Enhanced proangiogenic potential of mesenchymal stem cell-derived exosomes stimulated by a nitric oxide releasing polymer

Nitric Oxide-Releasing Platforms for Treating Cardiovascular Disease

Cardiovascular disease (CVD) is the first leading cause of death globally. Nitric oxide (NO) is an important signaling molecule that mediates diverse processes in the cardiovascular system, thereby providing a fundamental basis for NO-based therapy of CVD. At present, numerous prodrugs have been developed to release NO in vivo. However, the clinical application of these prodrugs still faces many problems, including the low payloads, burst release, and non-controlled delivery. To address these, various biomaterial-based platforms have been developed as the carriers to deliver NO to the targeted tissues in a controlled and sustained manner. This review aims to summarize recent developments of various therapeutic platforms, engineered to release NO for the treatment of CVD. In addition, two potential strategies to improve the effectiveness of existing NO therapy are also discussed, including the combination of NO-releasing platforms and either hydrogen sulfide-based therapy or stem cell therapy. Hopefully, some NO-releasing platforms may provide important therapeutic benefits for CVD.

Xenogenic Neural Stem Cell-Derived Extracellular Nanovesicles Modulate Human Mesenchymal Stem Cell Fate and Reconstruct Metabolomic Structure

Extracellular nanovesicles, particularly exosomes, can deliver their diverse bioactive biomolecular content, including miRNAs, proteins, and lipids, thus providing a context for investigating the capability of exosomes to induce stem cells toward lineage-specific cells and tissue regeneration. In this study, it is demonstrated that rat subventricular zone neural stem cell-derived exosomes (rSVZ-NSCExo) can control neural-lineage specification of human mesenchymal stem cells (hMSCs). Microarray analysis shows that the miRNA content of rSVZ-NSCExo is a faithful representation of rSVZ tissue. Through immunocytochemistry, gene expression, and multi-omics analyses, the capability to use rSVZ-NSCExo to induce hMSCs into a neuroglial or neural stem cell phenotype and genotype in a temporal and dose-dependent manner via multiple signaling pathways is demonstrated. The current study presents a new and innovative strategy to modulate hMSCs fate by harnessing the molecular content of exosomes, thus suggesting future opportunities for rSVZ-NSCExo in nerve tissue regeneration.

Nitric oxide-releasing biomaterials for promoting wound healing in impaired diabetic wounds: State of the art and recent trends

Impaired diabetic wounds are serious pathophysiological complications associated with persistent microbial infections including failure in the closure of wounds, and the cause of a high frequency of lower limb amputations. The healing of diabetic wounds is attenuated due to the lack of secretion of growth factors, prolonged inflammation, and/or inhibition of angiogenic activity. Diabetic wound healing can be enhanced by supplying nitric oxide (NO) endogenously or exogenously. NO produced inside the cells by endothelial nitric oxide synthase (eNOS) naturally aids wound healing through its beneficial vasculogenic effects. However, during hyperglycemia, the activity of eNOS is affected, and thus there becomes an utmost need for the topical supply of NO from exogenous sources. Thus, NO-donors that can release NO are loaded into wound healing patches or wound coverage matrices to treat diabetic wounds. The burst release of NO from its donors is prevented by encapsulating them in polymeric hydrogels or nanoparticles for supplying NO for an extended duration of time to the diabetic wounds. In this article, we review the etiology of diabetic wounds, wound healing strategies, and the role of NO in the wound healing process. We further discuss the challenges faced in translating NO-donors as a clinically viable nanomedicine strategy for the treatment of diabetic wounds with a focus on the use of biomaterials for the encapsulation and in vivo controlled delivery of NO-donors.

Nanostructured particles assembled from natural building blocks for advanced therapies

Advanced treatments based on immune system manipulation, gene transcription and regulation, specific organ and cell targeting, and/or photon energy conversion have emerged as promising therapeutic strategies against a range of challenging diseases. Naturally derived macromolecules (e.g., proteins, lipids, polysaccharides, and polyphenols) have increasingly found use as fundamental building blocks for nanostructured particles as their advantageous properties, including biocompatibility, biodegradability, inherent bioactivity, and diverse chemical properties make them suitable for advanced therapeutic applications. This review provides a timely and comprehensive summary of the use of a broad range of natural building blocks in the rapidly developing field of advanced therapeutics with insights specific to nanostructured particles. We focus on an up-to-date overview of the assembly of nanostructured particles using natural building blocks and summarize their key scientific and preclinical milestones for advanced therapies, including adoptive cell therapy, immunotherapy, gene therapy, active targeted drug delivery, photoacoustic therapy and imaging, photothermal therapy, and combinational therapy. A cross-comparison of the advantages and disadvantages of different natural building blocks are highlighted to elucidate the key design principles for such bio-derived nanoparticles toward improving their performance and adoption. Current challenges and future research directions are also discussed, which will accelerate our understanding of designing, engineering, and applying nanostructured particles for advanced therapies.

Mesenchymal stem cell-derived extracellular vesicles for cell-free therapy of ocular diseases

Mesenchymal stem cells-derived extracellular vesicles (MSC-EVs) have noticeably attracted clinicians' attention in treating ocular diseases. As the paracrine factor of MSCs and an alternative for cell-free therapies, MSC-EVs can be conveniently dropped over the ocular surface or diffused through the retina upon intravitreal injection, without increasing the risks of cellular rejection and tumor formation. For clinical translation, a standardized and scalable production, as well as reprogramming the MSC-EVs, are highly encouraged. This review aims to assess the potential approaches for EV production and functional modification, in addition to summarizing the worldwide clinical trials initiated for various physiological systems and the specific biochemical effects of MSC-EVs on the therapy of eye diseases. Recent advances in the therapy of ocular diseases based on MSC-EVs are reviewed, and the associated challenges and prospects are discussed as well.

MSC-derived sEV-loaded hyaluronan hydrogel promotes scarless skin healing by immunomodulation in a large skin wound model

Designing hydrogel-based constructs capable of adjusting immune cell functions holds promise for skin tissue regeneration. Mesenchymal stem cell (MSC)-derived small extracellular vesicles (sEVs) have attracted increasing attention owing to their anti-inflammatory and proangiogenic effects. Herein, we constructed a biofunctional hydrogel in which MSC-derived sEVs were incorporated into the injectable hyaluronic acid (HA) hydrogel, thus endowing the hydrogel with immunomodulatory effects. When implanted onto the wound site in a mouse large skin injury model, this functional hydrogel facilitates wound healing and inhibits scar tissue formation by driving macrophages towards an anti-inflammatory and anti-fibrotic (M2c) phenotype. Further investigation showed that the M2c-like phenotype induced by MSC-derived sEVs markedly inhibited the activation of fibroblasts, which could result in scarless skin wound healing. Taken together, these results suggest that modulation of the immune response is a promising and efficient approach to prevent fibrotic scar formation.

