Comparison of the ability of exosomes and ectosomes derived from adipose-derived stromal cells to promote cartilage regeneration in a rat osteochondral defect model.

BACKGROUND: Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) offer promising prospects for stimulating cartilage regeneration. The different formation mechanisms suggest that exosomes and ectosomes possess different biological functions. However, little attention has been paid to the differential effects of EV subsets on cartilage regeneration. METHODS: Our study compared the effects of the two EVs isolated from adipose-derived MSCs (ASCs) on chondrocytes and bone marrow-derived MSCs (BMSCs) in vitro. Additionally, we loaded the two EVs into type I collagen hydrogels to optimize their application for the treatment of osteochondral defects in vivo. RESULTS: In vitro experiments demonstrate that ASC-derived exosomes (ASC-Exos) significantly promoted the proliferation and migration of both cells more effectively than ASC-derived ectosomes (ASC-Ectos). Furthermore, ASC-Exos facilitated a stronger differentiation of BMSCs into chondrogenic cells than ASC-Ectos, but both inhibited chondrocyte apoptosis to a similar extent. In the osteochondral defect model of rats, ASC-Exos promoted cartilage regeneration in situ better than ASC-Ectos. At 8 weeks, the hydrogel containing exosomes group (Gel + Exo group) had higher macroscopic and histological scores, a higher value of trabecular bone volume fraction (BV/TV), a lower value of trabecular thickness (Tb.Sp), and a better remodeling of extracellular matrix than the hydrogel containing ectosomes group (Gel + Ecto group). At 4 and 8 weeks, the expression of CD206 and Arginase-1 in the Gel + Exo group was significantly higher than that in the Gel + Ecto group. CONCLUSION: Our findings indicate that administering ASC-Exos may be a more effective EV strategy for cartilage regeneration than the administration of ASC-Ectos.

Advances in Hydrogels for Meniscus Tissue Engineering: A Focus on Biomaterials, Crosslinking, Therapeutic Additives.

Meniscus tissue engineering (MTE) has emerged as a promising strategy for meniscus repair and regeneration. As versatile platforms, hydrogels have gained significant attention in this field, as they possess tunable properties that allow them to mimic native extracellular matrices and provide a suitable microenvironment. Additionally, hydrogels can be minimally invasively injected and can be adjusted to match the shape of the implant site. They can conveniently and effectively deliver bioactive additives and demonstrate good compatibility with other functional materials. These inherent qualities have made hydrogel a promising candidate for therapeutic approaches in meniscus repair and regeneration. This article provides a comprehensive review of the advancements made in the research on hydrogel application for meniscus tissue engineering. Firstly, the biomaterials and crosslinking strategies used in the formation of hydrogels are summarized and analyzed. Subsequently, the role of therapeutic additives, including cells, growth factors, and other active products, in facilitating meniscus repair and regeneration is thoroughly discussed. Furthermore, we summarize the key issues for designing hydrogels used in MTE. Finally, we conclude with the current challenges encountered by hydrogel applications and suggest potential solutions for addressing these challenges in the field of MTE. We hope this review provides a resource for researchers and practitioners interested in this field, thereby facilitating the exploration of new design possibilities.

Self-adaptive pyroptosis-responsive nanoliposomes block pyroptosis in autoimmune inflammatory diseases.

Nanoliposomes have a broad range of applications in the treatment of autoimmune inflammatory diseases because of their ability to considerably enhance drug transport. For their clinical application, nanoliposomes must be able to realize on-demand release of drugs at disease sites to maximize drug-delivery efficacy and minimize side effects. Therefore, responsive drug-release strategies for inflammation treatment have been explored; however, no specific design has been realized for a responsive drug-delivery system based on pyroptosis-related inflammation. Herein, we report a pioneering strategy for self-adaptive pyroptosis-responsive liposomes (R8-cardiolipin-containing nanoliposomes encapsulating dimethyl fumarate, RC-NL@DMF) that precisely release encapsulated anti-pyroptotic drugs into pyroptotic cells. The activated key pyroptotic protein, the N-terminal domain of gasdermin E, selectively integrates with the cardiolipin of liposomes, thus forming pores for controlled drug release, pyroptosis, and inflammation inhibition. Therefore, RC-NL@DMF exhibited effective therapeutic efficacies to alleviate autoimmune inflammatory damages in zymosan-induced arthritis mice and dextran sulfate sodium-induced inflammatory bowel disease mice. Our novel approach holds great promise for self-adaptive pyroptosis-responsive on-demand drug delivery, suppressing pyroptosis and treating autoimmune inflammatory diseases.

