background

Enhancing angiogenesis is critical for accelerating wound healing. Application of different types of exosomes (Exos) to promote angiogenesis represents a novel strategy for enhanced wound repair. Saliva is known to accelerate wound healing, but the underlying mechanisms remain unclear.

Results

Our results have demonstrated that saliva-derived exosomes (saliva-Exos) induce human umbilical vein endothelial cells (HUVEC) proliferation, migration, and angiogenesis in vitro, and promote cutaneous wound healing in vivo. Further experiments documented that Ubiquitin-conjugating enzyme E2O (UBE2O) is one of the main mRNAs of saliva-Exos, and activation of UBE2O has effects similar to those of saliva-Exos, both in vitro and in vivo. Mechanistically, UBE2O decreases the level of SMAD family member 6 (SMAD6), thereby activating bone morphogenetic protein 2 (BMP2), which, in turn, induces angiogenesis.

Conclusions

The present work suggests that administration of saliva-Exos and UBE2O represents a promising strategy for enhancing wound healing through promotion of angiogenesis.

Recent advances of aptasensors for exosomes detection

Exosomes are nanoscale phospholipid bilayer membrane-enclosed vesicles released from cells with diameters of 30-150 nm. Their contents reflect significant information regarding the cancer microenvironment from their parent cells, which attracts increasing attention as potential biomarkers for noninvasive early diagnosis. Among their detection methods, aptasensor has been becoming an attractive star with its properties of affordability, easy to use, fast response, high sensitivity, remarkable specificity, and multiplexing capability. This review mainly summarizes the recent advances of single-stranded DNA (ssDNA) aptamer-based sensors for cancer and tumor-derived exosomes detection. Firstly, we present a brief overview of aptamers and exosomes. Then, we introduce the exosomal proteins used as potential biomarkers of various cancers, and their specific ssDNA aptamers used in aptasensors. We emphasize eight major types of aptasensors: fluorescent, electrochemical, colorimetric, luminescence, lateral flow strips, surface-enhanced Raman scattering, surface plasmon resonance, and giant magnetoresistance sensors, based on fabrication methods, bio-recognition mechanism, as well as detection evaluation. The future directions and challenges are finally proposed for aptamers and their more applications in exosomes research.

Interests of Exosomes in Bone and Periodontal Regeneration: A Systematic Review

Periodontitis is an infectious inflammatory disease characterized by clinical attachment loss and tooth supporting tissue destruction. As exosomes demonstrated pro-regenerative ability, their use in periodontal treatment has been suggested. The aim of this systematic review is to gather and summarize the most recent data regarding exosomes to determine their potential impact in bone and periodontal regeneration. Electronic databases (Pubmed, Web of Science) were searched up to February 2020. Studies assessing the impact of exosomes administration in experimental bone and periodontal defects have been identified according to PRISMA guidelines. Among the 183 identified articles, 16 met the inclusion criteria and were included in this systematic review. Experimental bone defects were mainly surgically induced with a dental bur or distraction tools. All studies considered bone healing after exosomes administration as the primary outcome. Results showed that mesenchymal stem cells derived exosomes administration promoted bone healing and neovascularization. Nevertheless, a dose-effect relationship was observed. Exosomes administration appears to promote significantly the bone healing and periodontal regeneration. However, only a limited number of studies have been carried out so far and the optimized protocols in this context need to be evaluated.