Lineage-specific exosomes could override extracellular matrix mediated human mesenchymal stem cell differentiation

Exosomes derived from bone marrow mesenchymal stem cell preconditioned by low-intensity pulsed ultrasound stimulation promote bone-tendon interface fibrocartilage regeneration and ameliorate rotator cuff fatty infiltration

Background

Fibrovascular scar healing of bone-tendon interface (BTI) instead of functional fibrocartilage regeneration is the main concern associated with unsatisfactory prognosis in rotator cuff repair. Mesenchymal stem cells (MSCs) exosomes have been reported to be a new promising cell-free approach for rotator cuff healing. Whereas, controversies abound in whether exosomes of native MSCs alone can effectively induce chondrogenesis.

Purpose

To explore the effect of exosomes derived from low-intensity pulsed ultrasound stimulation (LIPUS)-preconditioned bone marrow mesenchymal stem cells (LIPUS-BMSC-Exos) or un-preconditioned BMSCs (BMSC-Exos) on rotator cuff healing and the underlying mechanism.

Methods

C57BL/6 mice underwent unilateral supraspinatus tendon detachment and repair were randomly assigned to saline, BMSCs-Exos or LIPUS-BMSC-Exos injection therapy. Histological, immunofluorescent and biomechanical tests were detected to investigate the effect of exosomes injection on BTI healing and muscle fatty infiltration of the repaired rotator cuff. In vitro, native BMSCs were incubated with BMSC-Exos or LIPUS-BMSC-Exos and then chondrogenic/adipogenic differentiation were observed. Further, quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the chondrogenesis/adipogenesis-related miRNA profiles of LIPUS-BMSC-Exos and BMSC-Exos. The chondrogenic/adipogenic potential of the key miRNA was verified through function recover test with its mimic and inhibitor.

Results

The results indicated that the biomechanical properties of the supraspinatus tendon-humeral junction were significantly improved in the LIPUS-BMSC-Exos group than that of the BMSCs-Exos group. The LIPUS-BMSC-Exos group also exhibited a higher histological score and more newly regenerated fibrocartilage at the repair site at postoperative 2 and 4 weeks and less fatty infiltration at 4 weeks than the BMSCs-Exos group. In vitro, co-culture of BMSCs with LIPUS-BMSC-Exos could significantly promote BMSCs chondrogenic differentiation and inhibit adipogenic differentiation. Subsequently, qRT-PCR revealed significantly higher enrichment of chondrogenic miRNAs and less enrichment of adipogenic miRNAs in LIPUS-BMSC-Exos compared with BMSC-Exos. Moreover, we demonstrated that this chondrogenesis-inducing potential was primarily attributed to miR-140, one of the most abundant miRNAs in LIPUS-BMSC-Exos.

Conclusion

LIPUS-preconditioned BMSC-Exos can effectively promote BTI fibrocartilage regeneration and ameliorate supraspinatus fatty infiltration by positive regulation of pro-chondrogenesis and anti-adipogenesis, which was primarily through delivering miR-140.

The translational potential of this article

These findings propose an innovative "LIPUS combined Exosomes strategy" for rotator cuff healing which combines both physiotherapeutic and biotherapeutic advantages. This strategy possesses a good translational potential as a local injection of LIPUS preconditioned BMSC-derived Exos during operation can be not only efficient for promoting fibrocartilage regeneration and ameliorating rotator cuff fatty infiltration, but also time-saving, simple and convenient for patients.

High-precision bioactive scaffold with dECM and extracellular vesicles targeting 4E-BP inhibition for cartilage injury repair

The restoration of cartilage injuries remains a formidable challenge in orthopedics, chiefly attributed to the absence of vascularization and innervation in cartilage. Decellularized extracellular matrix (dECM) derived from cartilage, following antigenic removal through decellularization processes, has exhibited remarkable biocompatibility and bioactivity, rendering it a viable candidate for cartilage repair. Additionally, extracellular vesicles (EVs) generated from cartilage have demonstrated a synergistic effect when combined with dECM, potentially mitigating the inhibitory impact on protein synthesis by phosphorylating 4ebp, thereby promoting the synthesis of cartilage-related proteins such as collagen. In pursuit of this objective, we have innovated a novel bioink and repair scaffold characterized by exceptional biocompatibility, bioactivity, and biodegradability, establishing a tissue-specific microenvironment conducive to chondrogenesis. Within rat osteochondral defects, the biologically active scaffold successfully prompted the formation of transparent cartilage, featuring adequate mechanical strength, favorable elasticity, and dECM deposition indicative of cartilage. In summary, this study has effectively engineered a hydrogel bioink tailored for cartilage repair and devised a bioactive cartilage repair scaffold proficient in instigating cell differentiation and fostering cartilage repair.

Global scientific trends on exosomes therapy for osteoporosis from 2004 to 2023: A bibliometric and visualized analysis

BACKGROUND

Exosomes have emerged as pivotal mediators in modulating physiological and pathological processes implicated in osteoporosis (OP) through their distinctive mode of intracellular communication. The use of exosomes has evoked considerable interest, catalyzing a surge in research endeavors on a global scale. This study endeavors to scrutinize contemporary landscapes and burgeoning trends in this realm.

METHODS

The Web of Science Core Collection was used to retrieve publications on exosomes therapy for OP within the time frame of January 1, 2004 to December 31, 2023. The bibliometric methodology was applied to study and index the collected data. VOSviewer and citespace software were used to conduct visualization, co-authorship, co-occurrence, and publication trend analyses of exosome therapy in OP.

RESULTS

A total of 610 publications (443 articles and 167 reviews) from 51 countries and 911 institutions were included in this study. Shanghai Jiao Tong University, Central South University, Sichuan University, and Zhejiang University are leading research institutions in this field. Stem Cell Research Therapy published the highest number of articles and has emerged as the most cited journal. Of the 4077 scholars who participated in the study, Xie, Hui, Zhang, Yan, Tan, and Yi-Juan had the largest number of articles. Furthermore, according to the cluster analysis of external keywords, future research hotspots can be categorized into 3 directions: research status of exosomes for the treatment of OP, treatment of OP through exosome-regulated signaling pathways, and exosomes as targeted drug delivery systems.

CONCLUSION

This study suggests that the number of future publications on exosome therapy for OP will increase, with a focus on fundamental investigations into drug-loading capacities and molecular mechanisms. In summary, this study presents the first systematic bibliometric analysis of exosome therapy publications in OP, providing an objective and comprehensive overview of the field and a valuable reference for researchers in this domain.

New-QiangGuYin-Containing Serum Inhibits Osteoclast-Derived Exosome Secretion and Down-Regulates Notum to Promote Osteoblast Differentiation

New-QiangGuYin (N-QGY), the addition of sea buckthorn on the basis of QGY formula, is herbal formula widely used clinically in China for the treatment of osteoporosis (OP), but its mechanism warrants further exploration. The mechanisms of QGY and N-QGY in the treatment of OP are probed from the perspective of osteoclast-osteoblast balance. Thirty Sprague-Dawley rats are randomly divided into N-QGY group, QGY group, and Control group. Beyond control rats that orally took normal saline, other rats are orally administered with isometric N-QGY or QGY twice every day for 3 days. The drug-containing serum and control serum are prepared and their effects on osteoclast-derived exosome secretion are determined by bicinchoninic acid assay (BCA), nanoparticle tracking analysis, and Western blot. GW4869 and Interleukin-1β (IL-1β) are adopted as the exosome inhibitor and inducer, respectively. Exosome uptake, cell counting kit-8, alkaline phosphatase (ALP) staining, alizarin red staining, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and Western blot are performed to examine the effects of altered osteoclast exosome content on osteogenic differentiation of mesenchymal stem cells (MSCs). N-QGY, QGY, and GW4869 inhibit osteoclast-derived exosome secretion and exosome uptake by MSCs, whereas IL-1β exerted the opposite effects (p < 0.05). Different from IL-1β, N-QGY, QGY, and GW4869 partially elevated MSC viability, osteocalcin secretion, ALP, RUNX Family Transcription Factor 2 (RUNX2) and Osteopontin (OPN) expressions, and calcium deposition in the osteoclast-MSCs coculture system (p < 0.05). Mechanically, osteoclasts increased Notum protein level but decreased β-catenin level, which is enhanced by IL-1β but is reversed by GW4869, QGY, and N-QGY (p < 0.05). And the effect of N-QGY is more conspicuous than that of QGY (P<0.05). N-QGY-containing serum inhibits exosome levels in osteoclasts, thereby enhancing osteogenic differentiation of MSCs via inhibition of Notum protein and promotion of β-catenin protein.