Delivery of VEGF and delta-like 4 to synergistically regenerate capillaries and arterioles in ischemic limbs

Vascularization of the poorly vascularized limbs affected by critical limb ischemia (CLI) is necessary to salvage the limbs and avoid amputation. Effective vascularization requires forming not only capillaries, but also arterioles and vessel branching. These processes rely on the survival, migration and morphogenesis of endothelial cells in the ischemic limbs. Yet endothelial cell functions are impaired by the upregulated TGFβ. Herein, we developed an injectable hydrogel-based drug release system capable of delivering both VEGF and Dll4 to synergistically restore endothelial cellular functions, leading to accelerated formation of capillaries, arterioles and vessel branching. In vitro, the Dll4 and VEGF synergistically promoted the human arterial endothelial cell (HAEC) survival, migration, and formation of filopodial structure, lumens, and branches under the elevated TGFβ1 condition mimicking that of the ischemic limbs. The synergistic effect was resulted from activating VEGFR2, Notch-1 and Erk1/2 signaling pathways. After delivering the Dll4 and VEGF via an injectable and thermosensitive hydrogel to the ischemic mouse hindlimbs, 95% of blood perfusion was restored at day 14, significantly higher than delivery of Dll4 or VEGF only. The released Dll4 and VEGF significantly increased density of capillaries and arterioles, vessel branching point density, and proliferating cell density. Besides, the delivery of Dll4 and VEGF stimulated skeletal muscle regeneration and improved muscle function. Overall, the developed hydrogel-based Dll4 and VEGF delivery system promoted ischemic limb vascularization and muscle regeneration. STATEMENT OF SIGNIFICANCE: Effective vascularization of the poorly vascularized limbs affected by critical limb ischemia (CLI) requires forming not only capillaries, but also arterioles and vessel branching. These processes rely on the survival, migration and morphogenesis of endothelial cells. Yet endothelial cell functions are impaired by the upregulated TGFβ in the ischemic limbs. Herein, we developed an injectable hydrogel-based drug release system capable of delivering both VEGF and Dll4 to synergistically restore endothelial cell functions, leading to accelerated formation of capillaries, arterioles and vessel branching.

Intravenous infusion of the exosomes derived from human umbilical cord mesenchymal stem cells enhance neurological recovery after traumatic brain injury via suppressing the NF-κB pathway

Traumatic brain injury (TBI) is a predominant cause of death and permanent disability globally. In recent years, much emphasis has been laid on treatments for TBI. Increasing evidence suggests that human umbilical cord mesenchymal stem cells (HUCMSCs) can improve neurological repair after TBI. However, the clinical use of HUCMSCs transplantation in TBI has been limited by immunological rejection, ethical issues, and the risk of tumorigenicity. Many studies have shown that HUCMSCs-derived exosomes may be an alternative approach for HUCMSCs transplantation. We hypothesized that exosomes derived from HUCMSCs could inhibit apoptosis after TBI, reduce neuroinflammation, and promote neurogenesis. A rat model of TBI was established to investigate the efficiency of neurological recovery with exosome therapy. We found that exosomes derived from HUCMSCs significantly ameliorated sensorimotor function and spatial learning in rats after TBI. Moreover, HUCMSCs-derived exosomes significantly reduced proinflammatory cytokine expression by suppressing the NF-κB signaling pathway. Furthermore, we found that HUCMSC-derived exosomes inhibited neuronal apoptosis, reduced inflammation, and promoted neuron regeneration in the injured cortex of rats after TBI. These results indicate that HUCMSCs-derived exosomes may be a promising therapeutic strategy for TBI.

Engineering stem cells to produce exosomes with enhanced bone regeneration effects: an alternative strategy for gene therapy

BACKGROUND

Exosomes derived from stem cells have been widely studied for promoting regeneration and reconstruction of multiple tissues as "cell-free" therapies. However, the applications of exosomes have been hindered by limited sources and insufficient therapeutic potency.

RESULTS

In this study, a stem cell-mediated gene therapy strategy is developed in which mediator mesenchymal stem cells are genetically engineered by bone morphogenetic protein-2 gene to produce exosomes (MSC-BMP2-Exo) with enhanced bone regeneration potency. This effect is attributed to the synergistic effect of the content derived from MSCs and the up-regulated BMP2 gene expression. The MSC-BMP2-Exo also present homing ability to the injured site. The toxic effect of genetical transfection vehicles is borne by mediator MSCs, while the produced exosomes exhibit excellent biocompatibility. In addition, by plasmid tracking, it is interesting to find a portion of plasmid DNA can be encapsulated by exosomes and delivered to recipient cells.

CONCLUSIONS

In this strategy, engineered MSCs function as cellular factories, which effectively produce exosomes with designed and enhanced therapeutic effects. The accelerating effect in bone healing and the good biocompatibility suggest the potential clinical application of this strategy.

Hydrogel Loaded with VEGF/TFEB-Engineered Extracellular Vesicles for Rescuing Critical Limb Ischemia by a Dual-Pathway Activation Strategy

Critical limb ischemia (CLI) is the most severe clinical manifestation of peripheral arterial disease, which causes many amputations and deaths. Conventional treatment strategies for CLI (e.g., stent implantation and vascular surgery) bring surgical risk, which are not suitable for each patient. Extracellular vesicles (EVs) can be a potential solution for CLI. Herein, vascular endothelial growth factor (VEGF; i.e., a crucial molecule related to angiogenesis) and transcription factor EB (TFEB; i.e., a pivotal regulator of autophagy) are chosen as the target gene to improve the bioactivity of EVs derived from endothelial cells. The VEGF/TFEB-engineered EVs (Engineered-EVs) are fabricated by genetically engineering the parent cells, and their versatile functions are confirmed using three cell models (human umbilical vein endothelial cells, myoblast, and monocytes). Injectable thermal-responsive hydrogel are then combined with Engineered-EVs to combat CLI. These results reveal that the hydrogel can enhance the stability of Engineered-EVs in vivo and release EVs at different temperatures. Moreover, the results of animal studies indicate that Engineered-EV/Hydrogel can significantly improve neovascularization, attenuate muscle injury, and recover limb function after CLI. Finally, mechanistic studies shed light on the therapeutic effect of Engineered-EV/Hydrogel due to the activated VEGF/VEGFR pathway and autophagy-lysosomal pathway.

The sustained PGE2 release matrix improves neovascularization and skeletal muscle regeneration in a hindlimb ischemia model

BACKGROUND

The promising therapeutic strategy for the treatment of peripheral artery disease (PAD) is to restore blood supply and promote regeneration of skeletal muscle regeneration. Increasing evidence revealed that prostaglandin E₂ (PGE₂), a lipid signaling molecule, has significant therapeutic potential for tissue repair and regeneration. Though PGE₂ has been well reported in tissue regeneration, the application of PGE₂ is hampered by its short half-life in vivo and the lack of a viable system for sustained release of PGE₂.

RESULTS

In this study, we designed and synthesized a new PGE₂ release matrix by chemically bonding PGE₂ to collagen. Our results revealed that the PGE₂ matrix effectively extends the half-life of PGE₂ in vitro and in vivo. Moreover, the PGE₂ matrix markedly improved neovascularization by increasing angiogenesis, as confirmed by bioluminescence imaging (BLI). Furthermore, the PGE₂ matrix exhibits superior therapeutic efficacy in the hindlimb ischemia model through the activation of MyoD1-mediated muscle stem cells, which is consistent with accelerated structural recovery of skeletal muscle, as evidenced by histological analysis.

