Study on the Therapeutic Effects and Mechanisms of Human Mesenchymal Stem Cell-Derived Exosomes Carrying NGF Gene in Treating Ischemic Stroke in Rats

Objective:To investigate the therapeutic effects and mechanisms of human mesenchymal stem cell-derived exosomes(hMSCs-Exo)carrying the NGF gene in treating ischemic stroke in rats,aiming to provide new insights and treatment methods for ischemic stroke therapy.Methods:After successful construction of the cerebral ischemia model in 40 male SPF-grade SD rats aged 6-8 weeks,the model rats were randomly divided into 4 groups:Sham group,PBS group,hMSCs-Exo group,and NGF-hMSCs-Exo group,with 10 rats in each group.The rat MCAO model was prepared using the classic filament method,and NGF-hMSCs-Exo were injected via the tail vein into the MCAO model rats.The expression of the NGF gene in brain ischemic tissues,neuronal regeneration,and rat neurological function recovery were observed using TTC staining,memory function evaluation,Western blot,qRT-PCR,and other methods.Results:Compared with the Sham group,neurological deficits were significant in the PBS group(P<0.01).Compared with the PBS group,neurological scores improved in the hMSCs-Exo group and NGF-hMSCs-Exo group(P<0.05).Compared with the hMSCs-Exo group,the improvement in neurological deficits was more significant in the NGF-hMSCs-Exo group(P<0.05).The infarct area after NGF-hMSCs-Exo intervention was significantly reduced(P<0.05)compared with the Sham group.Compared with the PBS group,relative expression levels of NGF mRNA and protein decreased,while Caspase-3 mRNA and protein expression significantly increased in the PBS group(P<0.01).Compared with the PBS group and hMSCs-Exo group,there were differences in NGF and Caspase-3 mRNA and protein expression in the NGF-hMSCs-Exo group rat brain tissues(P<0.05).Conclusion:Treatment with human mesenchymal stem cell-derived exosomes carrying the NGF gene improves cognitive function and exerts protective effects on SD rats while inhibiting apoptotic levels in cells.

Mesenchymal stem cells’“garbage bags”at work:Treating radial nerve injury with mesenchymal stem cell-derived exosomes

Unlike central nervous system injuries,peripheral nerve injuries(PNIs)are often characterized by more or less successful axonal regeneration.However,structural and functional recovery is a senile process involving multifaceted cellular and molecular processes.The contemporary treatment options are limited,with surgical intervention as the gold-standard method;however,each treatment option has its associated limitations,especially when the injury is severe with a large gap.Recent advancements in cell-based therapy and cell-free therapy approaches using stem cell-derived soluble and insoluble components of the cell secretome are fast-emerging therapeutic approaches to treating acute and chronic PNI.The recent pilot study is a leap forward in the field,which is expected to pave the way for more enormous,systematic,and well-designed clinical trials to assess the therapeutic efficacy of mesenchymal stem cell-derived exosomes as a bio-drug either alone or as part of a combinatorial approach,in an attempt synergize the best of novel treatment approaches to address the complexity of the neural repair and regeneration.

Human umbilical cord mesenchymal stem cell-derived exosomes loaded into a composite conduit promote functional recovery after peripheral nerve injury in rats

Complete transverse injury of peripheral nerves is challenging to treat.Exosomes secreted by human umbilical cord mesenchymal stem cells are considered to play an important role in intercellular communication and regulate tissue regeneration.In previous studies,a collagen/hyaluronic acid sponge was shown to provide a suitable regeneration environment for Schwann cell proliferation and to promote axonal regeneration.This three-dimensional(3D)composite conduit contains a collagen/hyaluronic acid inner sponge enclosed in an electrospun hollow poly(lactic-co-glycolic acid)tube.However,whether there is a synergy between the 3D composite conduit and exosomes in the repair of peripheral nerve injury remains unknown.In this study,we tested a comprehensive strategy for repairing long-gap(10 mm)peripheral nerve injury that combined the 3D composite conduit with human umbilical cord mesenchymal stem cell-derived exosomes.Repair effectiveness was evaluated by sciatic functional index,sciatic nerve compound muscle action potential recording,recovery of muscle mass,measuring the cross-sectional area of the muscle fiber,Masson trichrome staining,and transmission electron microscopy of the regenerated nerve in rats.The results showed that transplantation of the 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes promoted peripheral nerve regeneration and restoration of motor function,similar to autograft transplantation.More CD31-positive endothelial cells were observed in the regenerated nerve after transplantation of the loaded conduit than after transplantation of the conduit without exosomes,which may have contributed to the observed increase in axon regeneration and distal nerve reconnection.Therefore,the use of a 3D composite conduit loaded with human umbilical cord mesenchymal stem cell-derived exosomes represents a promising cell-free therapeutic option for the treatment of peripheral nerve injury.