Transfer of cardiomyocyte-derived extracellular vesicles to neighboring cardiac cells requires tunneling nanotubes during heart development

Rationale: Extracellular vesicles (EVs) are thought to mediate intercellular communication during development and disease. Yet, biological insight to intercellular EV transfer remains elusive, also in the heart, and is technically challenging to demonstrate. Here, we aimed to investigate biological transfer of cardiomyocyte-derived EVs in the neonatal heart. Methods: We exploited CD9 as a marker of EVs, and generated two lines of cardiomyocyte specific EV reporter mice: Tnnt2-Cre; double-floxed inverted CD9/EGFP and αMHC-MerCreMer; double-floxed inverted CD9/EGFP. The two mouse lines were utilized to determine whether developing cardiomyocytes transfer EVs to other cardiac cells (non-myocytes and cardiomyocytes) in vitro and in vivo and investigate the intercellular transport pathway of cardiomyocyte-derived EVs. Results: Genetic tagging of cardiomyocytes was confirmed in both reporter mouse lines and proof of concept in the postnatal heart showed that, a fraction of EGFP+/MYH1- non-myocytes exist firmly demonstrating in vivo cardiomyocyte-derived EV transfer. However, two sets of direct and indirect EGFP +/- cardiac cell co-cultures showed that cardiomyocyte-derived EGFP+ EV transfer requires cell-cell contact and that uptake of EGFP+ EVs from the medium is limited. The same was observed when co-cultiring with mouse macrophages. Further mechanistic insight showed that cardiomyocyte EV transfer occurs through type I tunneling nanotubes. Conclusion: While the current notion assumes that EVs are transferred through secretion to the surroundings, our data show that cardiomyocyte-derived EV transfer in the developing heart occurs through nanotubes between neighboring cells. Whether these data are fundamental and relate to adult hearts and other organs remains to be determined, but they imply that the normal developmental process of EV transfer goes through cell-cell contact rather than through the extracellular compartment.

Non-bone-derived exosomes: a new perspective on regulators of bone homeostasis

Accumulating evidence indicates that exosomes help to regulate bone homeostasis. The roles of bone-derived exosomes have been well-described; however, recent studies have shown that some non-bone-derived exosomes have better bone targeting ability than bone-derived exosomes and that their performance as a drug delivery vehicle for regulating bone homeostasis may be better than that of bone-derived exosomes, and the sources of non-bone-derived exosomes are more extensive and can thus be better for clinical needs. Here, we sort non-bone-derived exosomes and describe their composition and biogenesis. Their roles and specific mechanisms in bone homeostasis and bone-related diseases are also discussed. Furthermore, we reveal obstacles to current research and future challenges in the practical application of exosomes, and we provide potential strategies for more effective application of exosomes for the regulation of bone homeostasis and the treatment of bone-related diseases. Video Abstract.

EVs from cells at the early stages of chondrogenesis delivered by injectable SIS dECM promote cartilage regeneration

Articular cartilage defect therapy is still dissatisfactory in clinic. Direct cell implantation faces challenges, such as tumorigenicity, immunogenicity, and uncontrollability. Extracellular vesicles (EVs) based cell-free therapy becomes a promising alternative approach for cartilage regeneration. Even though, EVs from different cells exhibit heterogeneous characteristics and effects. The aim of the study was to discover the functions of EVs from the cells during chondrogenesis timeline on cartilage regeneration. Here, bone marrow mesenchymal stem cells (BMSCs)-EVs, juvenile chondrocytes-EVs, and adult chondrocytes-EVs were used to represent the EVs at different differentiation stages, and fibroblast-EVs as surrounding signals were also joined to compare. Fibroblasts-EVs showed the worst effect on chondrogenesis. While juvenile chondrocyte-EVs and adult chondrocyte-EVs showed comparable effect on chondrogenic differentiation as BMSCs-EVs, BMSCs-EVs showed the best effect on cell proliferation and migration. Moreover, the amount of EVs secreted from BMSCs were much more than that from chondrocytes. An injectable decellularized extracellular matrix (dECM) hydrogel from small intestinal submucosa (SIS) was fabricated as the EVs delivery platform with natural matrix microenvironment. In a rat model, BMSCs-EVs loaded SIS hydrogel was injected into the articular cartilage defects and significantly enhanced cartilage regeneration in vivo. Furthermore, protein proteomics revealed BMSCs-EVs specifically upregulated multiple metabolic and biosynthetic processes, which might be the potential mechanism. Thus, injectable SIS hydrogel loaded with BMSCs-EVs might be a promising therapeutic way for articular cartilage defect.

Microvesicles facilitate the differentiation of mesenchymal stem cells into pancreatic beta-like cells via miR-181a-5p/150-5p

Transplantation of pancreatic islet cells is a promising strategy for the long-term treatment of type 1 diabetes (T1D). The stem cell-derived beta cells showed great potential as substitute sources of transplanted pancreatic islet cells. However, the current efficiency of stem cell differentiation still cannot match the requirements for clinical transplantation. Here, we report that microvesicles (MVs) from insulin-producing INS-1 cells could induce mesenchymal stem cell (MSC) differentiation into pancreatic beta-like cells. The combination of MVs with small molecules, nicotinamide and insulin-transferrin-selenium (ITS), dramatically improved the efficiency of MSC differentiation. Notably, the function of MVs in MSC differentiation requires their entry into MSCs through giant pinocytosis. The MVs-treated or MVs combined with small molecules-treated MSCs show pancreatic beta-like cell morphology and response to glucose stimulation in insulin secretion. Using high throughput small RNA-sequencing, we found that MVs induced MSC differentiation into the beta-like cells through miR-181a-5p/150-5p. Together, our findings reveal the role of MVs or the MV-enriched miR-181a-5p/150-5p as a class of biocompatible reagents to differentiate MSCs into functional beta-like cells and demonstrate that the combined usage of MVs or miR-181a-5p/150-5p with small molecules can potentially be used in making pancreatic islet cells for future clinical purposes.

Extracellular Vesicles Carrying RUNX3 Promote Differentiation of Dental Pulp Stem Cells

BACKGROUND

This study aims to clarify the mechanism underlying dental pulp cells-extracellular vesicles (DPC-EVs) carrying runt-related transcription factor 3 (RUNX3) in mediating odontogenic differentiation of dental pulp stem cells (DPSCs) with the involvement of miR-30a-5p-regulated NOTCH1.

METHODS

Extracellular vesicles (EVs) were isolated from human DPSCs, and identified using transmission electron microscopy, and nanoparticle tracking analysis. PBS, EVs, or EV inhibitor GW4869 was added to DPSCs for co-culture, whilst odontogenic differentiation was assessed in terms of ratio of mineralized nodules and expression odontoblast differentiation markers. Dual luciferase reporter gene assay and chromatin immunoprecipitation for binding relation among RUNX3, miR-30a-5p and NOTCH1were employed to evaluate their roles in odontogenic differentiation was determined. Animal experiment was established to confirm the effect of DPC-EVs-loaded RUNX3 on dental pulp.

RESULTS

In vitro finding demonstrated that EVs delivered RUNX3 to DPSCs, thereby activated miR-30a-5p expression and inhibited NOTCH1 expression, which was reversed by addition of GW4869. RUNX3 upregulation promoted miR-30a-5p while miR-30a-5p targeted and inhibited NOTCH1. Silencing of RUNX3 in EVs decreased expression of those differentiation markers, downregulated miR-30a-5p and upregulated NOTCH1.

CONCLUSION

DPSC-EVs can carry RUNX3 to the DPSCs, promote the transcription of miR-30a-5p, and then inhibit the expression of NOTCH1, and finally promote the odontogenic differentiation of DPSCs.

Natural medicine delivery from 3D printed bone substitutes

Unmet medical needs in treating critical-size bone defects have led to the development of numerous innovative bone tissue engineering implants. Although additive manufacturing allows flexible patient-specific treatments by modifying topological properties with various materials, the development of ideal bone implants that aid new tissue regeneration and reduce post-implantation bone disorders has been limited. Natural biomolecules are gaining the attention of the health industry due to their excellent safety profiles, providing equivalent or superior performances when compared to more expensive growth factors and synthetic drugs. Supplementing additive manufacturing with natural biomolecules enables the design of novel multifunctional bone implants that provide controlled biochemical delivery for bone tissue engineering applications. Controlled release of naturally derived biomolecules from a three-dimensional (3D) printed implant may improve implant-host tissue integration, new bone formation, bone healing, and blood vessel growth. The present review introduces us to the current progress and limitations of 3D printed bone implants with drug delivery capabilities, followed by an in-depth discussion on cutting-edge technologies for incorporating natural medicinal compounds embedded within the 3D printed scaffolds or on implant surfaces, highlighting their applications in several pre- and post-implantation bone-related disorders.