CONCLUSIONS

Our findings highlight the chemical bonding strategy of chemical bonding PGE₂ to collagen for sustained release and may facilitate the development of PGE₂-based therapies to significantly improve tissue regeneration.

Osteostatin improves the Osteogenic differentiation of mesenchymal stem cells and enhances angiogenesis through HIF-1α under hypoxia conditions in vitro

BACKGROUND

Hypoxia conditions induced by bone defects would prolong the duration of bone regeneration. The effect of osteostatin (OST) on the osteogenic differentiation of mesenchymal stem cells (MSCs) and angiogenesis under hypoxia conditions remain unexplored.

METHODS

SPF mice were obtained, and MSCs were isolated from bone marrow. MSCs were treated with 1% oxygen for hypoxia induction, and 200 nM of OST was used to treat cells under nomorxia or hypoxia conditions. Cell proliferation was evaluated using CCK8 assay, and trypan blue staining was implemented for determining cell death ratio. Alkaline phosphatase activity and alizarin redS staining was conducted to histologically evaluated osteogenic differentiation. Flow cytometry was used for the detection of CD31^hiEmcn^hi cells (Type H ECs), whose migration was detected by Transwell assay and angiogenesis was measured by tube formation assay. Protein level was measured by western blotting and mRNA level was monitored via RT-qPCR.

RESULTS

The MSC proliferation was enhanced by OST under hypoxia conditions. The osteogenic differentiation of MSCs was decreased under hypoxia conditions, and treatment of OST significantly reversed its inhibitory effect. The hypoxia treated culture medium of MSCs promoted the proliferation, migration, and angiogenesis of type H ECs, while the effects were further strengthened by OST addition. HIF-1α was found to be upregulated in hypoxia treated MSCs, whereas silencing of HIF-1α had reversed effects on the angiogenic capacity of Type H ECs.

CONCLUSION

OST improved the proliferation and osteogenic differentiation of MSCs and further promoted angiogenesis of type H ECs through upregulating HIF-1α expression.

A study of lovastatin and L-arginine co-loaded PLGA nanomedicine for enhancing nitric oxide production and eNOS expression

Nitric oxide (NO) is an exceptional endogenous biological gas that mediates and regulates physiological and pathological processes in the human body. However, its synthesis process is impaired during athero-progression and formation. Hence, a strategy to boost NO production and target endothelial nitric oxide synthase (eNOS) is crucial and intriguing in atherosclerosis (AS) management. Herein, we prepare L-arginine (LA) and lovastatin (LV) co-loaded PLGA nanomedicine to achieve sustainable release for enhancing NO production. The utilization of LA reveals that LA has dual contributions, acting as a NO donor and enhancing the solubility of LV by stabilizing PLGA NPs. PLGA-LA/LV demonstrated its potential to boost NO in vitro and in vivo confirmed using DAF-FM DA, augment eNOS and p-eNOS mRNA and protein levels, and suppress the ki67 proliferation marker in VSMCs; in addition, it lowers the total cholesterol level of blood plasma in C57BL/6 mice. Moreover, PLGA can protect the compound delivered and enhance the bioavailability to reach and get released in the blood circulation after oral administration. Collectively, our results endow a safe and efficient nanomedicine outcome, specifically with potential for AS management.

Therapeutic implications of exosomes in the treatment of radiation injury

Radiotherapy is one of the main cancer treatments, but it may damage normal tissue and cause various side effects. At present, radioprotective agents used in clinics have side effects such as nausea, vomiting, diarrhea and hypotension, which limit their clinical application. It has been found that exosomes play an indispensable role in radiation injury. Exosomes are lipid bilayer vesicles that carry various bioactive substances, such as proteins, lipids and microRNA (miRNA), that play a key role in cell-to-cell communication and affect tissue injury and repair. In addition, studies have shown that radiation can increase the uptake of exosomes in cells and affect the composition and secretion of exosomes. Here, we review the existing studies and discuss the effects of radiation on exosomes and the role of exosomes in radiation injury, aiming to provide new insights for the treatment of radiation injury.

Molecular Imaging of Tumor Progression and Angiogenesis by Dual Bioluminescence

Angiogenesis is a prerequisite for tumor growth and invasion, and anti-angiogenesis has become a highlight in tumor treatment research. However, so far, there is no reliable solution for how to simultaneously visualize the relationship between tumor progression and angiogenesis. Bioluminescence imaging (BLI) has been broadly utilized and is a very promising non-invasive imaging technique with the advantages of low cost, high sensitivity, and robust specificity. In this chapter, we describe a dual bioluminescence imaging BLI protocol for tumor progression and angiogenesis through implanting murine breast cancer cell line 4T1 which stably expressing Renilla luciferase (RLuc) into the transgenic mice with angiogenesis-induced firefly luciferase (FLuc) expression. This modality enables us to synchronously monitor the tumor progression and angiogenesis in the same mouse, which has broad applicability in oncology studies.

Recent strategies for improving hemocompatibility and endothelialization of cardiovascular devices and inhibition of intimal hyperplasia

Cardiovascular diseases have become one of the leading causes of mortality worldwide. Stents and artificial grafts have been used to treat cardiovascular diseases. Thrombosis and restenosis seriously impact clinical outcome...

The Potential Therapeutic Role of Mesenchymal Stem Cells-Derived Exosomes in Osteoradionecrosis

As one of the most serious complications of radiotherapy, osteoradionecrosis (ORN) seriously affects the quality of life of patients and even leads to death. Vascular injury and immune disorders are the main causes of bone lesions. The traditional conservative treatment of ORN has a low cure rate and high recurrent. Exosomes are a type of extracellular bilayer lipid vesicles secreted by almost all cell types. It contains cytokines, proteins, mRNA, miRNA, and other bioactive cargos, which contribute to several distinct processes. The favorable biological functions of mesenchymal stem cells-derived exosomes (MSC exosomes) include angiogenesis, immunomodulation, bone regeneration, and ferroptosis regulation. Exploring the characteristic of ORN and MSC exosomes can promote bone regeneration therapies. In this review, we summarized the current knowledge of ORN and MSC exosomes and highlighted the potential application of MSC exosomes in ORN treatment.

A functional extracellular matrix biomaterial enriched with VEGFA and bFGF as vehicle of human umbilical cord mesenchymal stem cells in skin wound healing

The construction of microvascular network is one of the greatest challenges for tissue engineering and cell therapy. Endothelial cells are essential for the construction of network of blood vessels. However, their application meets challenges in clinic due to the limited resource of autologous endothelium. Mesenchymal stem cells can effectively promote the angiogenesis in ischemic tissues for their abilities of endothelial differentiation and paracrine, and abundant sources. Extracellular matrix (ECM) has been widely used as an ideal biomaterial to mimic cellular microenvironment for tissue engineering due to its merits of neutrality, good biocompatibility, degradability, and controllability. In this study, a functional cell derived ECM biomaterial enriched with VEGFA and bFGF by expressing the collagen-binding domain fused factor genes in host cells was prepared. This material could induce endothelial differentiation of human umbilical cord mesenchymal stem cells (hUCMSCs) and promote angiogenesis, which may improve the healing effect of skin injury. Our research not only provides a functional ECM material to inducing angiogenesis by inducing endothelial differentiation of hUCMSCs, but also shed light on the ubiquitous approaches to endow ECM materials different functions by enriching different factors. This study will benefit tissue engineering and regenerative medicine researches.

