Exosomes derived from human embryonic mesenchymal stem cells promote osteochondral regeneration

On the Choice of the Extracellular Vesicles for Therapeutic Purposes

Extracellular vesicles (EVs) are lipid membrane vesicles released by all human cells and are widely recognized to be involved in many cellular processes, both in physiological and pathological conditions. They are mediators of cell-cell communication, at both paracrine and systemic levels, and therefore they are active players in cell differentiation, tissue homeostasis, and organ remodeling. Due to their ability to serve as a cargo for proteins, lipids, and nucleic acids, which often reflects the cellular source, they should be considered the future of the natural nanodelivery of bio-compounds. To date, natural nanovesicles, such as exosomes, have been shown to represent a source of disease biomarkers and have high potential benefits in regenerative medicine. Indeed, they deliver both chemical and bio-molecules in a way that within exosomes drugs are more effective that in their exosome-free form. Thus, to date, we know that exosomes are shuttle disease biomarkers and probably the most effective way to deliver therapeutic molecules within target cells. However, we do not know exactly which exosomes may be used in therapy in avoiding side effects as well. In regenerative medicine, it will be ideal to use autologous exosomes, but it seems not ideal to use plasma-derived exosomes, as they may contain potentially dangerous molecules. Here, we want to present and discuss a contradictory relatively unmet issue that is the lack of a general agreement on the choice for the source of extracellular vesicles for therapeutic use.

Exosomes and Bone Disease

Exosomes, which mediate cell-to-cell communications and provide a novel insight into information exchange, have drawn increasing attention in recent years. The homeostasis of bone metabolism is critical for bone health. The most common bone diseases such as osteoporosis, osteoarthritis and bone fractures have apparent correlations with exosomes. Accumulating evidence has suggested the potential regenerative capacities of stem cell-derived exosomes. In this review, we summarise the pathophysiological mechanism, clinical picture and therapeutic effects of exosomes in bone metabolism. We introduce the advantages and challenges in the application of exosomes. Although the exact mechanisms remain unclear, miRNAs seem to play major roles in the exosome.

Minimally Invasive and Regenerative Therapeutics

Advances in biomaterial synthesis and fabrication, stem cell biology, bioimaging, microsurgery procedures, and microscale technologies have made minimally invasive therapeutics a viable tool in regenerative medicine. Therapeutics, herein defined as cells, biomaterials, biomolecules, and their combinations, can be delivered in a minimally invasive way to regenerate different tissues in the body, such as bone, cartilage, pancreas, cardiac, skeletal muscle, liver, skin, and neural tissues. Sophisticated methods of tracking, sensing, and stimulation of therapeutics in vivo using nano-biomaterials and soft bioelectronic devices provide great opportunities to further develop minimally invasive and regenerative therapeutics (MIRET). In general, minimally invasive delivery methods offer high yield with low risk of complications and reduced costs compared to conventional delivery methods. Here, minimally invasive approaches for delivering regenerative therapeutics into the body are reviewed. The use of MIRET to treat different tissues and organs is described. Although some clinical trials have been performed using MIRET, it is hoped that such therapeutics find wider applications to treat patients. Finally, some future perspective and challenges for this emerging field are highlighted.

Extracellular vesicles for personalized medicine: The input of physically triggered production, loading and theranostic properties

Emerging advances in extracellular vesicle (EV) research brings along new promises for tailoring clinical treatments in order to meet specific disease features of each patient in a personalized medicine concept. EVs may act as regenerative effectors conveying endogenous therapeutic factors from parent cells or constitute a bio-camouflaged delivery system for exogenous therapeutic agents. Physical stimulation may be an important tool in the field of EVs for personalized therapy by powering EV production, loading and therapeutic properties. Physically-triggered EV production is inspired by naturally occurring EV release by shear stress in blood vessels. Bioinspired physically-triggered EV production technologies may bring along high yield advantages combined to scalability assets. Physical stimulation may also provide new prospects for high-efficient EV loading. Additionally, physically-triggered EV theranostic properties brings new hopes for spatio-temporal controlled therapy combined to tracking. Technological considerations related to EV-based personalized medicine and the input of physical stimulation on EV production, loading and theranostic properties will be overviewed herein.

Role of Mesenchymal Stem Cells—Derived Exosomes in Osteoarthritis Treatment

Exosomes are nanovesicles that are involved in inter-cellular communication and are secreted by many types of cells. Exosomes secreted by stem cells can effectively transport bioactive proteins, messenger ribonucleic acids (mRNAs) and microribonucleic acids (miRNAs) organelles and play important roles in intercellular communication and the regulation of tissue regeneration. This transfer of bioactive molecules plays a main role in: tumor invasion and metastasis, immune and inflammation modulation, epithelial-mesenchymal transition and neurobiology. Mesenchymal Stem Cells (MSC) exosomes provide new perspectives for the development of an off-the-shelf and cell-free MSC therapy for the treatment of cartilage injuries and osteoarthritis. This report describes the progress in exosome studies and potential clinical use for osteoarthritis treatment.

THE EFFECT OF MESENCHYMAL STEM CELL DERIVED MICROVESICLES IN REPAIR OF FEMORAL CHONDRAL DEFECTS IN DOGS

Mesenchymal stem cells (MSCs) releases in culture extracellular vesicles called microvesicles (MVs). MVs have beneficial cytokines that prevent progression of the disease and help in the regeneration process. This study is aimed to evaluate the effect of MSCs derived MVs in repair of induced chondral defect in a dog model. Methods: Chondral defects were created surgically ([Formula: see text][Formula: see text]mm) in both femoral condyles of nine dogs, autologous MSCs were isolated and MVs were prepared and injected intraarticularly in the right joint. The left joint was injected with normal saline as control negative. Evaluation of the treatment after first injection was carried out by physical examination and histopathology at different time periods ([Formula: see text]½, 3 and 6 months). Results: Treated joints showed marked degree of cartilage regeneration and restoration of chondral histomorphological picture on the contrary of the control joints that showed deterioration over time and defect filling with only fibrous tissue forming a fibrocartilage at the end of six months period. Conclusion: We demonstrated in this study that administration of MVs was effective on the functional and morphological recovery of the injured cartilage and could be exploited as a cell free therapeutic approach in regenerative medicine.

Roles and Regulation of Extracellular Vesicles in Cardiovascular Mineral Metabolism

Cardiovascular calcification is a multifaceted disease that is a leading independent predictor of cardiovascular morbidity and mortality. Recent studies have identified a calcification-prone population of extracellular vesicles as the putative elementary units of vascular microcalcification in diseased heart valves and vessels. Their action is highly context-dependent; extracellular vesicles released by smooth muscle cells, valvular interstitial cells, endothelial cells, and macrophages may promote or inhibit mineralization, depending on the phenotype of their originating cells and/or the extracellular environment to which they are released. In particular, emerging roles for vesicular microRNAs, bioactive lipids, metabolites, and protein cargoes in driving this pro-calcific switch underpin the necessity of innovative strategies to employ next-generation sequencing and omics technologies in order to better understand the pathobiology of these nano-sized entities. Furthermore, a recent body of work has emerged that centers on the novel re-purposing of extracellular vesicles and exosomes as potential therapeutic avenues for cardiovascular calcification. This review aims to highlight the role of extracellular vesicles as constituents of cardiovascular calcification and summarizes recent advances in our understanding of the biophysical nature of vesicle accumulation, aggregation, and mineralization. We also comprehensively discuss the latest evidence that extracellular vesicles act as key mediators and regulators of cell/cell communication, osteoblastic/osteoclastic differentiation, and cell/matrix interactions in cardiovascular tissues. Lastly, we highlight the importance of robust vesicle isolation and characterization when studying these phenomena, and offer a brief primer on working with cardiovascular applications of extracellular vesicles.