Extracellular Vesicles Derived from Auricular Chondrocytes Facilitate Cartilage Differentiation of Adipose-Derived Mesenchymal Stem Cells

PURPOSE

Adipose-derived mesenchymal stem cell (ADSC)-based therapies have been utilized for cartilage regeneration because of their multi-lineage differentiation ability. However, commonly used cartilage inducers such as the transforming growth factor beta-3 (TGF-β3) may be prone to cartilage dedifferentiation and hypertrophy. The directional differentiation of elastic cartilage is limited nowadays. Extracellular vesicles (EVs) have been reported to influence the specific differentiation of mesenchymal stem cells (MSCs) by reflecting the composition of the parental cells. However, the role of auricular chondrogenic-derived EVs (AC-EVs) in elastic chondrogenic differentiation of ADSCs has not yet been reported.

RESULTS

AC-EVs isolated from the external ears of swine exhibited a positive effect on cell proliferation and migration. Furthermore, AC-EVs efficiently promoted chondrogenic differentiation of ADSCs in pellet culture, as shown by the elevated levels of COL2A1, ACAN, and SOX-9 expression. Moreover, there was a significantly higher expression of elastin and a lower expression of the fibrotic marker COL1A1 in comparison with that achieved with TGF-β3. The staining results demonstrated that AC-EVs promoted the deposition of cartilage-specific matrix, which is in good concordance with the real-time polymerase chain reaction (RT-PCR) results.

CONCLUSIONS

Auricular chondrogenic-derived EVs are a crucial component in elastic chondrogenic differentiation and other biological behaviors of ADSCs, which may be a useful ingredient for cartilage tissue engineering and external ear reconstruction.

NO LEVEL ASSIGNED

This journal requires that authors 42 assign a level of evidence to each submission to which 43 Evidence-Based Medicine rankings are applicable. This 44 excludes Review Articles, Book Reviews, and manuscripts 45 that concern Basic Science, Animal Studies, Cadaver 46 Studies, and Experimental Studies. For a full description of 47 these Evidence-Based Medicine ratings, please refer to the 48 Table oôf Contents or the online Instructions to Authors 49 www.springer.com/00266 .

Advances in the regulation of adipogenesis and lipid metabolism by exosomal ncRNAs and their role in related metabolic diseases

Exosomes are membrane-bound extracellular vesicles released following the fusion of multivesicular bodies (MVBs) with the cell membrane. Exosomes transport diverse molecules, including proteins, lipids, DNA and RNA, and regulate distant intercellular communication. Noncoding RNA (ncRNAs) carried by exosomes regulate cell-cell communication in tissues, including adipose tissue. This review summarizes the action mechanisms of ncRNAs carried by exosomes on adipocyte differentiation and modulation of adipogenesis by exosomal ncRNAs. This study aims to provide valuable insights for developing novel therapeutics.

3D Printing of Microenvironment-Specific Bioinspired and Exosome-Reinforced Hydrogel Scaffolds for Efficient Cartilage and Subchondral Bone Regeneration

In clinical practice, repairing osteochondral defects presents a challenge due to the varying biological properties of articular cartilages and subchondral bones. Thus, elucidating how spatial microenvironment-specific biomimetic scaffolds can be used to simultaneously regenerate osteochondral tissue is an important research topic. Herein, a novel bioinspired double-network hydrogel scaffold produced via 3D printing with tissue-specific decellularized extracellular matrix (dECM) and human adipose mesenchymal stem cell (MSC)-derived exosomes is described. The bionic hydrogel scaffolds promote rat bone marrow MSC attachment, spread, migration, proliferation, and chondrogenic and osteogenic differentiation in vitro, as determined based on the sustained release of bioactive exosomes. Furthermore, the 3D-printed microenvironment-specific heterogeneous bilayer scaffolds efficiently accelerate the simultaneous regeneration of cartilage and subchondral bone tissues in a rat preclinical model. In conclusion, 3D dECM-based microenvironment-specific biomimetics encapsulated with bioactive exosomes can serve as a novel cell-free recipe for stem cell therapy when treating injured or degenerative joints. This strategy provides a promising platform for complex zonal tissue regeneration whilst holding attractive clinical translation potential.

An injectable, activated neutrophil-derived exosome mimetics/extracellular matrix hybrid hydrogel with antibacterial activity and wound healing promotion effect for diabetic wound therapy

Chronic diabetic wounds are primarily caused by infection, inflammation, and angiogenesis-related disorders. An ideal approach for treating chronic diabetic wounds is by combining anti-infection strategies, immune microenvironment regulation, and angiogenesis promotion. Vascular endothelial growth factor (VEGF) can promote the proliferation and migration of vascular endothelial cells, thereby promoting angiogenesis. However, the low stability and inability to target lesions limit its application. Polymorphonuclear neutrophil-derived exosomes (PMNExo) exhibit good delivery properties and can be used for the therapeutic delivery of VEGF. Furthermore, they retain the antibacterial ability of polymorphonuclear neutrophils (PMNs). Nonetheless, low PMNExo generation impedes its therapeutic applications. In this study, we prepared exosome mimetics (EM) from PMNs using the extrusion process; as a result, exosome yield significantly improved. To increase the residence of exosomes, an extracellular matrix (ECM) hydrogel, a thermosensitive material that can function as an in situ gel in vivo, was used as an exosome carrier. The active peptides in the ECM regulated the immune microenvironment of the wound. In summary, we loaded ECM with VEGF-encapsulated activated neutrophil exosome mimetics (aPMNEM) to develop VEGF-aPMNEM-ECM hybrid hydrogel for treating chronic wounds. The hydrogel accelerates the regeneration of chronic diabetic wounds. Our study provides a prospective therapy platform involving cytokines for treating different diseases.

[Characteristics and microRNA expression profile of exosomes derived from odontogenic dental pulp stem cells]

OBJECTIVE

To investigate the characteristics of exosomes derived from dental pulp stem cells (DPSCs) in the direction of odontogenic differentiation, to analyze the differences in microRNA expression profile between exosomes derived from undifferentiated and odontogenic DPSCs, and to analyze their possible signal transduction pathways.

METHODS

(1) DPSCs were cultured in α minimum Eagle' s medium (α-MEM), and odontogenic DPSCs were cultured in odontogenic differentiation medium for 21 days, using alizarin red staining and alkaline phosphatase staining to identify the odontogenic differentiation. Exosomes from the cell supernatant were isolated respectively, named as dental pulp stem cells-exosomes (DPSCs-Exo) and dental pulp stem cells-odontogenic-exosomes (DPSCs-OD-Exo). The exosomes were identified by transmission electron microscopy, nanoparticle tracking analysis and Western blot. (2) The microRNA expression profiles of DPSCs-Exo and DPSCs-OD-Exo were investigated by microRNA microarray. To validate the result of the microRNA microarray, real-time quantitative polymerase chain reaction (real-time PCR) assay was applied on 3 most significantly differential expressed microRNA. Pathway analysis was taken to detect enriched pathways associated with the predicted target genes of microRNA.

RESULTS

(1) The DPSCs were isolated and cultured in vitro showed typical fibroblast-like morphology. The odontogenic differentiated DPSCs were spindle-shaped, polygonal, and uniform in size. Odontogenic differentiation group showed a large number of dark deposits in alizarin red staining and the cells were darkly stained in alkaline phosphatase staining, while the cells in normal culture medium group did not show obvious dyeing. The DPSCs-Exo and DPSCs-OD-Exo had the same morphology, both showed bilayer membrane and cup-shape. The peak sizes of DPSCs-Exo and DPSCs-OD-Exo were (114.67±9.07) nm and (134.00±8.54) nm, respectively. The difference between the two was statistically significant. DPSCs-Exo and DPSCs-OD-Exo both expressed the markers of exosomes, tumor susceptibility gene (TSG)101 and CD63. (2) microRNA microarray results showed that the expression profiles of DPSCs-Exo and DPSCs-OD-Exo were different. Nineteen increased by more than two times, and one decreased by 64%. Real-time PCR results showed that the expression levels of microRNA-1246, microRNA-1246-100-5p and microRNA-1246-494-3p in DPSCs-OD-Exo were significantly up-regulated. The difference was statistically significant. microRNA target prediction database and gene signaling pathway database were used to analyze differentially expressed microRNA, and it was predicted that differentially expressed microRNA could target axis inhibition protein 2(AXIN2) gene and Wnt/β-catenin signaling pathway.

CONCLUSION

DPSCs-OD-Exo and DPSCs-Exo had differences in their microRNA expression profile. Those differentially expressed microRNA may be involved in the regulation of DPSCs odontogenic differentiation.