Constructing a cell microenvironment with biomaterial scaffolds for stem cell therapy

Stem cell therapy is widely recognized as a promising strategy for exerting therapeutic effects after injury in degenerative diseases. However, limitations such as low cell retention and survival rates after transplantation exist in clinical applications. In recent years, emerging biomaterials that provide a supportable cellular microenvironment for transplanted cells have optimized the therapeutic efficacy of stem cells in injured tissues or organs. Advances in the engineered microenvironment are revolutionizing our understanding of stem cell-based therapies by co-transplanting with synthetic and tissue-derived biomaterials, which offer a scaffold for stem cells and propose an unprecedented opportunity to further employ significant influences in tissue repair and regeneration.

Mussel-inspired functionalization of electrospun scaffolds with polydopamine-assisted immobilization of mesenchymal stem cells-derived small extracellular vesicles for enhanced bone regeneration

Mesenchymal stem cells-derived small extracellular vesicles (MSCs-sEV) have shown promising prospects as a cell-free strategy for bone tissue regeneration. Here, a bioactive MSCs-sEV-loaded electrospun silk fibroin/poly(ε-caprolactone) (SF/PCL) scaffold was synthesized via a mussel-inspired immobilization strategy assisted by polydopamine (pDA). This pDA modification endowed the as-prepared scaffold with high loading efficiency and sustained release profile of sEV. In addition, the fabricated composite scaffold exhibited good physiochemical, mechanical, and biocompatible properties. In vitro cellular experiments indicated that the MSCs-sEV-loaded composite scaffold promoted the adhesion and spreading of preosteoblast and endothelial cells, as well as enhanced osteogenic differentiation and angiogenic activity. In vivo experiments showed that the functionalized electrospun scaffolds promoted bone regeneration in a rat calvarial bone defect model. Results suggest that the developed MSCs-sEV-anchored pDA-modified SF/PCL electrospun scaffolds possess high application potential in bone tissue engineering owing to their powerful pro-angiogenic and -osteogenic capacities, cell-free bioactivity, and cost effectiveness.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Attenuate Radiation-Induced Lung Injury via miRNA-214-3p

Aims: Radiotherapy is an effective treatment for thoracic malignancies, but it can cause pulmonary injury and may lead to respiratory failure in a subset of patients. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) are now recognized as a new candidate for cell-free treatment of lung diseases. Here, we investigated whether MSC-derived EVs (MSC-EVs) could ameliorate radiation-induced lung injury. Results: We exposed mice to thoracic radiation with a total dose of 15 Gy and assessed the protective effects of MSC-EVs on endothelial cells damage, vascular permeability, inflammation, and fibrosis. We found that MSC-EVs attenuated radiation-induced lung vascular damage, inflammation, and fibrosis. Moreover, MSC-EVs reduced the levels of radiation-induced DNA damage by downregulating ATM/P53/P21 signaling. Our results confirmed that the downregulation of ataxia telangiectasia mutated (ATM) was regulated by miR-214-3p, which was enriched in MSC-EVs. Further analysis demonstrated that MSC-EVs inhibited the senescence-associated secretory phenotype development and attenuated the radiation-induced injury of endothelial cells. Innovation and Conclusion: Our study reveals that MSC-EVs can reduce pulmonary radiation injury through transferring miR-214-3p, providing new avenues to minimize lung injury from radiation therapy. Antioxid. Redox Signal. 35, 849-862.

Treatment with adipose-derived regenerative cells enhances ischemia-induced angiogenesis via exosomal microRNA delivery in mice

Adipose-derived regenerative cells (ADRCs), mesenchymal stem/progenitor cells from subcutaneous adipose tissue, have been shown to stimulate angiogenesis in hind limb ischemia, an effect attributed to paracrine action on endothelial cells (ECs) in mice. Despite promising therapeutic effects, the relevant molecules promoting neovascularization in this setting have not been fully elucidated. Extracellular vesicles, crucial mediators of intercellular communication, are recognized as a new therapeutic modality for regenerative medicine. Here, we found that GW4869, an exosome biogenesis inhibitor targeting neutral sphingomyelinase, impaired ADRCs-mediated angiogenesis and improvement of blood perfusion in a murine hind limb ischemia model. In addition, while the supernatant of ADRCs induced murine EC migration, this effect was attenuated by pre-treatment with GW4869. RNA analysis revealed that treatment of ADRCs with GW4869 reduced the expression of microRNA-21 (miR-21), miR-27b, miR-322, and let-7i in ADRCs-derived exosomes. Furthermore, the exosomes derived from GW4869-treated ADRCs induced the expression of the miR-21 targets Smad7 and Pten, and the miR-322 target Cul2, in ECs. These findings suggest that several miRNAs in ADRCs-derived exosomes contribute to angiogenesis and improvement of blood perfusion in a murine hind limb ischemia model.

Exosomal microRNAs from mesenchymal stem/stromal cells: Biology and applications in neuroprotection

Mesenchymal stem/stromal cells (MSCs) are extensively studied as cell-therapy agents for neurological diseases. Recent studies consider exosomes secreted by MSCs as important mediators for MSCs’ neuroprotective functions. Exosomes transfer functional molecules including proteins, lipids, metabolites, DNAs, and coding and non-coding RNAs from MSCs to their target cells. Emerging evidence shows that exosomal microRNAs (miRNAs) play a key role in the neuroprotective properties of these exosomes by targeting several genes and regulating various biological processes. Multiple exosomal miRNAs have been identified to have neuroprotective effects by promoting neurogenesis, neurite remodeling and survival, and neuroplasticity. Thus, exosomal miRNAs have significant therapeutic potential for neurological disorders such as stroke, traumatic brain injury, and neuroinflammatory or neurodegenerative diseases and disorders. This review discusses the neuroprotective effects of selected miRNAs (miR-21, miR-17-92, miR-133, miR-138, miR-124, miR-30, miR146a, and miR-29b) and explores their mechanisms of action and applications for the treatment of various neurological disease and disorders. It also provides an overview of state-of-the-art bioengineering approaches for isolating exosomes, optimizing their yield and manipulating the miRNA content of their cargo to improve their therapeutic potential.

Impact of exosome-mediated feto-maternal interactions on pregnancy maintenance and development of obstetric complications

Pregnancy is an immunological paradox, a phenomenon in which the foetus and the placenta, containing foreign antigens to the mother, develop without inducing rejection by the maternal immune system. Cell-to-cell communication between the foetus and the mother is mediated by secreted factors such as cytokines, hormones and extracellular vesicles (EVs) for a successful pregnancy and to avoid rejection. Exosomes, the smallest of EVs, are released extracellularly, where they are taken up by proximal or distant recipient cells. Here, we discuss the role of EVs, especially exosomes in feto-maternal communication during pregnancy. This review will provide an overview of the functional roles exosomes may play during embryo implantation, modulating immune responses during pregnancy and the onset of labour. Moreover, we will discuss exosomal function in obstetric pathology, and the development of pregnancy-associated complications such as preeclampsia and preterm birth as well as the biomarker potential of exosomes for detecting such conditions.