Human bone marrow mesenchymal stem cell-derived exosomes loaded with gemcitabine inhibit pancreatic cancer cell proliferation by enhancing apoptosis

BACKGROUND Pancreatic cancer remains one of the most lethal malignancies,and has limited effective treatment.Gemcitabine(GEM),a chemotherapeutic agent,is commonly used for clinical treatment of pancreatic cancer,but it has characteristics of low drug delivery efficiency and significant side effects.The study tested the hypothesis that human bone marrow mesenchymal stem cell(MSC)-derived exosomes loaded with GEM(Exo-GEM)would have a higher cytotoxicity against human pancreatic cancer cells by enhancing their apoptosis.AIM To investigate the cytotoxicity of MSC-derived Exo-GEM against pancreatic cancer cells in vitro.METHODS Exosomes were isolated from MSCs and characterized by transmission electron microscopy and nanoparticle tracking analysis.Exo-GEM through electroporation,sonication,or incubation,and the loading efficiency was evaluated.The cytotoxicity of Exo-GEM or GEM alone against human pancreatic cancer Panc-1 and MiaPaca-2 cells was assessed by MTT and flow cytometry assays.RESULTS The isolated exosomes had an average size of 76.7 nm.The encapsulation efficacy and loading efficiency of GEM by electroporation and sonication were similar and significantly better than incubation.The cytotoxicity of Exo-GEM against pancreatic cancer cells was stronger than free GEM and treatment with 0.02μM Exo-GEM significantly reduced the viability of both Panc-1 and MiaPaca-2 cells.Moreover,Exo-GEM enhanced the frequency of GEMinduced apoptosis in both cell lines.CONCLUSION Human bone marrow MSC-derived Exo-GEM have a potent cytotoxicity against human pancreatic cancer cells by enhancing their apoptosis,offering a promising drug delivery system for improving therapeutic outcomes.

Mesenchymal stem cell-derived exosomes regulate microglia phenotypes:a promising treatment for acute central nervous system injury

There is growing evidence that long-term central nervous system(CNS)inflammation exacerbates secondary deterioration of brain structures and functions and is one of the major determinants of disease outcome and progression.In acute CNS injury,brain microglia are among the first cells to respond and play a critical role in neural repair and regeneration.However,microglial activation can also impede CNS repair and amplify tissue damage,and phenotypic transformation may be responsible for this dual role.Mesenchymal stem cell(MSC)-derived exosomes(Exos)are promising therapeutic agents for the treatment of acute CNS injuries due to their immunomodulatory and regenerative properties.MSC-Exos are nanoscale membrane vesicles that are actively released by cells and are used clinically as circulating biomarkers for disease diagnosis and prognosis.MSC-Exos can be neuroprotective in several acute CNS models,including for stroke and traumatic brain injury,showing great clinical potential.This review summarized the classification of acute CNS injury disorders and discussed the prominent role of microglial activation in acute CNS inflammation and the specific role of MSC-Exos in regulating pro-inflammatory microglia in neuroinflammatory repair following acute CNS injury.Finally,this review explored the potential mechanisms and factors associated with MSCExos in modulating the phenotypic balance of microglia,focusing on the interplay between CNS inflammation,the brain,and injury aspects,with an emphasis on potential strategies and therapeutic interventions for improving functional recovery from early CNS inflammation caused by acute CNS injury.