Engineering a Pro-Osteogenic Secretome through the Transient Silencing of the Gene Encoding Secreted Frizzled Related Protein 1

The evidence sustaining the regenerative properties of mesenchymal stem cells' (MSCs) secretome has prompted a paradigm change, where MSCs have shifted from being considered direct contributors to tissue regeneration toward being seen as cell factories for producing biotech medicines. We have previously designed a method to prime MSCs towards osteogenic differentiation by silencing the Wnt/β-Catenin inhibitor Sfpr1. This approach produces a significant increase in bone formation in osteoporotic mice. In this current work, we set to investigate the contribution of the secretome from the MSCs where Sfrp1 has been silenced, to the positive effect seen on bone regeneration in vivo. The conditioned media (CM) of the murine MSCs line C3H10T1/2, where Sfrp1 has been transiently silenced (CM-Sfrp1), was found to induce, in vitro, an increase in the osteogenic differentiation of this same cell line, as well as a decrease of the expression of the Wnt inhibitor Dkk1 in murine osteocytes ex vivo. A reduction in the RANKL/OPG ratio was also detected ex vivo, suggesting a negative effect of CM-Sfrp1 on osteoclastogenesis. Moreover, this CM significantly increases the mineralization of human primary MSCs isolated from osteoportotic patients in vitro. Proteomic analysis identified enrichment of proteins involved in osteogenesis within the soluble and vesicular fractions of this secretome. Altogether, we demonstrate the pro-osteogenic potential of the secretome of MSCs primmed in this fashion, suggesting that this is a valid approach to enhance the osteo-regenerative properties of MSCs' secretome.

Stimulating factors for regulation of osteogenic and chondrogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs), distributed in many tissues in the human body, are multipotent cells capable of differentiating in specific directions. It is usually considered that the differentiation process of MSCs depends on specialized external stimulating factors, including cell signaling pathways, cytokines, and other physical stimuli. Recent findings have revealed other underrated roles in the differentiation process of MSCs, such as material morphology and exosomes. Although relevant achievements have substantially advanced the applicability of MSCs, some of these regulatory mechanisms still need to be better understood. Moreover, limitations such as long-term survival in vivo hinder the clinical application of MSCs therapy. This review article summarizes current knowledge regarding the differentiation patterns of MSCs under specific stimulating factors.

Combination of natural scaffolds and conditional medium to induce the differentiation of adipose-derived mesenchymal stem cells into keratocyte-like cells and its safety evaluation in the animal cornea

Keratocytes are the main cellular components of the corneal stroma. This cell is quiescent and cannot be cultured easily. The aim of this study was to investigate differentiate human adipose mesenchymal stem cells (hADSCs) into corneal keratocyte cells by combining natural scaffolds and conditioned medium (CM) and evaluating their safety in the rabbit's cornea. Keratocytes were cultured in an optimal culture medium and this medium was collected and kept as a CM. hADSCs were cultured on the decellularized human small incision lenticule extraction (SMILE) lenticule (SL), amniotic membrane (AM), and collagen-coated plates, and were exposed to keratocyte-CM (KCM) for 7, 14, and 21 days. Differentiation was evaluated using Real-time PCR and immunocytochemistry (ICC). hADSCs were cultured on the SL scaffolds and implanted in the corneal stroma of 8 New Zealand male rabbits. Rabbits were followed for 3 months and the safety was evaluated by clinical and histological variables. Real-time PCR results showed a significant increase in the expression of keratocyte-specific markers on the 21 day of differentiation compared to the control group. ICC also confirmed the induction of differentiation. Implantation of SLs containing differentiated cells in the cornea of animals showed no serious complications including neovascularization, corneal opacity, inflammation, or signs of tissue rejection. Furthermore, the evaluation of the presence of keratocyte-like cells after three months in the rabbit stroma was confirmed by Real-time PCR and immunohistochemistry (IHC) analysis. Our results showed that combination of combination of corneal extracellular matrix and KCM can induced keratocytes differentiation of hADSC and can be introduced as a alternative method to supply the required keratocytes in corneal tissue engineering.

Differential Expression of Non-Coding RNAs in Stem Cell Development and Therapeutics of Bone Disorders

Stem cells' self-renewal and multi-lineage differentiation are regulated by a complex network consisting of signaling factors, chromatin regulators, transcription factors, and non-coding RNAs (ncRNAs). Diverse role of ncRNAs in stem cell development and maintenance of bone homeostasis have been discovered recently. The ncRNAs, such as long non-coding RNAs, micro RNAs, circular RNAs, small interfering RNA, Piwi-interacting RNAs, etc., are not translated into proteins but act as essential epigenetic regulators in stem cells' self-renewal and differentiation. Different signaling pathways are monitored efficiently by the differential expression of ncRNAs, which function as regulatory elements in determining the fate of stem cells. In addition, several species of ncRNAs could serve as potential molecular biomarkers in early diagnosis of bone diseases, including osteoporosis, osteoarthritis, and bone cancers, ultimately leading to the development of new therapeutic strategies. This review aims to explore the specific roles of ncRNAs and their effective molecular mechanisms in the growth and development of stem cells, and in the regulation of osteoblast and osteoclast activities. Furthermore, we focus on and explore the association of altered ncRNA expression with stem cells and bone turnover.

Modulating osteoclasts with nanoparticles: A path for osteoporosis management?

Osteoclasts are the cells responsible for the bone resorption process during bone remodeling. In a healthy situation, this process results from an equilibrium between new matrix formation by osteoblast and matrix resorption by osteoclast. Osteoporosis (OP) is a systemic bone disease characterized by a decreased bone mass density and alterations in bone microarchitecture, increasing fracture predisposition. Despite the variety of available therapies for OP management there is a growing gap in its treatment associated to the low patients´ adherence owing to concerns related with long-term efficacy or safety. This makes the development of new and safe treatments necessary. Among the newly developed strategies, the use of synthetic and natural nanoparticles to modulate osteoclasts differentiation, activity, apoptosis or crosstalk with osteoblasts have arisen. Synthetic nanoparticles exert their therapeutic effect either by loading antiresorptive drugs or including molecules for osteoclasts gene regulation. Moreover, this control over osteoclasts can be improved by their targeting to bone extracellular matrix or osteoclast membranes. Furthermore, natural nanoparticles, also known as extracellular vesicles, have been identified to play a key role in bone homeostasis. Consequently, these systems have been widely studied to control osteoblasts and osteoclasts under variable environments. Additionally, the ability to bioengineer extracellular vesicles has allowed to obtain biomimetic systems with desirable characteristics as drug carriers for osteoclasts. The analyzed information reveals the possibility of modulating osteoclasts by different mechanisms through nanoparticles decreasing bone resorption. These findings suggest that controlling osteoclast activity using nanoparticles has the potential to improve osteoporosis management. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

The Emerging Biological Functions of Exosomes from Dental Tissue-Derived Mesenchymal Stem Cells

Exosomes are one kind of small-cell extracellular membranous vesicles that can regulate intercellular communication and give rise to mediating the biological behaviors of cells, involving in tissue formation, repair, the modulation of inflammation, and nerve regeneration. The abundant kinds of cells can secret exosomes, among them, mesenchymal stem cells (MSCs) are very perfect cells for mass production of exosomes. Dental tissue-derived mesenchymal stem cells (DT-MSCs), including dental pulp stem cells, stem cells from exfoliated deciduous teeth, stem cells from apical papilla, stem cells from human periodontal ligament (PDLSCs), gingiva-derived mesenchymal stem cells, dental follicle stem cells, tooth germ stem cells, and alveolar bone-derived mesenchymal stem cells, are now known as a potent tool in the area of cell regeneration and therapy, more importantly, DT-MSCs can also release numerous types of exosomes, participating in the biological functions of cells. Hence, we briefly depict the characteristics of exosomes, give a detailed description of the biological functions and clinical application in some respects of exosomes from DT-MSCs through systematically reviewing the latest evidence, and provide a rationale for their use as tools for potential application in tissue engineering.