The Emerging Role of Exosomes in the Treatment of Human Disorders With a Special Focus on Mesenchymal Stem Cells-Derived Exosomes

Extracellular vesicles (EVs) are produced by diverse eukaryotic and prokaryotic cells. They have prominent roles in the modulation of cell-cell communication, inflammation versus immunomodulation, carcinogenic processes, cell proliferation and differentiation, and tissue regeneration. These acellular vesicles are more promising than cellular methods because of the lower risk of tumor formation, autoimmune responses and toxic effects compared with cell therapy. Moreover, the small size and lower complexity of these vesicles compared with cells have made their production and storage easier than cellular methods. Exosomes originated from mesenchymal stem cells has also been introduced as therapeutic option for a number of human diseases. The current review aims at summarization of the role of EVs in the regenerative medicine with a focus on their therapeutic impacts in liver fibrosis, lung disorders, osteoarthritis, colitis, myocardial injury, spinal cord injury and retinal injury.

Therapeutic Potential of Extracellular Vesicles for Sepsis Treatment

Sepsis is a deadly condition lacking a specific treatment despite decades of research. This has prompted the exploration of new approaches, with extracellular vesicles (EVs) emerging as a focal area. EVs are nanosized, cell-derived particles that transport bioactive components (i.e., proteins, DNA, and RNA) between cells, enabling both normal physiological functions and disease progression depending on context. In particular, EVs have been identified as critical mediators of sepsis pathophysiology. However, EVs are also thought to constitute the biologically active component of cell-based therapies and have demonstrated anti-inflammatory, anti-apoptotic, and immunomodulatory effects in sepsis models. The dual nature of EVs in sepsis is explored here, discussing their endogenous roles and highlighting their therapeutic properties and potential. Related to the latter component, prior studies involving EVs from mesenchymal stem/stromal cells (MSCs) and other sources are discussed and emerging producer cells that could play important roles in future EV-based sepsis therapies are identified. Further, how methodologies could impact therapeutic development toward sepsis treatment to enhance and control EV potency is described.

Mesenchymal stromal cell-derived exosomes in cardiac regeneration and repair

Mesenchymal stromal cell (MSC)-derived exosomes play a promising role in regenerative medicine. Their trophic and immunomodulatory potential has made them a promising candidate for cardiac regeneration and repair. Numerous studies have demonstrated that MSC-derived exosomes can replicate the anti-inflammatory, anti-apoptotic, and pro-angiogenic and anti-fibrotic effects of their parent cells and are considered a substitute for cell-based therapies. In addition, their lower tumorigenic risk, superior immune tolerance, and superior stability compared with their parent stem cells make them an attractive option in regenerative medicine. The therapeutic effects of MSC-derived exosomes have consequently been evaluated for application in cardiac regeneration and repair. In this review, we summarize the potential mechanisms and therapeutic effects of MSC-derived exosomes in cardiac regeneration and repair and provide evidence to support their clinical application.

Recent advances in the development of nitric oxide-releasing biomaterials and their application potentials in chronic wound healing

Chronic wounds, such as pressure ulcers, vascular ulcers and diabetic foot ulcers (DFUs), often stay in a state of pathological inflammation and suffer from persistent infection, excess inflammation, and hypoxia, thus they are difficult to be healed. Nitric oxide (NO) plays a critical role in the regulation of various wound healing processes, including inflammatory response, cell proliferation, collagen formation, antimicrobial action and angiogenesis. The important role of NO in wound healing attracts intensive research focus on NO-based wound healing therapy. However, the application of NO gas therapy needs to resolve the intrinsic shortcomings of gas therapy, such as short storage and release times as well as temporal and spatial uncontrollability of the release mode. So far, various types of NO donors, including organic nitrates (RONO2), nitrites (RONO), S-nitrosothiols (RSNOs), nitrosamines, N-diazeniumdiolates (NONOates), and metal-NO complexes, have been developed to solidify gaseous NO and they were further encapsulated in or conjugated onto a variety of biomaterial vectors to develop NO delivery systems. NO synthetic enzyme mimics to catalyze the production and release of NO from l-arginine have also been developed. This paper reviews recent advances of NO donors, biomaterial vectors, thus-formed NO delivery systems, as well as recently emerged NO synthetic enzyme mimics. Furthermore, this review also summarizes the functions of NO releasing biomaterials that would benefit chronic wound healing, including antibacterial properties and the promotion of angiogenesis, as well as the convenient combination of light/thermal induced NO release with light/thermal therapies, and the prospects for future developing trends in this area.

Coaxial-printed small-diameter polyelectrolyte-based tubes with an electrostatic self-assembly of heparin and YIGSR peptide for antithrombogenicity and endothelialization

Low patency ratio of small-diameter vascular grafts remains a major challenge due to the occurrence of thrombosis formation and intimal hyperplasia after transplantation. Although developing the functional coating with release of bioactive molecules on the surface of small-diameter vascular grafts are reported as an effective strategy to improve their patency ratios, it is still difficult for current functional coatings cooperating with spatiotemporal control of bioactive molecules release to mimic the sequential requirements for antithrombogenicity and endothelialization. Herein, on basis of 3D-printed polyelectrolyte-based vascular grafts, a biologically inspired release system with sequential release in spatiotemporal coordination of dual molecules through an electrostatic self-assembly was first described. A series of tubes with tunable diameters were initially fabricated by a coaxial extrusion printing method with customized nozzles, in which a polyelectrolyte ink containing of ε-polylysine and sodium alginate was used. Further, dual bioactive molecules, heparin with negative charges and Tyr-Ile-Gly-Ser-Arg (YIGSR) peptide with positive charges were layer-by-layer assembled onto the surface of these 3D-printed tubes. Due to the electrostatic interaction, the sequential release of heparin and YIGSR was demonstrated and could construct a dynamic microenvironment that was thus conducive to the antithrombogenicity and endothelialization. This study opens a new avenue to fabricate a small-diameter vascular graft with a biologically inspired release system based on electrostatic interaction, revealing a huge potential for development of small-diameter artificial vascular grafts with good patency.

New therapeutic approaches of mesenchymal stem cells-derived exosomes

Mesenchymal stem cells (MSCs) have been demonstrated to have a great potential in the treatment of several diseases due to their differentiation and immunomodulatory capabilities and their ability to be easily cultured and manipulated. Recent investigations revealed that their therapeutic effect is largely mediated by the secretion of paracrine factors including exosomes. Exosomes reflect biophysical features of MSCs and are considered more effective than MSCs themselves. Alternative approaches based on MSC-derived exosomes can offer appreciable promise in overcoming the limitations and practical challenges observed in cell-based therapy. Furthermore, MSC-derived exosomes may provide a potent therapeutic strategy for various diseases and are promising candidates for cell-based and cell-free regenerative medicine. This review briefly summarizes the development of MSCs as a treatment for human diseases as well as describes our current knowledge about exosomes: their biogenesis and molecular composition, and how they exert their effects on target cells. Particularly, the therapeutic potential of MSC-derived exosomes in experimental models and recent clinical trials to evaluate their safety and efficacy are summarized in this study. Overall, this paper provides a current overview of exosomes as a new cell-free therapeutic agent.