Osteogenic effect of bone marrow mesenchymal stem cell-derived exosomes on steroid-induced osteonecrosis of the femoral head

BACKGROUND

Animal studies have demonstrated the therapeutic effect of mesenchymal stem cells (MSCs) on osteogenesis, but little is known about the functions of exosomes (Exos) released by bone MSCs (BMSCs). Here, we investigated the effect of BMSC Exos on steroid-induced femoral head necrosis (SFHN) and explored the vital genes involved in this process.

MATERIALS AND METHODS

BMSCs were isolated from healthy and SFHN rats. BMSC Exos were isolated using the Exosome Precipitation Kit and characterized by transmission electron microscopy and Western blotting. SFHN BMSCs were incubated with Exos from healthy BMSCs. Osteogenic ability was assessed by oil red O staining and alizarine red staining. Differentially expressed genes (DEGs) induced by Exos were screened using the Osteogenesis RT2 Profiler PCR Array. The effect of upregulated Sox9 was examined using lentivirus-mediated siRNA.

RESULTS

The results revealed that BMSC Exos were 100-150 nm in size and expressed CD63. Moreover, BMSC Exo-treated SFHN cells exhibited suppressed adipogenesis compared to model cells. PCR array showed that eleven and nine genes were upregulated and downregulated, respectively, in the BMSC Exo-treated SFHN cells compared to the model group. Among the DEGs, osteogenesis-related genes, including Bmp2, Bmp6, Bmpr1b, Mmp9, and Sox9, may play important roles in SFHN. Furthermore, the DEGs were mainly involved in immune response, osteoblast differentiation, and in the transforming growth factor-β/bone morphogenetic protein signaling pathway. The level of the SOX9 protein was upregulated by Exos, and Sox9 silencing significantly decreased the osteogenic effect of BMSC Exos.

CONCLUSION

Our data suggest that Exos derived from BMSCs mainly affect SFHN osteogenesis, and this finding can be further investigated to develop a novel therapeutic agent for SFHN.

Extracellular vesicles in synovial fluid from juvenile horses: No age-related changes in the quantitative profile

Extracellular vesicle (EV) concentration, characteristics and function in equine synovial fluid (SF) during normal growth and development has not previously been studied. Isolation of EVs was performed in SF from three healthy foals and two adult horses by differential ultracentrifugation (10,000g and 200,000g); EVs were purified by sucrose density gradient floatation and analysed by high-resolution flow cytometry (FCM), buoyant density and western blotting. Additionally, repeated biomarker analysis of sulphated glycosaminoglycans (GAG), matrix metalloproteinase (MMP), C-terminal crosslinked telopeptide type II collagen (CTX-II), collagenase cleaved neopeptide type II collagen (C2C) was performed in SF from 10 foals and six adult horses. In contrast with the quantitative EV profile, the biomarker profile in SF from juvenile joints was substantially different from that in SF from adult animals. However, there were qualitative differences in the high-resolution FCM scatter plots. Future in-depth functional analyses may reveal differences between juvenile and mature EVs in SF.

Exosomal KLF3-AS1 from hMSCs promoted cartilage repair and chondrocyte proliferation in osteoarthritis

The present study was designed to explore whether exosomal lncRNA-KLF3-AS1 derived from human mesenchymal stem cells (hMSCs) can serve as a positive treatment for osteoarthritis (OA). hMSCs and MSC-derived exosomes (MSC-exo) were prepared for morphological observation and identification by transmission electron microscopy and flow cytometry. IL-1β-induced OA chondrocytes and collagenase-induced rat model of OA were established for the further experiments. Lentivirus-mediated siRNA targeting KLF3-AS1 was transfected into MSCs for silencing KLF3-AS1. The real-time quantitative PCR and western blotting analysis were performed to examine the mRNA and protein levels of type II collagen alpha 1 (Col2a1), aggrecan, matrix metalloproteinase 13 and runt-related transcription factor 2. Cell proliferation, apoptosis and migration were evaluated by CCK-8 assay, flow cytometry and transwell assay. HE (hematoxylin and eosin) staining and immunohistochemistry were used for histopathological studies. MSC-exo ameliorated IL-1β-induced cartilage injury. Furthermore, lncRNA KLF3-AS1 was markedly enriched in MSC-exo, and exosomal KLF3-AS1 suppressed IL-1β-induced apoptosis of chondrocytes. Further in vivo investigation indicated that exosomal KLF3-AS1 promoted cartilage repair in a rat model of OA. Exosomal KLF3-AS1 promoted cartilage repair and chondrocyte proliferation in a rat model of OA, which might be an underlying therapeutic target for OA.

Exosomes derived from mature chondrocytes facilitate subcutaneous stable ectopic chondrogenesis of cartilage progenitor cells

BACKGROUND

Developing cartilage constructed with the appropriate matrix composition and persistent chondrogenesis remains an enduring challenge in cartilage defects. Cartilage progenitor cell (CPC)-based tissue engineering has attracted recent attention because of its strong chondrogenic differentiation capacity. However, due to the lack of a suitable chondrogenic niche, the clinical application of CPC-regenerated cartilage in the subcutaneous environment remains a challenge. In this study, exosomes derived from chondrocytes (CC-Exos) were used to provide the CPC constructs with a cartilage signal in subcutaneous environments for efficient ectopic cartilage regeneration.

METHODS

Rabbit CPC-alginate constructs were prepared and implanted subcutaneously in nude mice. CC-Exos were injected into the constructs at the same dose (30 μg exosomes per 100 μL injection) after surgery and thereafter weekly for a period of 12 weeks. Exosomes derived from bone mesenchymal stem cells (BMSC-Exos) were used as the positive control. The mice in the negative control were administered with the same volume of PBS. At 4 and 12 weeks after implantation, the potential of CC-Exos and BMSC-Exos to promote chondrogenesis and stability of cartilage tissue in a subcutaneous environment were analyzed by histology, immunostaining, and protein analysis. The influences of BMSC-Exos and CC-Exos on chondrogenesis and angiogenic characteristics in vitro were assessed via coculturing with CPCs and human umbilical vein endothelial cells.

RESULTS

The CC-Exos injection increased collagen deposition and minimized vascular ingrowth in engineered constructs, which efficiently and reproducibly developed into cartilage. The generated cartilage was phenotypically stable with minimal hypertrophy and vessel ingrowth up to 12 weeks, while the cartilage formed with BMSC-Exos was characterized by hypertrophic differentiation accompanied by vascular ingrowth. In vitro experiments indicated that CC-Exos stimulated CPCs proliferation and increased expression of chondrogenesis markers while inhibiting angiogenesis.

CONCLUSIONS

These findings suggest that the novel CC-Exos provides the preferable niche in directing stable ectopic chondrogenesis of CPCs. The use of CC-Exos may represent an off-the-shelf and cell-free therapeutic approach for promoting cartilage regeneration in the subcutaneous environment.