Comparative Effects of Exosomes and Ectosomes Isolated From Adipose-Derived Mesenchymal Stem Cells on Achilles Tendinopathy in a Rat Model.

BACKGROUND: Extracellular vesicles derived from mesenchymal stem cells (MSC-EVs) have gained momentum as a treatment for tendinopathy. Multiple studies have demonstrated significant differences in cargo composition between the 2 subtypes of MSC-EVs (ie, exosomes and ectosomes), which may result in different therapeutic effects. However, the effects of the 2 EV subtypes on tendinopathy have not yet been compared. PURPOSE: To compare the effects of adipose stem cell-derived exosomes (ASC-Exos) and ectosomes (ASC-Ectos) on Achilles tendinopathy. STUDY DESIGN: Controlled laboratory study. METHODS: Rats were administered collagenase injections to generate a model of Achilles tendinopathy. A week later, 36 rats were randomly assigned to 3 groups. In each group, Achilles tendons were injected with equal volumes of ASC-Exos, ASC-Ectos, or saline (12 legs/group). The healing outcomes were evaluated by magnetic resonance imaging, histology, immunohistochemistry, transmission electron microscopy, and biomechanical testing at 3 and 5 weeks after collagenase injection. RESULTS: At 3 and 5 weeks, the ASC-Exo group had better histological scores (P = .0036 and P = .0276, respectively), a lower fibril density (P < .0001 and P = .0310, respectively), and a larger collagen diameter (P = .0052 and P < .0001, respectively) than the ASC-Ecto group. At 5 weeks, the expression of collagen type 1 and CD206 in the ASC-Exo group was significantly higher than that in the ASC-Ecto group (P = .0025 and P = .0010, respectively). Regarding biomechanical testing, the ASC-Exo group showed higher failure load (P = .0005), tensile stress (P < .0001), and elastic modulus (P < .0001) than the ASC-Ecto group. CONCLUSION: ASC-Exos had more beneficial effects on tendon repair than ASC-Ectos in a rat model of Achilles tendinopathy. CLINICAL RELEVANCE: Administration of ASC-EVs may have the potential to treat Achilles tendinopathy, and delivery of ASC-Exos could provide additional benefits. It is necessary to compare the healing responses caused by different EV subtypes to further understand their effects on tendinopathy and to aid clinical decision making.

A 3D-printed PRP-GelMA hydrogel promotes osteochondral regeneration through M2 macrophage polarization in a rabbit model.

Osteochondral regeneration is an orchestrated process of inflammatory immunity, host cell response, and implant degradation in tissue engineering. Here, the effects of a platelet-rich plasma (PRP)-gelatin methacryloyl (GelMA) hydrogel scaffold fabricated using the digital micro-mirror device (DMD) technique for osteochondral repair were investigated in a rabbit model. GelMA hydrogels with different PRP concentrations were fabricated, and their roles in bone marrow mesenchymal stem cells (BMSCs) and macrophage polarization in vitro were investigated. The incorporation of 20% PRP into the hydrogel showed optimal effects on the proliferation, migration, and osteogenic and chondrogenic differentiation of BMSCs. The 20% PRP-GelMA (v/v) hydrogel also promoted M2 polarization with high expression of Arg1 and CD206. Compared to the 20% PRP group, the 50% PRP group showed similar biological roles in BMSCs but less extent of osteogenesis. In the vivo study, the 20% PRP-GelMA composite was used for osteochondral reconstruction and showed more cartilage and subchondral bone regeneration than that observed using the pure GelMA hydrogel. The PRP-GelMA group exhibited more M2 macrophage infiltration and less M1 macrophage presentation at three time points as compared to the nontreatment group. The expression of Arg1 in the PRP-GelMA group increased significantly at 6 weeks but decreased to a lower level at 12 weeks, while CD163 showed sustained high expression until 18 weeks. Our findings demonstrated that the 3D-printed PRP-GelMA composite could promote osteochondral repair through immune regulation by M2 polarization and could be a potential candidate for osteochondral tissue engineering. STATEMENT OF SIGNIFICANCE: PRP-GelMA hydrogels promoted the migration and osteogenic and chondrogenic differentiation of BMSCs. PRP-GelMA hydrogels participated in immune regulation and M1-to-M2 transition of macrophages. PRP-GelMA hydrogels coordinated and promoted several overlapping osteochondral repair events, including dynamic immune regulation, chemotaxis of MSCs, and osteochondral differentiation. PRP-GelMA hydrogels showed superior cartilage and subchondral bone repair properties.