CEBPB upregulates P4HA2 to promote the malignant biological behavior in IDH1 wildtype glioma

Temozolomide (TMZ), the primary drug for glioma treatment, has limited treatment efficacy. Additionally, considerable evidence shows that isocitrate dehydrogenase 1 mutation-type (IDH1 mut) gliomas have a better response to TMZ than isocitrate dehydrogenase 1 wildtype (IDH1 wt) gliomas. Here, we aimed to identify potential mechanisms underlying this phenotype. Herein, the Cancer Genome Atlas bioinformatic data and 30 clinical samples from patients were analyzed to reveal the expression level of cytosine-cytosine-adenosine-adenosine-thymidine (CCAAT) Enhancer Binding Protein Beta (CEBPB) and prolyl 4-hydroxylase subunit alpha 2 (P4HA2) in gliomas. Next, cellular and animal experiments, including cell proliferation, colony formation, transwell, CCK-8, and xenograft assays, were performed to explore the tumor-promoting effects of P4HA2 and CEBPB. Then, chromatin immunoprecipitation (ChIP) assays were used to confirm the regulatory relationships between them. Finally, a co-immunoprecipitation (Co-IP) assay was performed to confirm the effect of IDH1-132H to CEBPB proteins. We found that CEBPB and P4HA2 expression was significantly upregulated in IDH1 wt gliomas and associated with poor prognosis. CEBPB knockdown inhibited the proliferation, migration, invasion, and temozolomide resistance of glioma cells and hindered the growth of glioma xenograft tumors. CEBPE, as a transcription factor, exerted its function by transcriptionally upregulating P4HA2 expression in glioma cells. Importantly, CEBPB is prone to ubiquitin-proteasomal degradation in IDH1 R132H glioma cells. We also demonstrated that both genes are related to collagen synthesis, as confirmed by in vivo experiments. Thus, CEBPE promotes proliferation and TMZ resistance by inducing P4HA2 expression in glioma cells and offers a potential therapeutic target for glioma treatment.

Titanium dioxide nanoparticles affect osteoblast-derived exosome cargos and impair osteogenic differentiation of human mesenchymal stem cells

Titanium (Ti) and its alloys are the most widely used metallic biomaterials in total joint replacement; however, increasing evidence supports the degradation of its surface due to corrosion and wear processes releasing debris (ions, and micro and nanoparticles) and contribute to particle-induced osteolysis and implant loosening. Cell-to-cell communication involving several cell types is one of the major biological processes occurring during bone healing and regeneration at the implant-bone interface. In addition to the internal response of cells to the uptake and intracellular localization of wear debris, a red flag is the ability of titanium dioxide nanoparticles (mimicking wear debris) to alter cellular communication with the tissue background, disturbing the balance between osseous tissue integrity and bone regenerative processes. This study aims to understand whether titanium dioxide nanoparticles (TiO₂ NPs) alter osteoblast-derived exosome (Exo) biogenesis and whether exosomal protein cargos affect the communication of osteoblasts with human mesenchymal stem/stromal cells (HMSCs). Osteoblasts are derived from mesenchymal stem cells coexisting in the bone microenvironment during development and remodelling. We observed that TiO₂ NPs stimulate immature osteoblast- and mature osteoblast-derived Exo secretion that present a distinct proteomic cargo. Functional tests confirmed that Exos derived from both osteoblasts decrease the osteogenic differentiation of HMSCs. These findings are clinically relevant since wear debris alter extracellular communication in the bone periprosthetic niche, contributing to particle-induced osteolysis and consequent prosthetic joint failure.

Micro RNA based MSC EV engineering: Targeting the BMP2 cascade for bone repair

Mesenchymal stem cell derived extracellular vesicles (MSC EVs) possess excellent immunomodulatory and therapeutic properties. While beneficial, from a translational perspective, extracellular vesicles with consistent functionality and target specificity are required to achieve the goals of precision medicine and tissue engineering. Prior research has identified that the miRNA composition of mesenchymal stem cell derived extracellular vesicles contributes significantly towards extracellular vesicles functionality. In this study, we hypothesized that mesenchymal stem cell derived extracellular vesicle functionality can be rendered pathway-specific using a miRNA-based extracellular vesicles engineering approach. To test this hypothesis, we utilized bone repair as a model system and the BMP2 signaling cascade as the targeted pathway. We engineered mesenchymal stem cell extracellular vesicles to possess increased levels of miR-424, a potentiator of the BMP2 signaling cascade. We evaluated the physical and functional characteristics of these extracellular vesicles and their enhanced ability to trigger the osteogenic differentiation of naïve mesenchymal stem cell in vitro and facilitate bone repair in vivo. Results indicated that the engineered extracellular vesicles retained their extracellular vesicles characteristics and endocytic functionality and demonstrated enhanced osteoinductive function by activating SMAD1/5/8 phosphorylation and mesenchymal stem cell differentiation in vitro and enhanced bone repair in vivo. Furthermore, the inherent immunomodulatory properties of the mesenchymal stem cell derived extracellular vesicles remained unaltered. These results serve as a proof-of-concept for miRNA-based extracellular vesicles engineering approaches for regenerative medicine applications.

Dental Pulp Stem Cells (DPSCs) and Tissue Regeneration: Mechanisms Mediated by Direct, Paracrine, or Autocrine Effects

Among mesenchymal stem cells, dental pulp stem cells (DPSCs) were discovered most recently [...].

The potential therapeutic role of extracellular vesicles in critical-size bone defects: Spring of cell-free regenerative medicine is coming

In recent years, the incidence of critical-size bone defects has significantly increased. Critical-size bone defects seriously affect patients' motor functions and quality of life and increase the need for additional clinical treatments. Bone tissue engineering (BTE) has made great progress in repairing critical-size bone defects. As one of the main components of bone tissue engineering, stem cell-based therapy is considered a potential effective strategy to regenerate bone tissues. However, there are some disadvantages including phenotypic changes, immune rejection, potential tumorigenicity, low homing efficiency and cell survival rate that restrict its wider clinical applications. Evidence has shown that the positive biological effects of stem cells on tissue repair are largely mediated through paracrine action by nanostructured extracellular vesicles (EVs), which may overcome the limitations of traditional stem cell-based treatments. In addition to stem cell-derived extracellular vesicles, the potential therapeutic roles of nonstem cell-derived extracellular vesicles in critical-size bone defect repair have also attracted attention from scholars in recent years. Currently, the development of extracellular vesicles-mediated cell-free regenerative medicine is still in the preliminary stage, and the specific mechanisms remain elusive. Herein, the authors first review the research progress and possible mechanisms of extracellular vesicles combined with bone tissue engineering scaffolds to promote bone regeneration via bioactive molecules. Engineering modified extracellular vesicles is an emerging component of bone tissue engineering and its main progression and clinical applications will be discussed. Finally, future perspectives and challenges of developing extracellular vesicle-based regenerative medicine will be given. This review may provide a theoretical basis for the future development of extracellular vesicle-based biomedicine and provide clinical references for promoting the repair of critical-size bone defects.

Understanding the interplay of membrane trafficking, cell surface mechanics, and stem cell differentiation

Stem cells can generate a diversity of cell types during development, regeneration and adult tissue homeostasis. Differentiation changes not only the cell fate in terms of gene expression but also the physical properties and functions of cells, e.g. the secretory activity, cell shape, or mechanics. Conversely, these activities and properties can also regulate differentiation itself. Membrane trafficking is known to modulate signal transduction and thus has the potential to control stem cell differentiation. On the other hand, membrane trafficking, particularly from and to the plasma membrane, depends on the mechanical properties of the cell surface such as tension within the plasma membrane or the cortex. Indeed, recent findings demonstrate that cell surface mechanics can also control cell fate. Here, we review the bidirectional relationships between these three fundamental cellular functions, i.e. membrane trafficking, cell surface mechanics, and stem cell differentiation. Furthermore, we discuss commonly used methods in each field and how combining them with new tools will enhance our understanding of their interplay. Understanding how membrane trafficking and cell surface mechanics can guide stem cell fate holds great potential as these concepts could be exploited for directed differentiation of stem cells for the fields of tissue engineering and regenerative medicine.

M1 Microglia-derived Exosomes Promote Activation of Resting Microglia and Amplifies Proangiogenic Effects through Irf1/miR-155-5p/Socs1 Axis in the Retina

Activation of microglia plays a key role in the development of neovascular retinal diseases. Therefore, it is essential to reveal its pathophysiological and molecular mechanisms to interfere with disease progression. Here a publicly available single-cell RNA sequencing dataset is used to identify that intercellular communications from M1 microglia toward M0 microglia are increased in the retinal angiogenesis model via exosomes. Moreover, the results both in vitro and in vivo demonstrate that M1 microglia-derived exosomes promote the activation and enhance the proangiogenic ability of resting microglia. Based on miRNA sequencing of exosomes combined with gene interference, further results show that activated microglia-derived exosomes promoted microglial activation by transmitting polarized signals to M0 microglia via miR-155-5p. Subsequently, miR-155-5p suppresses Socs1 and activates the NFκB pathway, which ultimately causes the inflammatory cascade and amplifies the proangiogenic effect. In addition, upregulated Irf1 drives the expression of miR-155-5p in activated microglia, thus leading to an increase in the tendency of miR-155-5p to be encapsulated by exosomes. Thus, this study elucidates the critical role of intercellular communication among various types of microglia in the complex retinal microenvironment during angiogenesis, and contributes to the novel, targeted, and potential therapeutic strategies for clinical retinal neovascularization.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: The Novel Therapeutic Option for Regenerative Dentistry

Dental mesenchymal stem cells (MSCs) are characterized by unlimited self-renewal ability and high multidirectional differentiation potential. Since dental MSCs can be easily isolated and exhibit a high capability to differentiate into odontogenic cells, they are considered as attractive therapeutic agents in regenerative dentistry. Recently, MSC-derived extracellular vesicles (MSC-EVs) have attracted widespread attention as carriers for cell-free therapy due to their potential functions. Many studies have shown that MSC-EVs can mediate microenvironment at tissue damage site, and coordinate the regeneration process. Additionally, MSC-EVs can mediate intercellular communication, thus affecting the phenotypes and functions of recipient cells. In this review, we mainly summarized the types of MSCs that could be potentially applied in regenerative dentistry, the possible molecular cargos of MSC-EVs, and the major effects of MSC-EVs on the therapeutic induction of osteogenic differentiation.