Extracellular Vesicles in Joint Disease and Therapy

The use of extracellular vesicles (EVs) as a potential therapy is currently explored for different disease areas. When it comes to the treatment of joint diseases this approach is still in its infancy. As in joint diseases both inflammation and the associated articular tissue destruction are important factors, both the immune-suppressive and the regenerative properties of EVs are potentially advantageous characteristics for future therapy. There is, however, only limited knowledge on the basic features, such as numerical profile and function, of EVs in joint articular tissues in general and their linking medium, the synovial fluid, in particular. Further insight is urgently needed in order to appreciate the full potential of EVs and to exploit these in EV-mediated therapies. Physiologic joint homeostasis is a prerequisite for proper functioning of joints and we postulate that EVs play a key role in the regulation of joint homeostasis and hence can have an important function in re-establishing disturbed joint homeostasis, and, in parallel, in the regeneration of articular tissues. In this mini-review EVs in the joint are explained from a historical perspective in both health and disease, including the potential niche for EVs in articular tissue regeneration. Furthermore, the translational potential of equine models for human joint biology is discussed. Finally, the use of MSC-derived EVs that is recently gaining ground is highlighted and recommendations are given for further EV research in this field.

MSC-derived exosomes promote proliferation and inhibit apoptosis of chondrocytes via lncRNA-KLF3-AS1/miR-206/GIT1 axis in osteoarthritis

BACKGROUND

Exosomes secreted by human mesenchymal stem cells (hMSCs) have been shown to promote cartilage regeneration. This study aimed to explore whether exosomal lncRNA-KLF3-AS1 derived from hMSCs can promote chondrocyte proliferation via miR-206/GIT1 axis in osteoarthritis (OA).

METHODS

hMSCs and MSC-derived exosomes (MSC-exo) were prepared for morphological observation and identification by transmission electron microscopy (TEM) and flow cytometry. IL-1β-induced OA chondrocytes and collagenase-induced mouse OA model were established for the further experiments. Luciferase activity assay was performed to test whether miR-206 could bind to KLF3-AS1 or GIT1. Cell proliferation and apoptosis were evaluated by CCK-8 assay and flow cytometry, respectively.

RESULTS

MSC-Exos increased chondrogenic genes Col2a1 (type II collagen alpha 1) and aggrecan, decreased hondrocyte hypertrophy markers MMP-13 (matrix metalloproteinase-13) and Runx2 (runt-related transcription factor 2) in chondrocytes isolated from OA model mice. Furthermore, MSC-Exos attenuated IL-1β-induced chondrocyte proliferation inhibition and apoptosis induction. Moreover, MSC^KLF3-AS1-Exos (exosomes derived from KLF3-AS1-overexpressing-MSCs) ameliorated IL-1β-induced chondrocyte injury. Results also demonstrated that KLF3-AS1 acted as a competitive endogenous RNA (ceRNA) by sponging miR-206 to facilitate GIT1 expression. In addition, miR-206 overexpression and GIT1 knockdown reversed MSC^KLF3-AS1-Exos-mediated attenuation of chondrocyte injury.

CONCLUSION

Exosomal KLF3-AS1 derived from MSCs involved in MSC-Exos-mediated chondrocyte proliferation induction and chondrocyte apoptosis inhibition via miR-206/GIT1 axis. Abbreviation: G-protein-coupled receptor kinase interacting protein-1 (GIT1).

Exosomes in inflammation and role as biomarkers

Exosomes are endosomal-derived nano-vesicles. They are considered vehicles through which donor cells transfer proteins, lipids and nucleic acids to target cells thus influencing their metabolism. Exosomes are involved in inflammatory processes that play a pivotal role in a large number of pathologic states including cancer, inflammatory bowel diseases, type 2 diabetes, obesity, rheumatoid arthritis and neurodegenerative diseases. The association between inflammation and change in nature or expression level of some exosomal cargos is the fundamental step for identifying possible novel biomarkers of inflammatory-based diseases. A novel interesting exosome cargo is the SLC22A5 transport protein whose level in exosomes is regulated by the pro-inflammatory cytokine INF-γ. The advantage of using exosomes as a biomarker vehicle consists of their ease of collection from body fluids such as urine and saliva as they may represent a non-invasive means for screening human pathology.

Extracellular vesicle and mesenchymal stem cells in bone regeneration: recent progress and perspectives

Transplanting mesenchymal stem cells (MSCs) has been widely perceived as an ideal treatment for bone repair and regeneration, owing to their differential potential. However, researchers found that very few intravenous MSCs could stay in the target tissue, whereas the majority of them are trapped in liver, spleen, and lung, largely reducing its therapeutic effects. Recently, extracellular vesicles (EVs) have attracted increased attention due to their function in bone repair and advantages over traditional cell therapy. Also, MSCs-derived EVs are likely to achieve the osteogenic goal via modulating the cells and cytokines involved in bone metabolism. This review aims at summarizing the function of EVs and MSCs in bone metabolism and regeneration. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 243-250, 2019.

Applications of stem cell-derived exosomes in tissue engineering and neurological diseases

Exosomes are extracellular vesicles with diameters of 30-100 nm that are key for intercellular communication. Almost all types of cell, including dendritic cells, T cells, mast cells, epithelial cells, neuronal cells, adipocytes, mesenchymal stem cells, and platelets, can release exosomes. Exosomes are present in human body fluids, such as urine, amniotic fluid, malignant ascites, synovial fluid, breast milk, cerebrospinal fluid, semen, saliva, and blood. Exosomes have biological functions in immune response, antigen presentation, intercellular communication, and RNA and protein transfer. This review provides a brief overview of the origin, morphological characteristics, enrichment and identification methods, biological functions, and applications in tissue engineering and neurological diseases of exosomes.

Immune regulatory targets of mesenchymal stromal cell exosomes/small extracellular vesicles in tissue regeneration

Mesenchymal stromal cell (MSC) therapies have demonstrated therapeutic efficacy in a wide-ranging array of tissue injury and disease indications. An important aspect of MSC-mediated therapeutic activities is immune modulation. Consistent with the concentration of MSC therapeutic potency in its secretion, a significant proportion of MSC immune potency resides in the small extracellular vesicles (sEVs) secreted by MSCs. These sEVs, which also include exosomes, carry a large cargo enriched in proteins with potent immunomodulatory activities. They have been reported to exert potent effects on humoral and cellular components of the immune system in vitro and in vivo, and may have the potential to support the diametrically opposite pro- and anti-inflammatory functions necessary for tissue repair and regeneration following injury. Following injury, pro-inflammatory activities are necessary to neutralize injury and remove dead or injured tissue, while anti-inflammatory activities to facilitate migration and proliferation of reparative cell types and to increase vascularization and nutrient supply are necessary to repair and regenerate new tissue. Therefore, a critical immunomodulatory requisite of MSC sEVs in tissue regeneration is the capacity to support the appropriate immune activities at the appropriate time. Here, we review how some of the immune regulatory targets of MSC sEVs could support the dynamic immunomodulatory activities during tissue repair and regeneration.