Treadmill exercise exerts a synergistic effect with bone marrow mesenchymal stem cell-derived exosomes on neuronal apoptosis and synaptic-axonal remodeling

Treadmill exercise and mesenchymal stem cell transplantation are both practical and effective methods for the treatment of cerebral ischemia.However,whether there is a synergistic effect between the two remains unclear.In this study,we established rat models of ischemia/reperfusion injury by occlusion of the middle cerebral artery for 2 hours and reperfusion for 24 hours.Rat models were perfused with bone marrow mesenchymal stem cell-derived exosomes(MSC-exos)via the tail vein and underwent 14 successive days of treadmill exercise.Neurological assessment,histopathology,and immunohistochemistry results revealed decreased neuronal apoptosis and cerebral infarct volume,evident synaptic formation and axonal regeneration,and remarkably recovered neurological function in rats subjected to treadmill exercise and MSC-exos treatment.These effects were superior to those in rats subjected to treadmill exercise or MSC-exos treatment alone.Mechanistically,further investigation revealed that the activation of JNK1/c-Jun signaling pathways regulated neuronal apoptosis and synaptic-axonal remodeling.These findings suggest that treadmill exercise may exhibit a synergistic effect with MSC-exos treatment,which may be related to activation of the JNK1/c-Jun signaling pathway.This study provides novel theoretical evidence for the clinical application of treadmill exercise combined with MSC-exos treatment for ischemic cerebrovascular disease.

Immunomodulation:The next target of mesenchymal stem cell-derived exosomes in the context of ischemic stroke

Ischemic stroke(IS)is the most prevalent form of brain disease,characterized by high morbidity,disability,and mortality.However,there is still a lack of ideal prevention and treatment measures in clinical practice.Notably,the trans-plantation therapy of mesenchymal stem cells(MSCs)has been a hot research topic in stroke.Nevertheless,there are risks associated with this cell therapy,including tumor formation,coagulation dysfunction,and vascular occlusion.Also,a growing number of studies suggest that the therapeutic effect after transplantation of MSCs is mainly attributed to MSC-derived exosomes(MSC-Exos).And this cell-free mediated therapy appears to circumvent many risks and difficulties when compared to cell therapy,and it may be the most promising new strategy for treating stroke as stem cell replacement therapy.Studies suggest that suppressing inflammation via modulation of the immune response is an additional treatment option for IS.Intriguingly,MSC-Exos mediates the inflam-matory immune response following IS by modulating the central nervous system,the peripheral immune system,and immunomodulatory molecules,thereby promoting neurofunctional recovery after stroke.Thus,this paper reviews the role,potential mechanisms,and therapeutic potential of MSC-Exos in post-IS inflammation in order to identify new research targets.

The role of mesenchymal stem cell-derived exosomes in tumor progression

Exosomes derived from mesenchymal stem cells(MSC-Exos)are nano-sized extracellular vesicles enriched with bioactive molecules,such as microRNAs,enzymes,cytokines,chemokines,immunomodulatory,trophic,and growth factors.These molecules regulate the survival,phenotype,and function of malignant and tumor-infiltrated immune cells.Due to their nano-size and bilayer lipid envelope,MSC-Exos can easily bypass biological barriers and may serve as drug carriers to deliver chemotherapeutics directly into the tumor cells.Here,we summarize current knowledge regarding molecular mechanisms responsible for MSC-Exos-dependent modulation of tumor progression and discuss insights regarding the therapeutic potential of MSC-Exos in the treatment of malignant diseases.

Novel frontiers for bone regeneration:application progress of mesenchymal stem cell-derived exosomes in bone tissue engineering

Identifying an effective way to promote bone regeneration for patients who suffer from bone defects is urgently demanded.In recent years,mesenchymal stem cells(MSCs)have drawed wide attention in bone regeneration.Besides,several studies have indicated the secretions of MSCs,especially exosomes,play a vital role in bone regeneration process.Exosomes can transfer“cargos”of proteins,RNA,DNA,lipids,to regulate fate of recipient cells by affecting their proliferation,differentiation,migration and gene expression.In this paper,the application of MSCs-derived exosomes in bone tissue engineering is reviewed,and the potential therapeutic role of exosome microRNA in bone regeneration is emphasized.