Exosomes: A new option for osteoporosis treatment

Osteoporosis is a systemic bone disease characterized by reduced bone mass and destruction of bone microarchitecture, leading to increased bone fragility and susceptibility to fracture. However, the pathogenesis and molecular mechanisms of this disease remain unclear. Extracellular vesicles, structures originating from the plasma membrane and ranging from 30 nm to 5 µm in diameter, play an important role in intercellular communication in the bone microenvironment. Exosomes are extracellular vesicles that deliver cargo molecules, including endogenous proteins, lipids and nucleic acids. These cargo molecules are encapsulated in a lipid bilayer and internalized by target cells through receptor-ligand interactions or lipid membrane fusion. With the advancement of exosome research, exosome therapy for osteoporosis is fast becoming a research hotspot for researchers. This review aims to discuss the role of exosomes in the pathogenesis of osteoporosis. In addition, emerging diagnostic and therapeutic properties of exosomes are described to highlight the potential role of exosomes in osteoporosis.

Morinda officinalis polysaccharide enable suppression of osteoclastic differentiation by exosomes derived from rat mesenchymal stem cells

CONTEXT

Morinda officinalis F.C. How. (MO) (Rubiaceae) can strengthen bone function.

OBJECTIVE

To examine the functional mechanism and effect of MO polysaccharides (MOPs) in rats with glucocorticoid-induced osteoporosis (GIOP).

MATERIALS AND METHODS

Rats with GIOP were treated with 5, 15 or 45 mL/kg of MOP [n = 15 for each dose, intraperitoneal (i.p.) injection every other day for 8 weeks]. The body weight of rats and histomorphology of bone tissues were examined. Bone marrow mesenchymal stem cells (BMSCs)-derived exosomes (Exo) were collected and identified. Bone marrow-derived macrophages (BMMs) were induced to differentiate into osteoclasts and treated with BMSC-Exo for in vitro studies.

RESULTS

MOP reduced the body weight (5, 15, or 45 mg/kg MOP vs. phosphate-buffered saline: 8%, 15% and 25%, p < 0.01), elevated the bone volume to tissue volume (BV/TV), mean trabecular thickness (Tb.Th), mean trabecular number (Tb.N) and mean connectivity density (Conn.D) (40-86%, p < 0.01), decreased the mean trabecular separation/spacing (Tb.Sp) (22-37%, p < 0.01), increased the cortical bone continuity (35-90%, p < 0.01) and elevated RUNX family transcription factor 2 and RANK levels (5-12%, p < 0.01), but suppressed matrix metallopeptidase 9 and cathepsin K levels (9-20%, p < 0.01) in femur tissues. BMSC-Exo from MOP-treated rats (MOP-Exo) suppressed osteoclastic differentiation and proliferation of BMMs. The downregulation of microRNA-101-3p (miR-101-3p) or the upregulation of prostaglandin-endoperoxide synthase 2 (PTGS2) blocked the functions of MOP-Exo.

DISCUSSION AND CONCLUSIONS

MOP inhibits osteoclastic differentiation and could potentially be used for osteoporosis management. This suppression may be enhanced by the upregulation of miR-101-3p or the inhibition of PTGS2.

Exosome mediated biological functions within skeletal microenvironment

Exosomes are membranous lipid vesicles fused with intracellular multicellular bodies that are released into the extracellular environment. They contain bioactive substances, including proteins, RNAs, lipids, and cytokine receptors. Exosomes in the skeletal microenvironment are derived from a variety of cells such as bone marrow mesenchymal stem cells (BMSCs), osteoblasts, osteoclasts, and osteocytes. Their biological function is key in paracrine or endocrine signaling. Exosomes play a role in bone remodeling by regulating cell proliferation and differentiation. Genetic engineering technology combined with exosome-based drug delivery can therapy bone metabolic diseases. In this review, we summarized the pathways of exosomes derived from different skeletal cells (i.e., BMSCs, osteoblasts, osteocytes, and osteoclasts) regulate the skeletal microenvironment through proteins, mRNAs, and non-coding RNAs. By exploring the role of exosomes in the skeletal microenvironment, we provide a theoretical basis for the clinical treatment of bone-related metabolic diseases, which may lay the foundation to improve bone tumor microenvironments, alleviate drug resistance in patients.

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.

Exosomes Derived from Dental Pulp Stem Cells Show Different Angiogenic and Osteogenic Properties in Relation to the Age of the Donor

Craniofacial tissue reconstruction still represents a challenge in regenerative medicine. Mesenchymal stem cell (MSC)-based tissue engineering strategies have been introduced to enhance bone tissue repair. However, the risk of related complications is limiting their usage. To overcome these drawbacks, exosomes (EXOs) derived from MSCs have been recently proposed as a cell-free alternative to MSCs to direct tissue regeneration. It was hypothesized that there is a correlation between the biological properties of exosomes derived from the dental pulp and the age of the donor. The aim of the study was to investigate the effect of EXOs derived from dental pulp stem cells of permanent teeth (old donor group) or exfoliated deciduous teeth (young donor group) on MSCs cultured in vitro. Proliferation potential was evaluated by doubling time, and commitment ability by gene expression and biochemical quantification for tissue-specific factors. Results showed a well-defined proliferative influence for the younger donor aged group. Similarly, a higher commitment ability was detected in the young group. In conclusion, EXOs could be employed to promote bone regeneration, likely playing an important role in neo-angiogenesis in early healing phases.

Bone Cell Exosomes and Emerging Strategies in Bone Engineering

Bone tissue remodeling is a highly regulated process balancing bone formation and resorption through complex cellular crosstalk between resident bone and microenvironment cells. This cellular communication is mediated by direct cell and cell–matrix contact, autocrine, endocrine, and paracrine receptor mediated mechanisms such as local soluble signaling molecules and extracellular vesicles including nanometer sized exosomes. An impairment in this balanced process leads to development of pathological conditions. Bone tissue engineering is an emerging interdisciplinary field with potential to address bone defects and disorders by synthesizing three-dimensional bone substitutes embedded with cells for clinical implantation. However, current cell-based therapeutic approaches have faced hurdles due to safety and ethical concerns, challenging their clinical translation. Recent studies on exosome-regulated bone homeostasis and regeneration have gained interest as prospective cell free therapy in conjugation with tissue engineered bone grafts. However, exosome research is still in its nascent stages of bone tissue engineering. In this review, we specifically describe the role of exosomes secreted by cells within bone microenvironment such as osteoblasts, osteocytes, osteoclasts, mesenchymal stem cell cells, immune cells, endothelial cells, and even tumor cells during bone homeostasis and crosstalk. We also review exosome-based osteoinductive functionalization strategies for various bone-based biomaterials such as ceramics, polymers, and metals in bone tissue engineering. We further highlight biomaterials as carrier agents for exosome delivery to bone defect sites and, finally, the influence of various biomaterials in modulation of cell exosome secretome.

Decellularized Dental Pulp, Extracellular Vesicles, and 5-Azacytidine: A New Tool for Endodontic Regeneration

Dental pulp is a major component of the dental body that serves to maintain the tooth life and function. The aim of the present work was to develop a system that functions as a growth-permissive microenvironment for dental pulp regeneration using a decellularized dental pulp (DDP) matrix, 5-Aza-2′-deoxycytidine (5-Aza), and Extracellular Vesicles (EVs) derived from human Dental Pulp Stem Cells (hDPSCs). Human dental pulps extracted from healthy teeth, scheduled to be removed for orthodontic purpose, were decellularized and then recellularized with hDPSCs. The hDPSCs were seeded on DDP and maintained under different culture conditions: basal medium (CTRL), EVs, 5-Aza, and EVs+-5-Aza. Immunofluorescence staining and Western blot analyses were performed to evaluate the proteins’ expression related to dentinogenesis, such as ALP, RUNX2, COL1A1, Vinculin, DMP1, and DSPP. Protein contents found in the DDP recellularized with hDPSCs were highly expressed in samples co-treated with EVs and 5-Aza compared to other culture conditions. This study developed a DDP matrix loaded by hDPSCs in co-treatment with EVs, which might enhance the dentinogenic differentiation with a high potentiality for endodontic regeneration.