NANOmetric BIO-Banked MSC-Derived Exosome (NANOBIOME) as a Novel Approach to Regenerative Medicine

Mesenchymal stem cells (MSCs) are well known for their great potential in clinical applications. In fact, MSCs can differentiate into several cell lineages and show paracrine behavior by releasing endogenous factors that stimulate tissue repair and modulate local immune response. Each MSC type is affected by specific biobanking issues-technical issues as well as regulatory and ethical concerns-thus making it quite tricky to safely and commonly use MSC banking for swift regenerative applications. Extracellular vesicles (EVs) include a group of 150⁻1000 nm vesicles that are released by budding from the plasma membrane into biological fluids and/or in the culture medium from varied and heterogenic cell types. EVs consist of various vesicle types that are defined with different nomenclature such as exosomes, shedding vesicles, nanoparticles, microvesicles and apoptotic bodies. Ectosomes, micro- and nanoparticles generally refer to the direct release of single vesicles from the plasma membrane. While many studies describe exosomes as deriving from multivesicular bodies, solid evidence about the origin of EVs is often lacking. Extracellular vesicles represent an important portion of the cell secretome. Their numerous properties can be used for diagnostic, prognostic, and therapeutic uses, so EVs are considered to be innovative and smart theranostic tools. The aim of this review is to investigate the usefulness of exosomes as carriers of the whole information panel characterizing the use of MSCs in regenerative medicine. Our purpose is to make a step forward in the development of the NANOmetric BIO-banked MSC-derived Exosome (NANOBIOME).

Therapeutic Potential of Mesenchymal Cell-Derived miRNA-150-5p-Expressing Exosomes in Rheumatoid Arthritis Mediated by the Modulation of MMP14 and VEGF

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial tissue inflammation and joint destruction associated with the activation of angiogenesis. Exosomes, which play a role in cell-to-cell communication as carriers of genetic information, transfer microRNAs (miRNAs or miRs) between cells and have been studied as delivery vehicles for therapeutic molecules. The aim of the current study was to investigate the therapeutic effect of mesenchymal stem cell (MSC)-derived miR-150-5p exosomes on joint destruction in RA. The expression and secretion of miR-150-5p, matrix metalloproteinase (MMP) 14, and vascular endothelial growth factor (VEGF) in RA patients and fibroblast-like synoviocytes (FLS) were examined by quantitative RT-PCR, ELISA, and Western blotting. Immunohistochemistry was used to assess angiogenesis. MSCs were transfected with an miR-150-5p expression plasmid, and MSC-derived exosomes were harvested. The effect of MSC-derived miR-150-5p exosomes (Exo-150) on MMP14 and VEGF expression was examined. The effects of Exo-150 on cell migration and invasion in cytokine-stimulated FLS from RA patients were examined by HUVEC tube formation and transwell assays. The effect of Exo-150 in vivo was examined in a collagen-induced arthritis mouse model. Exo-150 decreased migration and invasion in RA FLS and downregulated tube formation in HUVECs by targeting MMP14 and VEGF. Injection of Exo-150 reduced hind paw thickness and the clinical arthritic scores in collagen-induced arthritis mice. Exo-150 reduced joint destruction by inhibiting synoviocyte hyperplasia and angiogenesis. Exosomes facilitate the direct intracellular transfer of miRNAs between cells and represent a potential therapeutic strategy for RA.

Exosomes derived from miR-92a-3p-overexpressing human mesenchymal stem cells enhance chondrogenesis and suppress cartilage degradation via targeting WNT5A

Background

WNT5A is known to be involved in the pathogenesis of osteoarthritis. This study investigated the molecular mechanism of exosomal miR-92a-3p and WNT5A in chondrogenesis and cartilage degeneration.

Methods

Exosomal miR-92a-3p expression was assessed in vitro in a human mesenchymal stem cell (MSC) model of chondrogenesis and in normal and OA primary human chondrocytes (PHCs). MSCs and PHCs were treated with exosomes derived from MSC-miR-92a-3p (MSC-miR-92a-3p-Exos) or its antisense inhibitor (MSC-anti-miR-92a-3p-Exos), respectively. Small interfering RNAs (siRNAs) and luciferase reporter assay were used to reveal the molecular role of exosomal miR-92a-3p and WNT5A in chondrogenesis. The protective effect of exosomes in vivo was measured using Safranin-O and Fast Green staining and immunohistochemical staining.

Results

Exosomal miR-92a-3p expression was elevated in the MSC chondrogenic exosome, while it was significantly reduced in the OA chondrocyte-secreted exosome compared with normal cartilage. Treatment with MSC-miR-92a-3p-Exos promoted cartilage proliferation and matrix genes expression in MSCs and PHCs, respectively. In contrast, treatment with MSC-anti-miR-92a-3p-Exos repressed chondrogenic differentiation and reduced cartilage matrix synthesis by enhancing the expression of WNT5A. Luciferase reporter assay demonstrated that miR-92a-3p suppressed the activity of a reporter construct containing the 3’-UTR and inhibited WNT5A expression in both MSCs and PHCs. MSC-miR-92a-3p-Exos inhibit cartilage degradation in the OA mice model.

Conclusions

Our results suggest that exosomal miR-92a-3p regulates cartilage development and homeostasis by directly targeting WNT5A. This indicates that exosomal miR-92a-3p may act as a Wnt inhibitor and exhibits potential as a disease-modifying osteoarthritis drug.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1004-0) contains supplementary material, which is available to authorized users.

Extracellular vesicles: intelligent delivery strategies for therapeutic applications

Extracellular vesicles (EV), in particular exosomes, have been the object of intense research, due to their potential to mediate intercellular communication, modulating the phenotype of target cells. The natural properties and functions of EV are being exploited as biomarkers for disease diagnosis and prognosis, and as nano-bio-carriers for the development of new therapeutic strategies. EV have been particularly examined in the field of cancer, but are also increasingly investigated in other areas, like immune-related diseases and regenerative medicine. In this review, the therapeutic use of EV as drug delivery systems is described, balancing the advantages and drawbacks of different routes for their in vivo administration. Systemic and local delivery of EV are discussed, tackling the persisting difficulties in the assessment of their pharmacokinetics, pharmacodynamics and biodistribution in vivo. Finally, we discuss the future perspectives for incorporating EV into delivery systems and their use for an improved and controlled release of EV in vivo.

Lab-on-Chip for Exosomes and Microvesicles Detection and Characterization

Interest in extracellular vesicles and in particular microvesicles and exosomes, which are constitutively produced by cells, is on the rise for their huge potential as biomarkers in a high number of disorders and pathologies as they are considered as carriers of information among cells, as well as being responsible for the spreading of diseases. Current methods of analysis of microvesicles and exosomes do not fulfill the requirements for their in-depth investigation and the complete exploitation of their diagnostic and prognostic value. Lab-on-chip methods have the potential and capabilities to bridge this gap and the technology is mature enough to provide all the necessary steps for a completely automated analysis of extracellular vesicles in body fluids. In this paper we provide an overview of the biological role of extracellular vesicles, standard biochemical methods of analysis and their limits, and a survey of lab-on-chip methods that are able to meet the needs of a deeper exploitation of these biological entities to drive their use in common clinical practice.

Bioprocessing of Mesenchymal Stem Cells and Their Derivatives: Toward Cell-Free Therapeutics

Mesenchymal stem cells (MSCs) have attracted tremendous research interest due to their ability to repair tissues and reduce inflammation when implanted into a damaged or diseased site. These therapeutic effects have been largely attributed to the collection of biomolecules they secrete (i.e., their secretome). Recent studies have provided evidence that similar effects may be produced by utilizing only the secretome fraction containing extracellular vesicles (EVs). EVs are cell-derived, membrane-bound vesicles that contain various biomolecules. Due to their small size and relative mobility, they provide a stable mechanism to deliver biomolecules (i.e., biological signals) throughout an organism. The use of the MSC secretome, or its components, has advantages over the implantation of the MSCs themselves: (i) signals can be bioengineered and scaled to specific dosages, and (ii) the nonliving nature of the secretome enables it to be efficiently stored and transported. However, since the composition and therapeutic benefit of the secretome can be influenced by cell source, culture conditions, isolation methods, and storage conditions, there is a need for standardization of bioprocessing parameters. This review focuses on key parameters within the MSC culture environment that affect the nature and functionality of the secretome. This information is pertinent to the development of bioprocesses aimed at scaling up the production of secretome-derived products for their use as therapeutics.