Mesenchymal stem cell-derived exosomes: Toward cell-free therapeutic strategies in regenerative medicine

Mesenchymal stem cells(MSCs)are multipotent stem cells with marked potential for regenerative medicine because of their strong immunosuppressive and regenerative abilities.The therapeutic effects of MSCs are based in part on their secretion of biologically active factors in extracellular vesicles known as exosomes.Exosomes have a diameter of 30-100 nm and mediate intercellular communication and material exchange.MSC-derived exosomes(MSC-Exos)have potential for cell-free therapy for diseases of,for instance,the kidney,liver,heart,nervous system,and musculoskeletal system.Hence,MSC-Exos are an alternative to MSCbased therapy for regenerative medicine.We review MSC-Exos and their therapeutic potential for a variety of diseases and injuries.

Mesenchymal stem cell-derived exosomes promote neurogenesis and cognitive function recovery in a mouse model of Alzheimer’s disease

Studies have shown that mesenchymal stem cell-derived exosomes can enhance neural plasticity and improve cognitive impairment.The purpose of this study was to investigate the effects of mesenchymal stem cell-derived exosomes on neurogenesis and cognitive capacity in a mouse model of Alzheimer’s disease.Alzheimer’s disease mouse models were established by injection of beta amyloid 1?42 aggregates into dentate gyrus bilaterally.Morris water maze and novel object recognition tests were performed to evaluate mouse cognitive deficits at 14 and 28 days after administration.Afterwards,neurogenesis in the subventricular zone was determined by immunofluorescence using doublecortin and PSA-NCAM antibodies.Results showed that mesenchymal stem cells-derived exosomes stimulated neurogenesis in the subventricular zone and alleviated beta amyloid 1?42-induced cognitive impairment,and these effects are similar to those shown in the mesenchymal stem cells.These findings provide evidence to validate the possibility of developing cell-free therapeutic strategies for Alzheimer’s disease.All procedures and experiments were approved by Institutional Animal Care and Use Committee(CICUAL)(approval No.CICUAL 2016-011)on April 25,2016.

Multifunctional role of microRNAs in mesenchymal stem cell-derived exosomes in treatment of diseases

Mesenchymal stem cells can be replaced by exosomes for the treatment of inflammatory diseases,injury repair,degenerative diseases,and tumors.Exosomes are small vesicles rich in a variety of nucleic acids[including messenger RNA,Long non-coding RNA,microRNA(miRNA),and circular RNA],proteins,and lipids.Exosomes can be secreted by most cells in the human body and are known to play a key role in the communication of information and material transport between cells.Like exosomes,miRNAs were neglected before their role in various activities of organisms was discovered.Several studies have confirmed that miRNAs play a vital role within exosomes.This review focuses on the specific role of miRNAs in MSC-derived exosomes(MSC-exosomes)and the methods commonly used by researchers to study miRNAs in exosomes.Taken together,miRNAs from MSC-exosomes display immense potential and practical value,both in basic medicine and future clinical applications,in treating several diseases.

Mesenchymal stem cell-derived exosomes:An emerging therapeutic strategy for normal and chronic wound healing

Skin wound healing is a complex biological process.Mesenchymal stem cells(MSCs)play an important role in skin wound repair due to their multidirectional differentiation potential,hematopoietic support,promotion of stem cell implantation,self-replication,and immune regulation.Exosomes are vesicles with diameters of 40-100 nm that contain nucleic acids,proteins,and lipids and often act as mediators of cell-to-cell communication.Currently,many clinical scientists have carried out cell-free therapy for skin wounds,especially chronic wounds,using exosomes derived from MSCs.This review focuses on the latest research progress on the mechanisms of action associated with the treatment of wound healing with exosomes derived from different MSCs,the latest research progress on the combination of exosomes and other biological or nonbiological factors for the treatment of chronic skin wounds,and the new prospects and development goals of cell-free therapy.