Autologous Micro-Fragmented Adipose Tissue as Stem Cell-Based Natural Scaffold for Cartilage Defect Repair.

Osteoarthritis (OA) poses a tough challenge worldwide. Adipose-derived stem cells (ASCs) have been proved to play a promising role in cartilage repair. However, enzymatic digestion, ex vivo culture and expansion, with significant senescence and decline in multipotency, limit their application. The present study was designed to obtain micro-fragmented adipose tissue (MFAT) through gentle mechanical force and determine the effect of this stem cell-based natural scaffold on repair of full-thickness cartilage defects. In this study, ASCs sprouted from MFAT were characterized by multi-differentiation induction and flow cytometry. Scratch and transwell migration assays were operated to determine whether MFAT could promote migration of chondrocytes in vitro. In a rat model, cartilage defects were created on the femoral groove and treated with intra-articular injection of MFAT or PBS for 6 weeks and 12 weeks (n = 12). At the time points, the degree of cartilage repair was evaluated by histological staining, immunohistochemistry and scoring, respectively. Two unoperated age-matched animals served as native controls. ASCs derived from MFAT possessed properties to differentiate into adipocytes, osteocytes and chondrocytes, with expression of mesenchymal stem cell markers (CD29, 44, 90) and no expression of hematopoietic markers (CD31, 34, 45). In addition, MFAT could significantly promote migration of chondrocytes. MFAT-treated defects showed improved macroscopic appearance and histological evaluation compared with PBS-treated defects at both time points. After 12 weeks of treatment, MFAT-treated defects displayed regular surface, high amount of hyaline cartilage, intact subchondral bone reconstruction and corresponding formation of type I, II, and VI collagen, which resembled the normal cartilage. This study demonstrates the efficacy of MFAT on cartilage repair in an animal model for the first time, and the utility of MFAT as a ready-to-use therapeutic alternative to traditional stem cell therapy.

In vitro Chondrocyte Responses in Mg-doped Wollastonite/Hydrogel Composite Scaffolds for Osteochondral Interface Regeneration.

The zone of calcified cartilage (ZCC) is the mineralized region between the hyaline cartilage and subchondral bone and is critical in cartilage repair. A new non-stoichiometric calcium silicate (10% Ca substituted by Mg; CSi-Mg10) has been demonstrated to be highly bioactive in an osteogenic environment in vivo. This study is aimed to systematically evaluate the potential to regenerate osteochondral interface with different amount of Ca-Mg silicate in hydrogel-based scaffolds, and to compare with the scaffolds containing conventional Ca-phosphate biomaterials. Hydrogel-based porous scaffolds combined with 0-6% CSi-Mg10, 6% ß-tricalcium phosphate (ß-TCP) or 6% nanohydroxyapatite (nHAp) were made with three-dimensional (3D) printing. An increase in CSi-Mg10 content is desirable for promoting the hypertrophy and mineralization of chondrocytes, as well as cell proliferation and matrix deposition. Osteogenic and chondrogenic induction were both up-regulated in a dose-dependent manner. In comparison with the scaffolds containing 6% ß-TCP or nHAp, human deep zone chondrocytes (hDZCs) seeded on CSi-Mg10 scaffold of equivalent concentration exhibited higher mineralization. It is noteworthy that the hDZCs in the 6% CSi-Mg10 scaffolds maintained a higher expression of the calcified cartilage zone specific extracellular matrix marker and hypertrophic marker, collagen type X. Immunohistochemical and Alizarin Red staining reconfirmed these findings. The study demonstrated that hydrogel-based hybrid scaffolds containing 6% CSi-Mg10 are particularly desirable for inducing the formation of calcified cartilage.

Atomically dispersed Au catalysts supported on CeO2 foam: controllable synthesis and CO oxidation reaction mechanism.

CO oxidation is a typical heterogeneous catalytic reaction. Development of active and stable low-temperature CO oxidation catalysts has been one of the hot topics in the field of catalysis. In this work, we explored the catalytic application of a series of Au catalysts supported on CeO2 foam using a modified deposition-precipitation method for CO oxidation. Among them, the catalyst with 1.1% Au loading content showed the highest catalytic activity, leading to the CO total conversion at 20 °C. Based on the strategy of stepwise reduction of Au loading content, we finally obtained the atomically monodisperse Au/CeO2 catalyst with high stability and strong resistance to elevated temperature, on which in situ DRIFTS analysis and DFT study were further performed to study the possible reactive site. Our results implied that the Au atoms on the CeO2 foam are the more stable sites for CO adsorption on the catalysts.