The complex landscape of microRNAs in articular cartilage: biology, pathology, and therapeutic targets

The disabling degenerative disease osteoarthritis (OA) is prevalent among the global population. Articular cartilage degeneration is a central feature of OA; therefore, a better understanding of the mechanisms that maintain cartilage homeostasis is vital for developing effective therapeutic interventions. MicroRNAs (miRs) modulate cell signaling pathways and various processes in articular cartilage via posttranscriptional repression of target genes. As dysregulated miRs frequently alter the homeostasis of articular cartilage, modulating select miRs presents a potential therapeutic opportunity for OA. Here, we review key miRs that have been shown to modulate cartilage-protective or -destructive mechanisms and signaling pathways. Additionally, we use an integrative computational biology approach to provide insight into predicted miR gene targets that may contribute to OA pathogenesis, and highlight the complexity of miR signaling in OA by generating both unique and overlapping gene targets of miRs that mediate protective or destructive effects. Early OA detection would enable effective prevention; thus, miRs are being explored as diagnostic biomarkers. We discuss these ongoing efforts and the applicability of miR mimics and antisense inhibitors as potential OA therapeutics.

Extracellular vesicles, exosomes and shedding vesicles in regenerative medicine - a new paradigm for tissue repair

Tissue regeneration by stem cells is driven by the paracrine activity of shedding vesicles and exosomes, which deliver specific cargoes to the recipient cells. Proteins, RNA, cytokines and subsequent gene expression, orchestrate the regeneration process by improving the microenvironment to promote cell survival, controlling inflammation, repairing injury and enhancing the healing process. The action of microRNA is widely accepted as an essential driver of the regenerative process through its impact on multiple downstream biological pathways, and its ability to regulate the host immune response. Here, we present an overview of the recent potential uses of exosomes for regenerative medicine and tissue engineering. We also highlight the differences in composition between shedding vesicles and exosomes that depend on the various types of stem cells from which they are derived. The conditions that affect the production of exosomes in different cell types are deliberated. This review also presents the current status of candidate exosomal microRNAs for potential therapeutic use in regenerative medicine, and in applications involving widely studied organs and tissues such as heart, lung, cartilage and bone.

Comparative efficacy of stem cells and secretome in articular cartilage regeneration: a systematic review and meta-analysis

Articular cartilage defect remains the most challenging joint disease due to limited intrinsic healing capacity of the cartilage that most often progresses to osteoarthritis. In recent years, stem cell therapy has evolved as therapeutic strategies for articular cartilage regeneration. However, a number of studies have shown that therapeutic efficacy of stem cell transplantation is attributed to multiple secreted factors that modulate the surrounding milieu to evoke reparative processes. This systematic review and meta-analysis aim to evaluate and compare the therapeutic efficacy of stem cell and secretome in articular cartilage regeneration in animal models. We systematically searched the PubMed, CINAHL, Cochrane Library, Ovid Medline and Scopus databases until August 2017 using search terms related to stem cells, cartilage regeneration and animals. A random effect meta-analysis of the included studies was performed to assess the treatment effects on new cartilage formation on an absolute score of 0-100% scale. Subgroup analyses were also performed by sorting studies independently based on similar characteristics. The pooled analysis of 59 studies that utilized stem cells significantly improved new cartilage formation by 25.99% as compared with control. Similarly, the secretome also significantly increased cartilage regeneration by 26.08% in comparison to the control. Subgroup analyses revealed no significant difference in the effect of stem cells in new cartilage formation. However, there was a significant decline in the effect of stem cells in articular cartilage regeneration during long-term follow-up, suggesting that the duration of follow-up is a predictor of new cartilage formation. Secretome has shown a similar effect to stem cells in new cartilage formation. The risk of bias assessment showed poor reporting for most studies thereby limiting the actual risk of bias assessment. The present study suggests that both stem cells and secretome interventions improve cartilage regeneration in animal trials. Graphical abstract ᅟ.

Three-Dimensional Spheroid Culture Increases Exosome Secretion from Mesenchymal Stem Cells

BACKGROUND

Mass production of exosomes is a prerequisite for their commercial utilization. This study investigated whether three-dimensional (3D) spheroid culture of mesenchymal stem cells (MSCs) could improve the production efficiency of exosomes and if so, what was the mechanism involved.

METHODS

We adopted two models of 3D spheroid culture using the hanging-drop (3D-HD) and poly(2-hydroxyethyl methacrylate) (poly-HEMA) coating methods (3D-PH). The efficiency of exosome production from MSCs in the 3D spheroids was compared with that of monolayer culture in various conditions. We then investigated the mechanism of the 3D spheroid culture-induced increase in exosome production.

RESULTS

The 3D-HD formed a single larger spheroid, while the 3D-PH formed multiple smaller ones. However, MSCs cultured on both types of spheroids produced significantly more exosomes than those cultured in conventional monolayer culture (2D). We then investigated the cause of the increased exosome production in terms of hypoxia within the 3D spheroids, high cell density, and non-adherent cell morphology. With increasing spheroid size, the efficiency of exosome production was the largest with the least amount of cells in both 3D-HD and 3D-PH. An increase in cell density in 2D culture (2D-H) was less efficient in exosome production than the conventional, lower cell density, 2D culture. Finally, when cells were plated at normal density on the poly-HEMA coated spheroids (3D-N-PH); they formed small aggregates of less than 10 cells and still produced more exosomes than those in the 2D culture when plated at the same density. We also found that the expression of F-actin was markedly reduced in the 3D-N-PH culture.

CONCLUSION

These results suggested that 3D spheroid culture produces more exosomes than 2D culture and the non-adherent round cell morphology itself might be a causative factor. The result of the present study could provide useful information to develop an optimal process for the mass production of exosomes.

Trophic Effects of Mesenchymal Stem Cells in Tissue Regeneration

Mesenchymal stem cells (MSCs) are considered to hold great therapeutic value for cell-based therapy and for tissue regeneration in particular. Recent evidence indicates that the main underlying mechanism for MSCs' beneficial effects in tissue regeneration is based on their capability to produce a large variety of bioactive trophic factors that stimulate neighboring parenchymal cells to start repairing damaged tissues. These new findings could potentially replace the classical paradigm of MSC differentiation and cell replacement. These bioactive factors have diverse actions like modulating the local immune system, enhancing angiogenesis, preventing cell apoptosis, and stimulating survival, proliferation, and differentiation of resident tissue specific cells. Therefore, MSCs are referred to as conductors of tissue repair and regeneration by secreting trophic mediators. In this review article, we have summarized the studies that focused on the trophic effects of MSC within the context of tissue regeneration. We will also highlight the various underlying mechanisms used by MSCs to act as trophic mediators. Besides the secretion of growth factors, we discuss two additional mechanisms that are likely to mediate MSC's beneficial effects in tissue regeneration, namely the production of extracellular vesicles and the formation of membrane nanotubes, which can both connect different cells and transfer a variety of trophic factors varying from proteins to mRNAs and miRNAs. Furthermore, we postulate that apoptosis of the MSCs is an integral part of the trophic effect during tissue repair.

