Background Mesenchymal stem cells (MSCs) exosomes were previously shown to be effective in articular cartilage repairing. However, whether MSCs exosomes promote mature cartilage formation of microtia chondrocytes and the underlying mechanism of action remains unknown. Additionally, some hurdles, such as the low yield and unsatisfactory therapeutic effects of natural exosomes have emerged when considering the translation of exosomes-therapeutics to clinical practices or industrial production. Herein, we investigated the roles of human adipose-derived stem cells (ADSCs) exosomes in modulating microtia chondrocytes and the underlying mechanism of action. Special attention was also paid to the mass production and functional modification of ADSCs exosomes. Results We firstly used porous gelatin methacryloyl (Porous Gelma) hydrogel with pores size of 100 to 200 μm for 3D culture of passage 2, 4 and 6 ADSCs (P2, P4 and P6 ADSCs, respectively), and obtained their corresponding exosomes (Exo 2, Exo 4 and Exo 6, respectively). In vitro results showed Exo 2 outperformed both Exo 4 and Exo 6 in enhancing cell proliferation and attenuating apoptosis. However, both Exo 4 and Exo 6 promoted chondrogenesis more than Exo 2 did. Small RNA sequencing results indicated Exo 4 was similar to Exo 6 in small RNA profiles and consistently upregulated PI3K/AKT/mTOR signaling pathway. Notably, we found hsa-miR-23a-3p was highly expressed in Exo 4 and Exo 6 compared to Exo 2, and they modulated microtia chondrocytes by transferring hsa-miR-23a-3p to suppress PTEN expression, and consequently to activate PI3K/AKT/mTOR signaling pathway. Then, we designed genetically engineered exosomes by directly transfecting agomir-23a-3p into parent P4 ADSCs and isolated hsa-miR-23a-3p-rich exosomes for optimizing favorable effects on cell viability and new cartilage formation. Subsequently, we applied the engineered exosomes to in vitro and in vivo tissue-engineered cartilage culture and consistently found that the engineered exosomes could enhance cell proliferation, attenuate apoptosis and promote cartilage regeneration. Conclusions Taken together, the porous Gelma hydrogel could be applied to exosomes mass production, and functional modification could be achieved by selecting P4 ADSCs as parent cells and genetically modifying ADSCs. Our engineered exosomes are a promising candidate for tissue-engineered ear cartilage regeneration. Graphical Abstract

Objectives To investigate current situation of minimal information implementation highlighted by minimal information for studies of extracellular vesicles 2018 (MISEV2018) guidelines, and explore technological advances towards mass production and functional modification in aesthetic, plastic and reconstructive surgery. Methods Original articles on extracellular vesicles (EVs) of adipose stem cells (ASCs) were identified. Statistics upon minimal information for EVs research, such as species, cell types, culture conditions, conditioned media harvesting parameters, EVs isolation/storage/identification/quantification, functional uptake and working concentration, were analyzed. Results The items of cell culture conditions such as passage number, seeding density, conditioned media harvesting time, functional uptake and working concentration were poorly documented, with a reporting percentage of 47.13%, 54.02%, 29.89%, 62.07% and 36.21%, respectively. However, there were some studies not reporting information of ASCs origin, culture medium, serum, EVs isolation methods, quantification and identification of EVs, accounting for 3.45%, 10.34%, 6.90%, 3.45%, 18.39% and 4.02%, respectively. Serum deprivation and trophic factors stimuli were attempted for EVs mass production. Several technological advances towards functional modification included hypoxia pre-condition, engineering EVs and controlled release. Presently, ASCs EVs have been applied in multiple fields, including diabetic/non-diabetic wound healing, angiogenesis, inflammation modulation, fat grafting, hair regeneration, antiaging, and healing and regeneration of cartilage/bone/peripheral nerve/tendon. Conclusion Our results highlight normative reporting of ASCs EVs in functional studies to increase reliability and reproducibility of scientific publications. The advances towards mass production and functional modification of ASCs EVs are also recommended to enhance therapeutic effects.

Background: Uncontrollable inflammatory response following ectopic engineered cartilage implantation is devastating to the aesthetic and functional outcomes of the recipients. Adipose stem cells (ASCs) have a good immunomodulatory capacity via a paracrine mechanism. However, works of literature are scarce regarding ASC modulation in ectopic engineered cartilage regeneration in vivo. This study aims to explore how ASCs modulate the inflammatory response after engineered cartilage implantation and affect the implants in a nonchondrogenic milieu in large immunocompetent animals. Methods: Porcine engineered elastic cartilages were cultured in vitro for 3 weeks with chondrocyte cell sheeting technology and then assigned into two groups: ASCs and Control (saline injection). All samples (n= 6 per group) were autologously implanted into different subcutaneous pockets, and a single dose of ASCs was injected at three points around the implant. All samples were harvested after 2 weeks in vivo for analysis. Results: In the examination of inflammation, we observed reduced inflammatory cell infiltration and improved M2 macrophage polarization in the implanted engineered cartilage with ASC injection compared to the control. There were also enhanced anti-inflammatory cytokines and reduced proinflammatory cytokines inside and adjacent to the implants, while in serum, there were no significant differences. In the examination of the cartilage quality, there were significant increases of cartilage extracellular matrix and chondrogenic factors, and the elastic cartilage phenotype was maintained compared to control. Conclusion: This study finds that a single dose of ASCs can promote ectopic cartilage regeneration by modulating inflammation and enhancing cartilage matrix synthesis in a porcine model.