Application of stem cell-derived exosomes in ischemic diseases: opportunity and limitations

Ischemic diseases characterized by an insufficient blood flow that leads to a decrease in oxygen and nutrient uptake by cells have emerged as an important contributor to both disability and death worldwide. Up-regulation of angiogenesis may be a key factor for the improvement of ischemic diseases. This article searched articles in PubMed with the following keywords: stem cells, exosomes, angiogenesis, ischemic diseases either alone or in grouping form. The most relevant selected items were stem cell-derived exosomes and ischemic diseases. A growing body of evidence indicates that stem cells produce exosomes, which is the novel emerging approach to cell-to-cell communication and offers a new standpoint on known therapeutic strategies of ischemic diseases. Exosomes transport biological molecules such as many types of proteins, RNAs, DNA fragments, signaling molecules, and lipids between cells. Different stem cells release exosomes representing beneficial effects on ischemic diseases as they promote angiogenesis both in vitro and in vivo experiments. Application of exosomes for therapeutic angiogenesis opened new opportunities in the regenerative medicine, however, some limitations regarding exosomes isolation and application remain concerned. In addition, most of the experiments were conducted in preclinical and therefore translation of these results from bench to bed requires more effort in this field. Exosomes from stem cells are a promising tool for the treatment of ischemic diseases. In addition, translation of pre-clinic results into clinic needs further studies in this field.

Extracellular Vesicles from Human Umbilical Cord Mesenchymal Stem Cells Facilitate Diabetic Wound Healing Through MiR-17-5p-mediated Enhancement of Angiogenesis

Endothelial dysfunction caused by persistent hyperglycemia in diabetes is responsible for impaired angiogenesis in diabetic wounds. Extracellular vehicles (EVs) are considered potential therapeutic tools to promote diabetic wound healing. The aim of this study was to investigate the effects of EVs secreted by human umbilical cord mesenchymal stem cells (hucMSC-EVs) on angiogenesis under high glucose (HG) conditions in vivo and in vitro and to explore the underlying mechanisms. In vivo, local application of hucMSC-EVs enhanced wound healing and angiogenesis. In vitro, hucMSC-EVs promoted proliferation, migration, and tube formation by inhibiting phosphatase and tensin homolog (PTEN) expression and activating the AKT/HIF-1α/VEGF pathways. MiR-17-5p was found to be highly enriched in hucMSC-EVs. In vitro, MiR-17-5p agomirs downregulated the expression of PTEN and activated the AKT/HIF-1α/VEGF pathway to promote proliferation, migration, and tube formation in HG-treated HUVECs. In vivo, miR-17-5p agomirs mimicked the effects of hucMSC-EVs on wound healing and angiogenesis, whereas miR-17-5p inhibitors reversed their effects. Our findings suggest that hucMSC-EVs have regenerative and protective effects on HG-induced endothelial cells via transfer of miR-17-5p targeting PTEN/ AKT/HIF-1α/VEGF pathway, thereby accelerating diabetic wound healing. Thus, hucMSC-EVs may be promising therapeutic candidates for improving diabetic wound angiogenesis.

Extracellular Vesicles as Promising Carriers in Drug Delivery: Considerations from a Cell Biologist's Perspective

The use of extracellular vesicles as cell-free therapy is a promising approach currently investigated in several disease models. The intrinsic capacity of extracellular vesicles to encapsulate macromolecules within their lipid bilayer membrane-bound lumen is a characteristic exploited in drug delivery to transport active pharmaceutical ingredients. Besides their role as biological nanocarriers, extracellular vesicles have a specific tropism towards target cells, which is a key aspect in precision medicine. However, the little knowledge of the mechanisms governing the release of a cargo macromolecule in recipient cells and the Good Manufacturing Practice (GMP) grade scale-up manufacturing of extracellular vesicles are currently slowing their application as drug delivery nanocarriers. In this review, we summarize, from a cell biologist's perspective, the main evidence supporting the role of extracellular vesicles as promising carriers in drug delivery, and we report five key considerations that merit further investigation before translating Extracellular Vesicles (EVs) to clinical applications.

3D bioprinting of integral ADSCs-NO hydrogel scaffolds to promote severe burn wound healing

Severe burns are challenging to heal and result in significant death throughout the world. Adipose-derived mesenchymal stem cells (ADSCs) have emerged as a promising treatment for full-thickness burn healing but are impeded by their low viability and efficiency after grafting in vivo. Nitric oxide (NO) is beneficial in promoting stem cell bioactivity, but whether it can function effectively in vivo is still largely unknown. In this study, we bioprinted an efficient biological scaffold loaded with ADSCs and NO (3D-ADSCs/NO) to evaluate its biological efficacy in promoting severe burn wound healing. The integral 3D-ADSCs/NO hydrogel scaffolds were constructed via 3D bioprinting. Our results shown that 3D-ADSCs/NO can enhance the migration and angiogenesis of Human Umbilical Vein Endothelial Cells (HUVECs). Burn wound healing experiments in mice revealed that 3D-ADSCs/NO accelerated the wound healing by promoting faster epithelialization and collagen deposition. Notably, immunohistochemistry of CD31 suggested an increase in neovascularization, supported by the upregulation of vascular endothelial growth factor (VEGF) mRNA in ADSCs in the 3D biosystem. These findings indicated that 3D-ADSC/NO hydrogel scaffold can promote severe burn wound healing through increased neovascularization via the VEGF signalling pathway. This scaffold may be considered a promising strategy for healing severe burns.

Therapeutic Biomaterial Approaches to Alleviate Chronic Limb Threatening Ischemia

Chronic limb threatening ischemia (CLTI) is a severe condition defined by the blockage of arteries in the lower extremities that leads to the degeneration of blood vessels and is characterized by the formation of non-healing ulcers and necrosis. The gold standard therapies such as bypass and endovascular surgery aim at the removal of the blockage. These therapies are not suitable for the so-called "no option patients" which present multiple artery occlusions with a likelihood of significant limb amputation. Therefore, CLTI represents a significant clinical challenge, and the efforts of developing new treatments have been focused on stimulating angiogenesis in the ischemic muscle. The delivery of pro-angiogenic nucleic acid, protein, and stem cell-based interventions have limited efficacy due to their short survival. Engineered biomaterials have emerged as a promising method to improve the effectiveness of these latter strategies. Several synthetic and natural biomaterials are tested in different formulations aiming to incorporate nucleic acid, proteins, stem cells, macrophages, or endothelial cells in supportive matrices. In this review, an overview of the biomaterials used alone and in combination with growth factors, nucleic acid, and cells in preclinical models is provided and their potential to induce revascularization and regeneration for CLTI applications is discussed.