Cartilage Regeneration in Humans with Adipose Tissue-Derived Stem Cells and Adipose Stromal Vascular Fraction Cells: Updated Status

Adipose tissue-derived stem cells (ASCs) in the form of stromal vascular fraction (SVF) and cultured expansion have been applied in clinical settings in some countries to treat osteoarthritis (OA) of knees, one of the most common debilitating, incurable disorders. Since the first report of successful cartilage-like tissue regeneration with autologous adipose SVF containing ASCs, there has been a gradual increase in the number of publications confirming such results. Thus far, most of the reports have been limited to treatments of OA of knees. Recently, successful applications of adipose SVF in treating OA of ankles and hips have been reported. In addition, several groups have reported modified methods of applying adipose SVF, such as combining bone marrow stimulation with adipose SVF or adding additional extracellular matrix (ECM) in treating OA. Here, we present an updated, systematic review of clinical effectiveness and safety in treating OA of knees, ankles, and one hip since 2016 using ASCs in the form of adipose SVF or in cultured expansion, along with a description and suggestion of potential biological mechanisms of cartilage regeneration.

MSC exosome works through a protein-based mechanism of action

Mesenchymal stem cell (MSC) exosome specifically defines the 50–200 nm vesicles that are secreted into the extracellular space when multivesicular bodies in the MSC fuse with the plasma membrane. However, the exosome is just one of several 50–200 nm extracellular vesicles (EVs) known to be secreted by cells. Nevertheless, the term ‘MSC exosome’ is often used to describe populations of 50–200 nm EVs that are prepared from culture medium conditioned by MSCs on the basis that these populations collectively exhibited typical exosome-associated proteins such as endosomal proteins, TSG101 and Alix, and tetraspanin proteins, CD9, CD63 and CD81. They also carry a rich diverse RNA cargo. MSC exosomes are increasingly implicated as the mediator of many of the MSC-associated therapeutic potencies. They elicit therapeutic activity by delivering their cargo of potentially therapeutic proteins and RNAs to the recipient cells. The therapeutic potency of MSC exosomes is usually rationalized on the presence of a biologically relevant protein or RNA in the MSC exosome. In the present paper, we expanded this rationale beyond a physical presence to include biologically relevant concentration, biochemical functionality and the potential to elicit an appropriate timely biochemical response. Based on these, we propose that MSC exosomes most probably work through the protein rather than the RNA.

Adipose-Derived Mesenchymal Stem Cells: Are They a Good Therapeutic Strategy for Osteoarthritis?

Osteoarthritis (OA) is a major cause of disability in elderly population around the world. More than one-third of people over 65 years old shows either clinical or radiological evidence of OA. There is no effective treatment for this degenerative disease, due to the limited capacity for spontaneous cartilage regeneration. Regarding the use of regenerative therapies, it has been reported that one option to restore degenerated cartilage are adipose-derived mesenchymal stem cells (ASCs). The purpose of this review is to describe and compare the efficacy of ASCs versus other therapies in OA. Methods: Recent studies have shown that ASCs exert paracrine effects protecting against degenerative changes in chondrocytes. According to the above, we have carried out a review of the literature using a combination of osteoarthritis, stem cells, and regenerative therapies as keywords. Results: Conventional pharmacological therapies for OA treatment are considered before the surgical option, however, they do not stop the progression of the disease. Moreover, total joint replacement is not recommended for patients under 55 years, and high tibia osteotomy (HTO) is a viable solution to address lower limb malalignment with concomitant OA, but some complications have been described. In recent years, the use of mesenchymal stem cells (MSCs) as a treatment strategy for OA is increasing considerably, thanks to their capacity to improve symptoms together with joint functionality and, therefore, the patients’ quality of life. Conclusions: ASC therapy has a positive effect on patients with OA, although there is limited evidence and little long-term follow-up.

A novel role in skeletal segment regeneration of extracellular vesicles released from periodontal-ligament stem cells

Purpose

The combination of oral derived stem cells and 3-D scaffolds is considered advantageous in bone repair. In particular, collagen membranes possess ideal biological properties and can support infiltration and proliferation of osteoblasts, promoting bone regeneration. Our study aimed to develop a new biocompatible osteogenic construct composed of a commercially available collagen membrane (Evolution [Evo]), human periodontal-ligament stem cells (hPDLSCs) enriched with extracellular vesicles (EVs), or polyethylenimine (PEI)-engineered EVs (PEI-EVs).

Methods

Osteogenic ability and expression of osteogenic genes were evaluated in vitro in hPDLSCs cultured with or without Evo, with Evo and EVs, or PEI-EVs. In addition, the bone-regeneration capacity of Evo, Evo enriched with hPDLSCs, Evo enriched with hPDLSCs and EVs/PEI-EVs was investigated in rats subjected to calvarial defects.

Results

Our results showed that Evo enriched with EVs and PEI-EVs showed high biocompatibility and osteogenic properties in vitro and in vivo. In addition, quantitative reverse-transcription polymerase chain reaction demonstrated the upregulation of osteogenic genes, such as TGFB1, MMP8, TUFT1, TFIP11, BMP2, and BMP4, in the presence of PEI-EVs. Upregulation of BMP2/4 was confirmed for Evo enriched with PEI-EVs and hPDLSCs both in vitro by Western blot and in vivo by immunofluorescence.

Conclusion

Our results indicated that Evo enriched with hPDLSCs and PEI-EVs is able to promote a bone-regeneration process for the treatment of calvarium and ossification defects caused by accidental or surgery trauma. In particular, PEI-EVs had a significant role in activation of the osteogenic process.

Extracellular vesicles in cartilage homeostasis and osteoarthritis

PURPOSE OF REVIEW

Extracellular vesicles carry bioactive molecules that can be transferred between cells and tissues. The purpose of this review is to describe how extracellular vesicles regulate functions of cells in cartilage and other joint tissues. The potential application of extracellular vesicles in the treatment of osteoarthritis and as biomarkers will also be discussed.

RECENT FINDINGS

Extracellular vesicles are found in synovial fluid, in articular cartilage and in the supernatants of synoviocytes and chondrocytes. Extracellular vesicles in cartilage have been proposed to be involved in cross talk between cells in joint tissues and to affect extracellular matrix turnover and inflammation. Extracellular vesicles from arthritic joints can promote abnormal gene expression and changes in cartilage extracellular matrix, including abnormal mineralization. Promising results were obtained in the therapeutic application of mesenchymal stem cell-derived extracellular vesicles for cartilage repair and experimental osteoarthritis.

SUMMARY

Extracellular vesicles have emerged as vehicles for the exchange of bioactive signaling molecules within cartilage and between joint tissues to promote joint homeostasis and arthritis pathogenesis. As the molecular content of extracellular vesicles can be customized, they offer utility in therapeutic applications.

Engineered exosomes: A new promise for the management of musculoskeletal diseases

BACKGROUND

Exosomes are nanovesicles actively secreted by potentially all cell types, including tumour cells, with the primary role of extracellular systemic communication mediators, both at autocrine and paracrine levels, at short and long distances. Recently, different studies have used exosomes as a delivery system for a plethora of different molecules, such as drugs, microRNAs and proteins. This has been made possible thanks to the simplicity in exosomes engineering, their great stability and versatility for applications in oncology as well as in regenerative medicine.

SCOPE OF REVIEW

The aim of this review is to provide information on the state-of-the-art and possible applications of engineered exosomes, both for cargo and specific cell-targeting, in different pathologies related to the musculoskeletal system.