Mesenchymal stem cell-derived exosomes: A novel and potential remedy for cutaneous wound healing and regeneration

Poor healing of cutaneous wounds is a common medical problem in the field of traumatology.Due to the intricate pathophysiological processes of wound healing,the use of conventional treatment methods,such as chemical molecule drugs and traditional dressings,have been unable to achieve satisfactory outcomes.Within recent years,explicit evidence suggests that mesenchymal stem cells(MSCs)have great therapeutic potentials on skin wound healing and regeneration.However,the direct application of MSCs still faces many challenges and difficulties.Intriguingly,exosomes as cell-secreted granular vesicles with a lipid bilayer membrane structure and containing specific components from the source cells may emerge to be excellent substitutes for MSCs.Exosomes derived from MSCs(MSC-exosomes)have been demonstrated to be beneficial for cutaneous wound healing and accelerate the process through a variety of mechanisms.These mechanisms include alleviating inflammation,promoting vascularization,and promoting proliferation and migration of epithelial cells and fibroblasts.Therefore,the application of MSC-exosomes may be a promising alternative to cell therapy in the treatment of cutaneous wounds and could promote wound healing through multiple mechanisms simultaneously.This review will provide an overview of the role and the mechanisms of MSC-derived exosomes in cutaneous wound healing,and elaborate the potentials and future perspectives of MSC-exosomes application in clinical practice.

Mesenchymal stem cell-derived exosomes inhibit the VEGF-A expression in human retinal vascular endothelial cells induced by high glucose

AIM:To determine the effect of exosomes derived from human umbilical cord blood mesenchymal stem cells(hUCMSCs)on the expression of vascular endothelial growth factor A(VEGF-A)in human retinal vascular endothelial cells(HRECs).METHODS:Exosomes were isolated from hUCMSCs using cryogenic ultracentrifugation and characterized by transmission electron microscopy,Western blotting and nanoparticle tracking analysis.HRECs were randomly divided into a normal control group(group A),a high glucose model group(group B),a high glucose group with 25μg/mL(group C),50μg/mL(group D),and 100μg/mL exosomes(group E).Twenty-four hours after coculture,the cell proliferation rate was detected using flow cytometry,and the VEGF-A level was detected using immunofluorescence.After coculture 8,16,and 24h,the expression levels of VEGF-A in each group were detected using PCR and Western blots.RESULTS:The characteristic morphology(membrane structured vesicles)and size(diameter between 50 and 200 nm)were observed under transmission electron microscopy.The average diameter of 122.7 nm was discovered by nanoparticle tracking analysis(NTA).The exosomal markers CD9,CD63,and HSP70 were strongly detected.The proliferation rate of the cells in group B increased after 24h of coculture.Immunofluorescence analyses revealed that the upregulation of VEGF-A expression in HRECs stimulated by high glucose could be downregulated by cocultured hUCMSC-derived exosomes(F=39.03,P<0.01).The upregulation of VEGF-A protein(group C:F=7.96;group D:F=17.29;group E:F=11.89;8h:F=9.45;16h:F=12.86;24h:F=42.28,P<0.05)and mRNA(group C:F=4.137;group D:F=13.64;group E:F=22.19;8h:F=7.253;16h:F=16.98;24h:F=22.62,P<0.05)in HRECs stimulated by high glucose was downregulated by cocultured hUCMSC-derived exosomes(P<0.05).CONCLUSION:hUCMSC-derived exosomes downregulate VEGF-A expression in HRECs stimulated by high glucose in time and concentration dependent manner.