Secretome of Stem Cells: Roles of Extracellular Vesicles in Diseases, Stemness, Differentiation, and Reprogramming

Increasing evidence suggests that stem cells or stem cell-derived cells may contribute to tissue repair, not only by replacing lost tissue but also by delivering complex sets of secretory molecules, called secretomes, into host injured tissues. In recent years, extracellular vesicles (EVs) have gained much attention for their diverse and important roles in a wide range of pathophysiological processes. EVs are released from most types of cells and mediates cell-cell communication by activating receptors on target cells or by being taken up by recipient cells. EVs, including microvesicles and exosomes, encapsulate and carry proteins, nucleic acids, and lipids in the lumen and on the cell surface. Thus, EV-mediated intercellular communication has been extensively studied across various biological processes. While a number of investigations has been conducted in different tissues and body fluids, the field lacks a systematic review on stem cell-derived EVs, especially regarding their roles in stemness and differentiation. Here, we provide an overview of the pathophysiological roles of EVs and summarize recent findings focusing on EVs released from various types of stem cells. We also highlight emerging evidence for the potential implication of EVs in self-renewal, differentiation, and reprograming and discuss the benefits and limitations in translational approaches.

Intercellular and interorgan crosstalk through adipocyte extracellular vesicles

Functional adipose tissue is essential for homeostatic maintenance of systemic metabolism. As such, adipose tissue dysfunction, like that seen in the obese state, directly contributes to system-wide pathological metabolism, leading to the development of type 2 diabetes and other obesity-associated comorbidities. In addition to the storage function of adipocytes, they also secrete numerous factors that robustly regulate metabolism-related pathways throughout the body. Many of these factors, in addition to other signaling proteins, RNA species and lipids, are found in extracellular vesicles (EVs) released from adipocytes. EVs are vesicles with a lipid bilayer, known to carry signaling proteins and lipids, mRNAs and miRNAs. Because of this diverse cargo, EVs can have robust and pleotropic signaling effects depending on the receiving target cells. We are only now starting to understand how adipocyte EVs can modulate metabolism within adipose tissue and beyond. Here, we highlight the current literature that demonstrates EV-mediated crosstalk between adipocytes and other tissues or distal cells. We become increasingly aware of the importance of these adipocyte-derived EV signals that establish a so far underappreciated endocrine system. Adipocyte EVs offer a new avenue for pharmacological manipulation of metabolism to treat obesity-related disease.

Potential Effects of Exosomes and Their MicroRNA Carrier on Osteoporosis

Osteoporosis is a typical localized or systemic skeletal disease in the clinic, mainly characterized by the weakness of bone formation and the increase of bone resorption, resulting in the decrease of bone mineral density (BMD), and frequently occurs in postmenopausal women. With the growth of the aging population, the risk of osteoporosis or even osteoporotic fracture brings great economic pressure on society and families. Although anti-osteoporosis drugs have been developed, there are still some side effects in the treatment group. Hence, that is a compelling need for more reasonable therapeutic strategies. Exosomes are nanosized extracellular vesicles (EVs), secreted by virtually all types of cells in vivo, which play an important role in intercellular communication. Compared with conventional drugs and stem cells transplantation therapy, exosomes have apparent advantages of lower toxicity and immunogenicity. Exosomes contain many functional molecules, such as proteins, lipids, mRNAs, microRNAs (miRNAs), which can be transferred into recipient cells to regulate a series of signaling pathways and influence physiological and pathological behavior. In this review, we briefly summarize the current knowledge of exosomes and the therapeutic potential of exosomal miRNAs derived from mesenchymal stem cells (MSCs), osteoblasts, osteoclasts, and macrophages in osteoporosis. Finally, a prospect of new treatment strategies for osteoporosis using new biomaterial scaffolds combined with exosomes is also given.

Prospect on the application of mesenchymal stem cell-derived extracellular vesicles in the regeneration of dental and maxillofacial tissues

Extracellular vesicles (EVs) are the essential mediators of communication between different cells or tissues. EVs participate in the development, homeostasis, repair, and regeneration of tissues. Mesenchymal stem cells(MSCs) secrete a range of bioactive factors, which are important in MSC-mediated tissue regeneration. Great progress has been made in the research of EVs derived from MSCs (MSC-EVs) in the regeneration of dental and maxillofacial tissues. Emerging evidence confirmed that MSC-EVs can efficiently modulate the proliferation, differentiation, survival, and migration of stem or progenitor cells and stimulate the regeneration of the neurovascular system. MSC-EVs have been used in regenerating dental pulp, periodontium, jawbone, temporomandibular joint, and maxillofacial soft tissues. Having the advantages of low immunogenicity, versatile function, and suitability for large-scale production, EVs have excellent clinical application prospect. Along with investigations on molecular mechanisms of action and development of standard manufactory and testing systems, therapies u-sing MSC-EVs are promising strategies for regenerating dental and maxillofacial tissues.

Role of Exosomal Non-Coding RNAs in Bone-Related Diseases

Bone-related diseases seriously affect the lives of patients and carry a heavy economic burden on society. Treatment methods cannot meet the diverse clinical needs of affected patients. Exosomes participate in the occurrence and development of many diseases through intercellular communication, including bone-related diseases. Studies have shown that exosomes can take-up and “package” non-coding RNAs and “deliver” them to recipient cells, thereby regulating the function of recipient cells. The exosomal non-coding RNAs secreted by osteoblasts, osteoclasts, chondrocytes, and other cells are involved in the regulation of bone-related diseases by inhibiting osteoclasts, enhancing chondrocyte activity and promoting angiogenesis. Here, we summarize the role and therapeutic potential of exosomal non-coding RNAs in the bone-related diseases osteoporosis, osteoarthritis, and bone-fracture healing, and discuss the clinical application of exosomes in patients with bone-related diseases.

Enhancing extracellular vesicles for therapeutic treatment of arthritic joints

Extracellular vesicles are small membrane-derived packages of information that are released from virtually all cell types. These nano-packages contain regulatory material including proteins, lipids, mRNA and microRNA and are a key mechanism of paracellular communication within a given microenvironment. Encompassed with a lipid bilayer, these organelles have been attributed numerous roles in regulating both physiological and pathological functions. Herein, we describe the role of EVs in the context of Rheumatoid and Osteoarthritis and explore how they could be harnessed to treat inflammatory and degenerative joint conditions. These structures offer a promising therapeutic strategy for treating musculoskeletal diseases due to their bioactive content, stability, small size and intrinsic ability to enter the avascular cartilage, a notoriously challenging tissue to target. We also discuss how EVs can be manipulated to load therapeutic cargo or present additional targeting moieties to enhance their beneficial actions and tissue regenerative properties.

Functional Dental Pulp Regeneration: Basic Research and Clinical Translation

Pulpal and periapical diseases account for a large proportion of dental visits, the current treatments for which are root canal therapy (RCT) and pulp revascularisation. Despite the clinical signs of full recovery and histological reconstruction, true regeneration of pulp tissues is still far from being achieved. The goal of regenerative endodontics is to promote normal pulp function recovery in inflamed or necrotic teeth that would result in true regeneration of the pulpodentinal complex. Recently, rapid progress has been made related to tissue engineering-mediated pulp regeneration, which combines stem cells, biomaterials, and growth factors. Since the successful isolation and characterisation of dental pulp stem cells (DPSCs) and other applicable dental mesenchymal stem cells, basic research and preclinical exploration of stem cell-mediated functional pulp regeneration via cell transplantation and cell homing have received considerably more attention. Some of this effort has translated into clinical therapeutic applications, bringing a ground-breaking revolution and a new perspective to the endodontic field. In this article, we retrospectively examined the current treatment status and clinical goals of pulpal and periapical diseases and scrutinized biological studies of functional pulp regeneration with a focus on DPSCs, biomaterials, and growth factors. Then, we reviewed preclinical experiments based on various animal models and research strategies. Finally, we summarised the current challenges encountered in preclinical or clinical regenerative applications and suggested promising solutions to address these challenges to guide tissue engineering-mediated clinical translation in the future.

Extracellular vesicles for tissue repair and regeneration: Evidence, challenges and opportunities

Extracellular vesicles (EVs) are biological nanoparticles naturally secreted by cells, acting as delivery vehicles for molecular messages. During the last decade, EVs have been assigned multiple functions that have established their potential as therapeutic mediators for a variety of diseases and conditions. In this review paper, we report on the potential of EVs in tissue repair and regeneration. The regenerative properties that have been associated with EVs are explored, detailing the molecular cargo they carry that is capable of mediating such effects, the signaling cascades triggered in target cells and the functional outcome achieved. EV interactions and biodistribution in vivo that influence their regenerative effects are also described, particularly upon administration in combination with biomaterials. Finally, we review the progress that has been made for the successful implementation of EV regenerative therapies in a clinical setting.