MAJOR CONCLUSIONS

The use of exosomes as therapeutic agents is rapidly evolving, different studies explore drug delivery with exosomes using different molecules, showing an enormous potential in various research fields such as oncology and regenerative medicine.

GENERAL SIGNIFICANCE

However, despite the significant progress made by the different studies carried out, currently, the use of exosomes is not a therapeutic reality for the considerable difficulties to overcome.

Vesicle-Mediated Control of Cell Function: The Role of Extracellular Matrix and Microenvironment

Extracellular vesicles (EVs) — including exosomes, microvesicles and apoptotic bodies — have received much scientific attention last decade as mediators of a newly discovered cell-to-cell communication system, acting at short and long distances. EVs carry biologically active molecules, thus providing signals that influence a spectrum of functions in recipient cells during various physiological and pathological processes. Recent findings point to EVs as very attractive immunomodulatory therapeutic agents, vehicles for drug delivery and diagnostic and prognostic biomarkers in liquid biopsies. In addition, EVs interact with and regulate the synthesis of extracellular matrix (ECM) components, which is crucial for organ development and wound healing, as well as bone and cardiovascular calcification. EVs carrying matrix metalloproteinases (MMPs) are involved in ECM remodeling, thus modifying tumor microenvironment and contributing to premetastatic niche formation and angiogenesis. Here we review the role of EVs in control of cell function, with emphasis on their interaction with ECM and microenvironment in health and disease.

Exosomes and regenerative medicine: state of the art and perspectives

Exosomes have attracted the attention of the scientific community in recent years due to their widespread distribution, their possible functions as biomarkers of disease, and their great potential to be applied as therapeutic agents. Exosomes carry proteins and nucleic acids that can facilitate their uptake by distant target cells through endocytosis, such that exosomes could be targeted to a specific cell or cells to enhance or interfere with specific biological processes. This review will mainly focus on their roles in tissue repair and regenerative processes. Exosomal engineering and their potential applications in tissue regeneration are also reviewed here as an outlook for future research.

Lipid, Protein, and MicroRNA Composition Within Mesenchymal Stem Cell-Derived Exosomes

Mesenchymal stem cells (MSCs) were regarded as one of the most promising type of seed cells in tissue engineering due to its easy accessibility and multipotent feature of being able to differentiate into adipocyte, osteoblast, cardiomyocytes, and neurons. For years, MSCs have been applied in treating cardiovascular disease, reconstructing kidney injury, and remodeling immune system with remarkable achievements. Basic researches revealed that its clinic effects are not only due to their pluripotent ability but also through their paracrine function that they synthesize and secrete a broad spectrum of growth factors and cytokines. Recent studies show that exosomes is the main paracrine executor of MSCs. The lipid bilayer of exosome maintains its stability and integrity and keeps biological potency of biological substance within it. MSC-derived exosomes were shown to be successful in treating many diseases, including tumor and cardiovascular diseases. However, the exact composition of MSC-derived exosomes is not known yet. In this review, we will discuss the lipid, protein, and microRNA contents within MSC-derived exosomes based on current studies to guide further research and clinical applications of MSC-derived exosomes.

Exosomes and Stem Cells in Degenerative Disease Diagnosis and Therapy

Stroke can cause death and disability, resulting in a huge burden on society. Parkinson’s disease (PD) is a chronic neurodegenerative disorder characterized by motor dysfunction. Osteoarthritis (OA) is a progressive degenerative joint disease characterized by cartilage destruction and osteophyte formation in the joints. Stem cell therapy may provide a biological treatment alternative to traditional pharmacological therapy. Mesenchymal stem cells (MSCs) are preferred because of their differentiation ability and possible derivation from many adult tissues. In addition, the paracrine effects of MSCs play crucial anti-inflammatory and immunosuppressive roles in immune cells. Extracellular vesicles (EVs) are vital mediators of cell-to-cell communication. Exosomes contain various molecules such as microRNA (miRNA), which mediates biological functions through gene regulation. Therefore, exosomes carrying miRNA or other molecules can enhance the therapeutic effects of MSC transplantation. MSC-derived exosomes have been investigated in various animal models representing stroke, PD, and OA. Exosomes are a subtype of EVs. This review article focuses on the mechanism and therapeutic potential of MSC-derived exosomes in stroke, PD, and OA in basic and clinical aspects.

Stem cell-based therapeutic strategies for cartilage defects and osteoarthritis

The gold standard cell therapy for repair of articular cartilage defects is autologous chondrocyte implantation, with good outcomes long-term. Mesenchymal stromal/stem cells (MSCs) from bone marrow or connective tissues such as fat are being pursued as alternatives for cartilage repair, and are trialled via intra-articular administration in patients with knee osteoarthritis. Early-phase clinical studies concur on safety and provide some promising insight into efficacy, but the mechanism of action remains unclear. Recent studies implicate extracellular vesicles as important mediators of MSC action, offering exciting therapeutic prospects. Our increasing understanding of the mechanisms underlying intrinsic articular cartilage maintenance and repair fosters hope that novel/repurposed therapeutics could elicit repair through activation of endogenous stem/progenitor cells to maintain healthy joints and prevent osteoarthritis.

Harnessing extracellular vesicles to direct endochondral repair of large bone defects

Large bone defects remain a tremendous clinical challenge. There is growing evidence in support of treatment strategies that direct defect repair through an endochondral route, involving a cartilage intermediate. While culture-expanded stem/progenitor cells are being evaluated for this purpose, these cells would compete with endogenous repair cells for limited oxygen and nutrients within ischaemic defects. Alternatively, it may be possible to employ extracellular vesicles (EVs) secreted by culture-expanded cells for overcoming key bottlenecks to endochondral repair, such as defect vascularization, chondrogenesis, and osseous remodelling. While mesenchymal stromal/stem cells are a promising source of therapeutic EVs, other donor cells should also be considered. The efficacy of an EV-based therapeutic will likely depend on the design of companion scaffolds for controlled delivery to specific target cells. Ultimately, the knowledge gained from studies of EVs could one day inform the long-term development of synthetic, engineered nanovesicles. In the meantime, EVs harnessed from in vitro cell culture have near-term promise for use in bone regenerative medicine. This narrative review presents a rationale for using EVs to improve the repair of large bone defects, highlights promising cell sources and likely therapeutic targets for directing repair through an endochondral pathway, and discusses current barriers to clinical translation. Cite this article: E. Ferreira, R. M. Porter. Harnessing extracellular vesicles to direct endochondral repair of large bone defects. Bone Joint Res 2018;7:263-273. DOI: 10.1302/2046-3758.74.BJR-2018-0006.

Dietary exosome-miR-23b may be a novel therapeutic measure for preventing Kashin-Beck disease

Previous studies have identified a close association between diet and the prevalence of Kashin-Beck disease (KBD); however, the mechanisms via which the diet protects against KBD-associated cartilage injury has remained elusive. Recent international research studies have revealed a therapeutic role of dietary exosome micro (mi)RNAs in repairing chondrocyte lesions by regulating genes and proteins associated with cellular apoptosis and extracellular matrix. Vital molecules affecting bio-functions of chondrocytes, including miR-23b and protein kinase cyclic AMP-activated catalytic subunit β, were preliminarily identified to be dysregulated in cells and cartilage tissue of KBD patients. The function of dietary exosome in the repair of chondrocyte lesions in KBD is a novel topic in this field. It is worth exploring the protective role of dietary exosome-miR-23b against chondrocyte damage through the regulation of the protein kinase A (PKA) signaling pathway. The following aims are significant in future studies: i) To verify the association between exosome and cartilage damage in KBD patients; ii) to identify whether the protective mechanism of miR-23b in cartilage damage proceeds through regulating the PKA pathway; and iii) to explore the therapeutic role of dietary exosome-miR-23b in repairing chondrocyte lesions induced by environmental risk factors. These ideas may help establish the therapeutic role and mechanisms of dietary exosome-miR-23b in repairing chondrocyte lesions at the molecular, cellular and organismal level. These studies may simultaneously elucidate the disease pathogenesis and provide evidence for novel biomarkers and therapeutic methods for KBD.