Mesenchymal stem cell-derived exosomes: The dawn of diabetic wound healing

Chronic wound healing has long been an unmet medical need in the field of wound repair,with diabetes being one of the major etiologies.Diabetic chronic wounds(DCWs),especially diabetic foot ulcers,are one of the most threatening chronic complications of diabetes.Although the treatment strategies,drugs,and dressings for DCWs have made great progress,they remain ineffective in some patients with refractory wounds.Stem cell-based therapies have achieved specific efficacy in various fields,with mesenchymal stem cells(MSCs)being the most widely used.Although MSCs have achieved good feedback in preclinical studies and clinical trials in the treatment of cutaneous wounds or other situations,the potential safety concerns associated with allogeneic/autologous stem cells and unknown long-term health effects need further attention and supervision.Recent studies have reported that stem cells mainly exert their trauma repair effects through paracrine secretion,and exosomes play an important role in intercellular communication as their main bioactive component.MSC-derived exosomes(MSC-Exos)inherit the powerful inflammation and immune modulation,angiogenesis,cell proliferation and migration promotion,oxidative stress alleviation,collagen remodeling imbalances regulation of their parental cells,and can avoid the potential risks of direct stem cell transplantation to a large extent,thus demonstrating promising performance as novel"cell-free"therapies in chronic wounds.This review aimed to elucidate the potential mechanism and update the progress of MSC-Exos in DCW healing,thereby providing new therapeutic directions for DCWs that are difficult to be cured using conventional therapy.

Protective effect of human umbilical cord mesenchymal stem cell-derived exosomes on rat retinal neurons in hyperglycemia through the brain-derived neurotrophic factor/TrkB pathway

AIM:To explore whether human umbilical cord mesenchymal stem cell(hUCMSC)-derived exosomes(hUCMSC-Exos)protect rat retinal neurons in high-glucose(HG)conditions by activating the brain-derived neurotrophic factor(BDNF)-Trk B pathway.METHODS:h UCMSC-Exos were collected with differential ultracentrifugation methods and observed by transmission electron microscopy.Enzyme-linked immunosorbent assays(ELISAs)was used to quantify BDNF in hUCMSC-Exos,and Western blot was used to identify surface markers of hUCMSC-Exos.Rat retinal neurons were divided into 4 groups.Furthermore,cell viability,cell apoptosis,and TrkB protein expression were measured in retinal neurons.RESULTS:hUCMSCs and isolated hUCMSC-Exos were successfully cultured.All hUCMSC-Exos showed a diameter of 30 to 150 nm and had a phospholipid bimolecular membrane structure,as observed by transmission electron microscopy.ELISA showed the BDNF concentration of hUCMSCs-Exos was 2483.16±281.75.hUCMSCs-Exos effectively reduced the apoptosis of retinal neuron rate and improved neuron survival rate,meanwhile,the results of immunofluorescence verified the fluorescence intensity of TrKB in neurons increased.And all above effects were reduced by treated hUCMSCs-Exos with BDNF inhibitors.hUCMSC-Exos effectively reduced the apoptosis rate of retinal neurons by activating the BDNF-TrkB pathway in a HG environment.CONCLUSION:In the HG environment,hUCMSC-Exos could carry BDNF into rat retinal neurons,inhibiting neuronal apoptosis by activating the BDNF-TrkB pathway.

Mesenchymal stem cell-derived exosomes for gastrointestinal cancer

Gastrointestinal(GI)malignancies,a series of malignant conditions originating from the digestive system,include gastric cancer,hepatocellular carcinoma,pancreatic cancer,and colorectal cancer.GI cancers have been regarded as the leading cancer-related cause of death in recent years.Therefore,it is essential to develop effective treatment strategies for GI malignancies.Mesenchymal stem cells(MSCs),a type of distinct non-hematopoietic stem cells and an important component of the tumor microenvironment,play important roles in regulating GI cancer development and progression through multiple mechanisms,such as secreting cytokines and direct interactions.Currently,studies are focusing on the anti-cancer effect of MSCs on GI malignancies.However,the effects and functional mechanisms of MSC-derived exosomes on GI cancer are less studied.MSC-derived exosomes can regulate GI tumor growth,drug response,metastasis,and invasion through transplanting proteins and miRNA to tumor cells to activate the specific signal pathway.Besides,the MSC-derived exosomes are also seen as an important drug delivery system and have shown potential in anti-cancer treatment.This study aims to summarize the effect and biological functions of MSC-derived exosomes on the development of GI cancers and discuss their possible clinical applications for the treatment of GI malignancies.