Emerging Potential of Exosomes on Adipogenic Differentiation of Mesenchymal Stem Cells

The mesenchymal stem cells have multidirectional differentiation potential and can differentiate into adipocytes, osteoblasts, cartilage tissue, muscle cells and so on. The adipogenic differentiation of mesenchymal stem cells is of great significance for the construction of tissue-engineered fat and the treatment of soft tissue defects. Exosomes are nanoscale vesicles secreted by cells and widely exist in body fluids. They are mainly involved in cell communication processes and transferring cargo contents to recipient cells. In addition, exosomes can also promote tissue and organ regeneration. Recent studies have shown that various exosomes can influence the adipogenic differentiation of stem cells. In this review, the effects of exosomes on stem cell differentiation, especially on adipogenic differentiation, will be discussed, and the mechanisms and conclusions will be drawn. The main purpose of studying the role of these exosomes is to understand more comprehensively the influencing factors existing in the process of stem cell differentiation into adipocytes and provide a new idea in adipose tissue engineering research.

miR-212/132-Enriched Extracellular Vesicles Promote Differentiation of Induced Pluripotent Stem Cells Into Pancreatic Beta Cells

Pancreatic beta cell transplantation is the ideal method for treatment of type 1 diabetes mellitus (T1DM), and the generation of beta cells from induced pluripotent stem cells (iPSCs) of patients is a promising strategy. In this study, we improved a previous strategy to produce beta cells using extracellular vesicles (EVs) derived from mature beta cells and differentiated beta cells from iPSCs (i-Beta cells), which secreted insulin under glucose stimulation in vitro and ameliorated hyperglycemia in vivo. Mechanistic analyses revealed that EV-carried microRNA (miR)-212/132 (EV-miR-212/132) directly bound to the 3' UTR of FBW7 to prevent its translation and FBW7 combined with NGN3 to accelerate its proteasomal degradation. EV-miR-212/132 stabilized NGN3 expression to promote differentiation of endocrine cells from induced iPSCs. Moreover, NGN3 bound to PDX1 to enhance transcription of endogenous miR-212/132 and formed a positive regulatory circuit that maintained the functions of mature pancreatic beta cells.

CONCLUSION

This study describes a novel approach for beta cell production and supports the use of iPSCs for cell replacement therapy of T1DM.

3D Encapsulation and tethering of functionally engineered extracellular vesicles to hydrogels

Mesenchymal stem cell (MSC) derived extracellular vesicles (EVs) in their naïve and engineered forms have emerged as potential alternatives to stem cell therapy. While they have a defined therapeutic potential, the spatial and temporal control of their activity in vivo remains a challenge. The objective of this study was to devise a methodology to encapsulate EVs in 3D hydrogels for prolonged delivery. To achieve this, we have leveraged the MSC EV interactions with ECM proteins and their derivative peptides. Using osteoinductive functionally engineered EVs (FEEs) derived from MSCs, we show that FEEs bind to mimetic peptides from collagen (DGEA, GFPGER) and fibronectin (RGD). In in vitro experiments, photocrosslinkable alginate hydrogels containing RGD were able to encapsulate, tether and retain the FEEs over a period of 7 days while maintaining the structural integrity and osteoinductive functionality of the EVs. When employed in a calvarial defect model in vivo, alginate-RGD hydrogels containing the FEEs enhanced bone regeneration by a factor of 4 compared to controls lacking FEEs and by a factor of 2 compared to controls lacking the tethering peptide. These results show that EVs can be tethered to biomaterials to promote bone repair and the importance of prolonged delivery in vivo. Results also provide a prelude to the possible use of this technology for controlled delivery of EVs for other regenerative medicine applications. STATEMENT OF SIGNIFICANCE: The beneficial effects of human MSC (HMSC) therapy are attributable to paracrine effects of the HMSC derived EVs. While EV engineering has the potential to impact several fields of regenerative medicine, targeted delivery of the engineered EVs with spatial and temporal control is necessary to prevent off-target effects and enhance tissue specificity. Here, we have leveraged the interactions of MSC EVs with ECM proteins to develop a tethering system that can be utilized to prolong EV delivery in vivo while maintaining the structural and functional integrity of the EVs. Our work has provided a tunable platform for EV delivery that we envision can be formulated as an injectable material or a bulk hydrogel suitable for regenerative medicine applications.

The tissue origin effect of extracellular vesicles on cartilage and bone regeneration

Direct implantation of mesenchymal stem cells (MSCs) for cartilage and bone tissue engineering faces challenges, such as immune rejection and loss of cellular viability or functionality. As nanoscale natural particles, exosomes or small extracellular vesicles (EVs) of MSCs have potential to circumvent these problems. It is significant to investigate the impact of the tissue origin of MSCs on the therapeutic bioactivity of their corresponding EVs for cartilage and bone regeneration. Here, rat MSCs isolated from the adipose, bone marrow, and synovium are cultured to obtain their corresponding EVs (ADSC-EVs, BMSC-EVs, and SMSC-EVs, respectively). The ADSC-EVs stimulate the migration, proliferation, and chondrogenic and osteogenic differentiation of BMSCs in vitro as well as cartilage and bone regeneration in a mouse model more than the BMSC-EVs or SMSC-EVs. Proteomics analysis reveals that the tissue origin contributes to the distinct protein profiles among the three types of EVs, which induced cartilage and bone regenerative capacities by potential mechanisms of regulating signaling pathways including focal adhesion, ECM-receptor interaction, actin cytoskeleton, cAMP, and PI3K-Akt signaling pathways. Consequently, these findings provide insight that the adipose may be a superior candidate in EV-based nanomedicine for cartilage and bone regeneration. STATEMENT OF SIGNIFICANCE: Extracelluar vesicles (EVs) of mesenchymal stem cells (MSCs) have been considered as a promising approach in cartilage and bone tissue engineering. In this study, for the first time, we investigated the tissue origin effect of EVs on chondrogenesis and osteogenesis of MSCs in vitro and in vivo. The results demonstrated that EVs of adipose-derived MSCs showed the most efficiency. Meanwhile, protein proteomics revealed the potential mechanisms. We provide a novel evidence that the adipose is a superior reservoir in EV-based nanotechnologies and biomaterials for cartilage and bone regeneration.

Exosome-Derived Noncoding RNAs as a Promising Treatment of Bone Regeneration

The reconstruction of large bone defects remains a crucial challenge in orthopedic surgery. The current treatments including autologous and allogenic bone grafting and bioactive materials have their respective drawbacks. While mesenchymal stem cell (MSC) therapy may address these limitations, growing researches have demonstrated that the effectiveness of MSC therapy depends on paracrine factors, particularly exosomes. This aroused great focus on the exosome-based cell-free therapy in the treatment of bone defects. Exosomes can transfer various cargoes, and noncoding RNAs are the most widely studied cargo through which exosomes exert their ability of osteoinduction. Here, we review the research status of the exosome-derived noncoding RNAs in bone regeneration, the potential application of exosomes, and the existing challenges.

Human cardiomyocyte-derived exosomes induce cardiac gene expressions in mesenchymal stromal cells within 3D hyaluronic acid hydrogels and in dose-dependent manner

Accomplishing a reliable lineage-specific differentiation of stem cells is vital in tissue engineering applications, however, this need remained unmet. Extracellular nanovesicles (particularly exosomes) have previously been shown to have this potential owing to their rich biochemical content including proteins, nucleic acids and metabolites. In this work, the potential of human cardiomyocytes-derived exosomes to induce in vitro cardiac gene expressions in human mesenchymal stem cells (hMSCs) was evaluated. Cardiac exosomes (CExo) were integrated with hyaluronic acid (HA) hydrogel, which was functionalized with tyramine (HA-Tyr) to enable the development of 3D (three dimensional), robust and bioactive hybrid cell culture construct through oxidative coupling. In HA-Tyr/CExo 3D hybrid hydrogels, hMSCs exhibited good viability and proliferation behaviours. Real time quantitative polymerase chain reaction (RT-qPCR) results demonstrated that cells incubated within HA-Tyr/CExo expressed early cardiac progenitor cell markers (GATA4, Nkx2.5 and Tbx5), but not cTnT, which is expressed in the late stages of cardiac differentiation and development. The expressions of cardiac genes were remarkably increased with increasing CExo concentration, signifying a dose-dependent induction of hMSCs. This report, to some extent, explains the potential of tissue-specific exosomes to induce lineage-specific differentiation. However, the strategy requires further mechanistic explanations so that it can be utilized in translational medicine.