Mesenchymal Stem Cell Derived Extracellular Vesicles for Repairing the Neurovascular Unit after Ischemic Stroke

Ischemic stroke is a debilitating disease and one of the leading causes of long-term disability. During the early phase after ischemic stroke, the blood-brain barrier (BBB) exhibits increased permeability and disruption, leading to an influx of immune cells and inflammatory molecules that exacerbate the damage to the brain tissue. Mesenchymal stem cells have been investigated as a promising therapy to improve the recovery after ischemic stroke. The therapeutic effects imparted by MSCs are mostly paracrine. Recently, the role of extracellular vesicles released by these MSCs have been studied as possible carriers of information to the brain. This review focuses on the potential of MSC derived EVs to repair the components of the neurovascular unit (NVU) controlling the BBB, in order to promote overall recovery from stroke. Here, we review the techniques for increasing the effectiveness of MSC-based therapeutics, such as improved homing capabilities, bioengineering protein expression, modified culture conditions, and customizing the contents of EVs. Combining multiple techniques targeting NVU repair may provide the basis for improved future stroke treatment paradigms.

Extracellular vesicles derived from EphB2-overexpressing bone marrow mesenchymal stem cells ameliorate DSS-induced colitis by modulating immune balance

Background

The bone marrow mesenchymal stem cell (BMSCs)-derived extracellular vesicles (EVs) open up a new avenue for ulcerative colitis (UC) treatment recently, but they are not selectively enriched in targeted tissues. EphB2, a cell-to-cell signaling receptor, is identified as a regulator for inflammatory response, immune homeostasis and cell migration. In this study, we investigated the therapeutic potential and underlying mechanism for EphB2 over-expressing BMSCs derived EVs (EphB2-EVs) in the treatment of UC.

Methods

BMSCs and EVs were obtained and characterized by a series of experiments. Lentivirus vector encoding EphB2 was transfected into BMSCs and verified by qRT-PCR. We analyzed the EphB2-EVs ability of colonic targeting in a DSS-induced colitis model by using confocal microscope and WB. The protective effect of EphB2-EVs in vivo was systematically evaluated by using a series of function experiments.

Results

We successfully constructed EphB2-overexpressing BMSCs derived EVs (EphB2-EVs). Overexpression of EphB2 significantly enhanced the homing of EVs to the damaged colon. In addition, EphB2-EVs were effective to attenuate inflammation in intestinal mucosa and restore the damaged colon tissue by inhibiting the release of proinflammatory cytokines and upregulating the anti-inflammatory mediators. EphB2-EVs effectively reduced the oxidative stress and repaired the intestinal mucosal barrier in the UC rats. Moreover, EphB2-EVs demonstrated a robust immunomodulatory effect to restore immune homeostasis via modulating Th17/Treg balance and restraining STAT3 activation.

Conclusions

Our results suggest that EphB2-EVs have high colonic targeting ability and could mitigate DSS-induced colitis via maintaining colonic immune homeostasis. These findings provide an effective therapeutic strategy for UC treatment in clinic.

Bioengineering strategies for the treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by narrowing and occlusion of arteries supplying the lower extremities. Approximately 200 million people worldwide are affected by PAD. The current standard of operative care is open or endovascular revascularization in which blood flow restoration is the goal. However, many patients are not appropriate candidates for these treatments and are subject to continuous ischemia of their lower limbs. Current research in the therapy of PAD involves developing modalities that induce angiogenesis, but the results of simple cell transplantation or growth factor delivery have been found to be relatively poor mainly due to difficulties in stem cell retention and survival and rapid diffusion and enzymolysis of growth factors following injection of these agents in the affected tissues. Biomaterials, including hydrogels, have the capability to protect stem cells during injection and to support cell survival. Hydrogels can also provide a sustained release of growth factors at the injection site. This review will focus on biomaterial systems currently being investigated as carriers for cell and growth factor delivery, and will also discuss biomaterials as a potential stand-alone method for the treatment of PAD. Finally, the challenges of development and use of biomaterials systems for PAD treatment will be reviewed.

Biogenesis of Extracellular Vesicles Produced from Human-Stem-Cell-Derived Cortical Spheroids Exposed to Iron Oxides

Stem-cell-derived extracellular vesicles (EVs) are promising tools for therapeutic delivery and imaging in the medical research fields. EVs that arise from endosomal compartments or plasma membrane budding consist of exosomes and microvesicles, which range between 30 and 200 nm and 100-1000 nm, respectively. Iron oxide nanoparticles can be used to label stem cells or possibly EVs for magnetic resonance imaging. This could be a novel way to visualize areas in the body that are affected by neurological disorders such as stroke. Human induced pluripotent stem cells (iPSK3 cells) were plated on low-attachment plates and treated with SB431542 and LDN193189 during the first week for the induction of cortical spheroid formation and grown with fibroblast growth factor 2 and cyclopamine during the second week for the neural progenitor cell (iNPC) differentiation. iNPCs were then grown on attachment plates and treated with iron oxide (Fe₃O₄) nanoparticles at different sizes (8, 15, and 30 nm in diameter) and concentrations (0.1, 10, and 100 μM). The spheroids and media collected from these cultures were used for iron oxide detection as well as EV isolation and characterizations, respectively. MTT assay demonstrated that the increased size and concentration of the iron oxide nanoparticles had little effect on the metabolic activity of iNPCs. In addition, the Live/Dead assay showed high viability in all the nanoparticle treated groups and the untreated control. The EVs isolated from these culture groups were analyzed and displayed similar or higher EV counts compared with control. The observed EV size averaged 200-250 nm, and electron microscopy revealed the expected exosome morphology for EVs from all groups. RT-PCR analysis of EV biogenesis markers (CD63, CD81, Alix, TSG101, Syntenin1, ADAM10, RAB27b, and Syndecan) showed differential expression between the iron-oxide-treated cultures and nontreated cultures, as well as between adherent and nonadherent 3D cultures. Iron oxide nanoparticles were detected inside the cortical spheroid cells but not EVs by MRI. The addition of iron oxide nanoparticles does not induce significant cytotoxic effects to cortical spheroids. In addition,, nanoparticles may stimulate the biogenesis of EVs when added to cortical spheroids in vitro.

Polymeric Nitric Oxide Delivery Nanoplatforms for Treating Cancer, Cardiovascular Diseases, and Infection

The shortened Abstract is as follows: Therapeutic gas nitric oxide (NO) has demonstrated the unique advances in biomedical applications due to its prominent role in regulating physiological/pathophysiological activities in terms of vasodilation, angiogenesis, chemosensitizing effect, and bactericidal effect. However, it is challenging to deliver NO, due to its short half-life (<5 s) and short diffusion distances (20-160 µm). To address these, various polymeric NO delivery nanoplatforms (PNODNPs) have been developed for cancer therapy, antimicrobial and cardiovascular therapeutics, because of the important advantages of polymeric delivery nanoplatforms in terms of controlled release of therapeutics and the extremely versatile nature. This reviews highlights the recent significant advances made in PNODNPs for NO storing and targeting delivery. The ideal and unique criteria that are required for PNODNPs for treating cancer, cardiovascular diseases and infection, respectively, are summarized. Hopefully, effective storage and targeted delivery of NO in a controlled manner using PNODNPs could pave the way for NO-sensitized synergistic therapy in clinical practice for treating the leading death-causing diseases.