Comparison of Arthroscopic and Conservative Treatments for Knee Osteoarthritis: A 5-Year Retrospective Comparative Study

PURPOSE

To compare the effectiveness of arthroscopic and conservative treatments in patients with knee osteoarthritis (KOA) with 5 years of follow-up.

METHODS

Patients diagnosed with Kellgren-Lawrence grade 2 to 4 KOA who underwent arthroscopic or conservative treatment from May 2005 to May 2012 were included. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score was collected 1, 2, 3, 4, and 5 years after the initial treatment, and the number of patients who underwent total knee arthroplasty (TKA) at every time point was recorded.

RESULTS

Three hundred eighty-two patients (168 in the conservative group and 214 in the arthroscopy group) were included. Five years after the initial treatment, 32 of the 214 patients who underwent arthroscopy (15.0%) compared with 30 of the 168 patients in the conservative treatment group (17.9%) ultimately underwent TKA, with no statistically significant difference between groups (P = .20). The WOMAC score was significantly lower in the arthroscopy group than in the conservative group at year 1 (24.33 ± 21.56 vs 36.43 ± 16.22, respectively) and year 2 (26.31 ± 17.84 vs 35.41 ± 19.21, respectively). There were no significant between-group differences at years 3, 4, and 5.

CONCLUSIONS

Compared with conservative treatment, arthroscopy provided no benefit in decreasing or delaying arthroplasty surgery. However, arthroscopy had a greater ability to relieve symptoms at 1 and 2 years. Our results suggest that arthroscopy can relieve symptoms up to 2 years without elevating the risk of arthroplasty.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Extracellular vesicles: A new therapeutic strategy for joint conditions

Extracellular vesicles (EVs) are attracting increasing interest since they might represent a more convenient therapeutic tool with respect to their cells of origin. In the last years much time and effort have been expended to determine the biological properties of EVs from mesenchymal stem cells (MSCs) and other sources. The immunoregulatory, anti-inflammatory and regenerative properties of MSC EVs have been demonstrated in in vitro studies and animal models of rheumatoid arthritis or osteoarthritis. This cell-free approach has been proposed as a possible better alternative to MSC therapy in autoimmune conditions and tissue regeneration. In addition, EVs show great potential as biomarkers of disease or delivery systems for active molecules. The standardization of isolation and characterization methods is a key step for the development of EV research. A better understanding of EV mechanisms of action and efficacy is required to establish the potential therapeutic applications of this new approach in joint conditions.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

Gene therapy for chondral and osteochondral regeneration: is the future now?

Gene therapy might represent a promising strategy for chondral and osteochondral defects repair by balancing the management of temporary joint mechanical incompetence with altered metabolic and inflammatory homeostasis. This review analysed preclinical and clinical studies on gene therapy for the repair of articular cartilage defects performed over the last 10 years, focussing on expression vectors (non-viral and viral), type of genes delivered and gene therapy procedures (direct or indirect). Plasmids (non-viral expression vectors) and adenovirus (viral vectors) were the most employed vectors in preclinical studies. Genes delivered encoded mainly for growth factors, followed by transcription factors, anti-inflammatory cytokines and, less frequently, by cell signalling proteins, matrix proteins and receptors. Direct injection of the expression vector was used less than indirect injection of cells, with or without scaffolds, transduced with genes of interest and then implanted into the lesion site. Clinical trials (phases I, II or III) on safety, biological activity, efficacy, toxicity or bio-distribution employed adenovirus viral vectors to deliver growth factors or anti-inflammatory cytokines, for the treatment of osteoarthritis or degenerative arthritis, and tumour necrosis factor receptor or interferon for the treatment of inflammatory arthritis.

Exosomes in Extracellular Matrix Bone Biology

PURPOSE OF REVIEW

Exosomes are membrane vesicles that are released by most cell types into the extracellular environment. The purpose of this article is to discuss the main morphological features and contents of bone-derived exosomes, as well as their major isolation and physical characterization techniques. Furthermore, we present various scenarios and discuss potential clinical applications of bone-derived exosomes in bone repair and regeneration.

RECENT FINDINGS

Exosomes were believed to be nanosized vesicles derived from the multivesicular body. Reports now suggest that nanovesicles could bud directly from the plasma membrane. However, the exosome cargo is cell-type specific and is derived from the parent cell. In the bone matrix, several intracellular proteins lacking a signal peptide are transported to the ECM by exosomes. Besides proteins, several mRNA, miRNA, and lipids are exported to the ECM by bone cells and bone marrow stromal cells. Recent evidence suggests that several of the functional components in the cargo could regulate processes of bone formation, inhibit osteoclast activity, and promote fracture repair. Exosomes are powerful cellular molecular machines produced without human intervention and packaged with physiological cargo that could be utilized for molecular therapy in several skeletal disorders such as osteoporosis, osteogenesis imperfecta, and fracture healing. Although much work has been done, there is a lot of information that is still unknown, as exosomes contain a multitude of molecules whose identity and function have yet to be identified.

Adipose mesenchymal stem cells-derived exosomes attenuate retina degeneration of streptozotocin-induced diabetes in rabbits

This study aimed to evaluate the effect of mesenchymal stem cells (MSCs)-derived exosomes in retina regeneration of experimentally induced diabetes mellitus (DM) in a rabbit model. Exosomes are extracellular vesicles that contain many microRNAs (micRNAs), mRNAs, and proteins from their cells of origin. DM was induced by intravenous (IV) injection of streptozotocin in rabbits. MSCs were isolated from adipose tissue of rabbits. Exosomes were extracted from MSCs by ultracentrifugation. Exosomes were injected by different routes (IV, subconjunctival (SC), and intraocular (IO)). Evaluation of the treatment was carried out by histopathological examination of retinal tissues and assessment of micRNA-222 expression level in retinal tissue by real-time polymerase chain reaction. Histologically, by 12 weeks following SC exosomal treatment, the cellular components of the retina were organized in well-defined layers, while IO exosomal injection showed well-defined retinal layers which were obviously similar to layers of the normal retina. However, the retina appeared after IV exosomal injection as irregular ganglionic layer with increased thickness. MicRNA-222 expression level was significantly reduced in diabetic controls when compared to each of healthy controls and other diabetic groups with IV, SC, and IO routes of injected exosomes (0.06 ± 0.02 vs. 0.51 ± 0.07, 0.28 ± 0.08, 0.48 ± 0.06, and 0.42 ± 0.11, respectively). We detected a significant negative correlation between serum glucose and retinal tissue micRNA-222 expression level (r = -0.749, p = 0.001). We can associate the increased expression of micRNA-222 with regenerative changes of retina following administration of MSCs-derived exosomes. The study demonstrates the potency of rabbit adipose tissue-derived MSCs exosomes in retinal repair. So, exosomes are considered as novel therapeutic vectors in MSCs-based therapy through its role in shuttling of many factors including micRNA-222.