Modulation Effects of the 3D Strain Microenvironment on Characteristics of Mesenchymal Stem Cell-Derived Exosomes

It is necessary to investigate the characteristics of Mesenchymal stem cells(MSCs)derived exosomes,and especially their application in tissue regeneration.Previous studies have shown that inflammatory stimulation enhanced the secretion of MSC-derived exosomes with stronger anti-inflammatory protein,cytokine profiles,and functional RNA via altering COX2/PGE2 pathway.Recently,accumulating evidence has also revealed that biophysical cues(especially biomechanical cues)in cell microenvironment have significant effects not only on cells but also on their exosomes.It has been reported that applying bi-axial strain to MSCs induces formation of a stiffer cytoskeleton through mTORC2 signaling,which biases against adipogenic differentiation and toward osteoblastogenesis.At the same time,For example,dimensionality,composition and stiffness of the extracellular matrix(ECM)has been proved to affect the size and composition of exosomes secreted by cancer cells.However,the effects of biomechanical cues in the three-dimensional(3D)microenvironment on stem cell-derived exosomes remains to be unveiled.Therefore,it is important to understand the roles of 3D cell mechanical microenvironment in regulating the characteristics of stem cell-derived exosomes and develop more efficient approaches to enhance their functions.This study aimed to explore the changes in characteristics of exosomes secreted by MSCs in periodontium in response to the matrix strain in 3D.Periodontal ligament stem cells(PDLSCs)were cultured in a 3D strain microenvironment engineered with microscale magnetically stretched collagen hydrogels.The morphology,particle distribution,marker protein expression of PDLSC-derived exosomes were analyzed.Then the pro-osteogenic property of exosomes was evaluated by assessing cell viability,proliferation,migration and osteogenic differentiation of target cells,for instance human bone marrow mesenchymal stem cells(hBMSCs).Detailed characterizations revealed that PDLSC-derived exosomes in the 3D strain mi-croenvironment were with similar morphology,particle distribution and surface markers.Notably,Exosomes secreted by PDLSCs in strain microenvironment were more endocytosed by hBMSCs and were more potent in improving proliferation and migration of hBMSCs,comparing with PDLSCs in non-strain environment.Alizarin red staining and molecular biology experiments confirmed that treatment of exosomes secreted by PDLSCs under mechanical stimulation led to a significant increase in osteogenic differentiation of hBMSCs in vitro.Meanwhile,in vivo study also indicated that PDLSC-derived exosomes obtained from the 3D strain microenvironment could obviously promote new bone formation.Our findings revealed that mechanical cues profoundly affected the characteristics of PDLSC-derived exosomes,especially for their bio-activity,providing a foundation for using the 3D mechanical microenvironment to enhance the osteo-inductive functions of stem cell-derived exosomes in cell-free therapy for bone regeneration.

Mesenchymal stem cell-derived exosomes as new remedy for the treatment of inflammatory eye diseases

Detrimental immune response has a crucially important role in the development and progression of inflammatory eye diseases.Inflammatory mediators and proteolytic enzymes released by activated immune cells induce serious injury of corneal epithelial cells and retinal ganglion cell which may result in the vision loss.Mesenchymal stem cells(MSCs)are regulatory cells which produce various immunosuppressive factors that modulate phenotype and function of inflammatory immune cells.However,several safety issues,including undesired differentiation and emboli formation,limit clinical use of MSCs.MSC-derived exosomes(MSC-Exos)are nano-sized extracellular vesicles which contain all MSC-derived immunoregulatory factors.Intraocular administration of MSCExos efficiently attenuated eye inflammation and significantly improved visual acuity in experimental animals without causing any severe side effects.As cell-free product,MSC-Exos addressed all safety issues related to the transplantation of MSCs.Therefore,MSC-Exos could be considered as potentially new remedy for the treatment of inflammatory eye diseases which efficacy should be explored in up-coming clinical trials.