Mesenchymal stem cell-derived small extracellular vesicles in the treatment of human diseases: Progress and prospect

Mesenchymal stem cells (MSCs) are self-renewing, multipotent cells that could differentiate into multiple tissues. MSC-based therapy has become an attractive and promising strategy for treating human diseases through immune regulation and tissue repair. However, accumulating data have indicated that MSC-based therapeutic effects are mainly attributed to the properties of the MSC-sourced secretome, especially small extracellular vesicles (sEVs). sEVs are signaling vehicles in intercellular communication in normal or pathological conditions. sEVs contain natural contents, such as proteins, mRNA, and microRNAs, and transfer these functional contents to adjacent cells or distant cells through the circulatory system. MSC-sEVs have drawn much attention as attractive agents for treating multiple diseases. The properties of MSC-sEVs include stability in circulation, good biocompatibility, and low toxicity and immunogenicity. Moreover, emerging evidence has shown that MSC-sEVs have equal or even better treatment efficacies than MSCs in many kinds of disease. This review summarizes the current research efforts on the use of MSC-sEVs in the treatment of human diseases and the existing challenges in their application from lab to clinical practice that need to be considered.

The delivery of hsa-miR-11401 by extracellular vesicles can relieve doxorubicin-induced mesenchymal stem cell apoptosis

BACKGROUND

Chemotherapy is an effective anti-tumor treatment. Mesenchymal stem cells (MSCs), exerting therapy effect on injured tissues during chemotherapy, may be damaged in the process. The possibility of self-healing through long-range paracrine and the mechanisms are unclear.

METHODS

Doxorubicin, a commonly used chemotherapy drug, was to treat human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) for 6 h as an in vitro cell model of chemotherapy-induced damage. Then we use extracellular vesicles derived from placental mesenchymal stem cells (hP-MSCs) to investigate the therapeutic potential of MSCs-EVs for chemotherapy injury. The mechanism was explored using microRNA sequencing.

RESULTS

MSC-derived extracellular vesicles significantly alleviated the chemotherapy-induced apoptosis. Using microRNA sequencing, we identified hsa-miR-11401, which was downregulated in the Dox group but upregulated in the EV group. The upregulation of hsa-miR-11401 reduced the expression of SCOTIN, thereby inhibiting p53-dependent cell apoptosis.

CONCLUSIONS

Hsa-miR-11401 expressed by MSCs can be transported to chemotherapy-damaged cells by EVs, reducing the high expression of SCOTIN in damaged cells, thereby inhibiting SCOTIN-mediated apoptosis.

Extracellular Vesicles in Musculoskeletal Pathologies and Regeneration

The incidence of musculoskeletal diseases is steadily increasing with aging of the population. In the past years, extracellular vesicles (EVs) have gained attention in musculoskeletal research. EVs have been associated with various musculoskeletal pathologies as well as suggested as treatment option. EVs play a pivotal role in communication between cells and their environment. Thereby, the EV cargo is highly dependent on their cellular origin. In this review, we summarize putative mechanisms by which EVs can contribute to musculoskeletal tissue homeostasis, regeneration and disease, in particular matrix remodeling and mineralization, pro-angiogenic effects and immunomodulatory activities. Mesenchymal stromal cells (MSCs) present the most frequently used cell source for EV generation for musculoskeletal applications, and herein we discuss how the MSC phenotype can influence the cargo and thus the regenerative potential of EVs. Induced pluripotent stem cell-derived mesenchymal progenitor cells (iMPs) may overcome current limitations of MSCs, and iMP-derived EVs are discussed as an alternative strategy. In the last part of the article, we focus on therapeutic applications of EVs and discuss both practical considerations for EV production and the current state of EV-based therapies.

Extracellular vesicles derived from mesenchymal stem cells: A platform that can be engineered

Mesenchymal stem cells play an important role in tissue damage and repair. This role is mainly due to a paracrine mechanism, and extracellular vesicles (EVs) are an important part of the paracrine function. EVs play a vital role in many aspects of cell homeostasis, physiology, and pathology, and EVs can be used as clinical biomarkers, vaccines, or drug delivery vehicles. A large number of studies have shown that EVs derived from mesenchymal stem cells (MSC-EVs) play an important role in the treatment of various diseases. However, the problems of low production, low retention rate, and poor targeting of MSC-EVs are obstacles to current clinical applications. The engineering transformation of MSC-EVs can make up for those shortcomings, thereby improving treatment efficiency. This review summarizes the latest research progress of MSC-EV direct and indirect engineering transformation from the aspects of improving MSC-EV retention rate, yield, targeting, and MSC-EV visualization research, and proposes some feasible MSC-EV engineering methods of transformation.

Bone marrow stromal cells stimulated by strontium-substituted calcium silicate ceramics: release of exosomal miR-146a regulates osteogenesis and angiogenesis

Dual-functional regulation for angiogenesis and osteogenesis is crucial for desired bone regeneration especially in large-sized bone defects. Exosomes have been demonstrated to facilitate bone regeneration through enhanced osteogenesis and angiogenesis. Moreover, functional stimulation to mesenchymal stromal cells (MSCs) was reported to further boost the pro-angiogenic ability of exosomes secreted. However, whether the stimulation by bioactive trace elements of biomaterials could enhance pro-angiogenic capability of bone marrow stromal cells (BMSCs)-derived exosomes and consequently promote in vivo vascularized bone regeneration has not been investigated. In this study, strontium-substituted calcium silicate (Sr-CS) was chosen and the biological function of BMSCs-derived exosomes after Sr-CS stimulation (Sr-CS-Exo) was systemically investigated. The results showed that Sr-CS-Exo could significantly promote in vitro angiogenesis of human umbilical vein endothelial cells (HUVECs), which might be attributed to elevated pro-angiogenic miR-146a cargos and inhibition of Smad4 and NF2 proteins. Moreover, the in vivo study confirmed that Sr-CS-Exo possessed superior pro-angiogenic ability, which contributed to the accelerated developmental vascularization in zebrafish along with the neovascularization and bone regeneration in rat distal femur defects. Our findings may provide new insights into the mechanisms underlying Sr-containing biomaterials-induced angiogenesis, and for the first time, proposed that Sr-CS-Exo may serve as the candidate engineered-exosomes with dual-functional regulation for angiogenesis and osteogenesis in vascularized bone regeneration.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: A Potential Therapeutic Strategy for Acute Kidney Injury

Acute kidney injury (AKI) is a common and potential life-threatening disease in patients admitted to hospital, affecting 10%-15% of all hospitalizations and around 50% of patients in the intensive care unit. Severe, recurrent, and uncontrolled AKI may progress to chronic kidney disease or end-stage renal disease. AKI thus requires more efficient, specific therapies, rather than just supportive therapy. Mesenchymal stem cells (MSCs) are considered to be promising cells for cellular therapy because of their ease of harvesting, low immunogenicity, and ability to expand in vitro. Recent research indicated that the main therapeutic effects of MSCs were mediated by MSC-derived extracellular vesicles (MSC-EVs). Furthermore, compared with MSCs, MSC-EVs have lower immunogenicity, easier storage, no tumorigenesis, and the potential to be artificially modified. We reviewed the therapeutic mechanism of MSCs and MSC-EVs in AKI, and considered recent research on how to improve the efficacy of MSC-EVs in AKI. We also summarized and analyzed the potential and limitations of EVs for the treatment of AKI to provide ideas for future clinical trials and the clinical application of MSC-EVs in AKI.