Wound healing is known as one of the most complicated biological processes for injured skin caused by surgical, trauma, burns, or diabetic diseases, which causes a nonfunctioning mass of fibrotic tissue. Recent reports have suggested that exosomes (EXOs) secreted by this type of stem cells may contribute to their paracrine effect. In this study, the EXOs were isolated from the supernatant of cultured adipose-derived stem cells (ADSCs) via ultracentrifugation and filtration. The EXO loaded in the alginate-based hydrogel was used as a bioactive scaffold to preserve the EXO in the wound site in the animal model. The physical and biochemical properties of EXO loaded Alg hydrogel were characterized and results proved that fabricated structure was biodegradable and biocompatible. This bioactive wound dressing technique has significantly improved wound closure, collagen synthesis, and vessel formation in the wound area. Results offer a new viewpoint and a cell-free therapeutic strategy, for wound healing through the application of the composite structure of EXO encapsulated in alginate hydrogel. K E Y W O R D S adipose-derived stem cells, alginate based hydrogel, exosomes, wound dressing, wound healing

Mesenchymal stem cells (MSCs) are adult multipotent cells that due to their ability to homing to damaged tissues and differentiate into specialized cells, are remarkable cells in the field of regenerative medicine. It's suggested that the predominant mechanism of MSCs in tissue repair might be related to their paracrine activity. The utilization of MSCs for tissue repair is initially based on the differentiation ability of these cells; however now it has been revealed that only a small fraction of the transplanted MSCs actually fuse and survive in host tissues. Indeed, MSCs supply the microenvironment with the secretion of soluble trophic factors, survival signals and the release of extracellular vesicles (EVs) such as exosome. Also, the paracrine activity of EVs could mediate the cellular communication to induce cell-differentiation/self-renewal. Recent findings suggest that EVs released by MSCs may also be critical in the physiological function of these cells. This review provides an overview of MSC-derived extracellular vesicles as a hopeful opportunity to advance novel cell-free therapy strategies that might prevail over the obstacles and risks associated with the use of native or engineered stem cells. EVs are very stable; they can pass the biological barriers without rejection and can shuttle bioactive molecules from one cell to another, causing the exchange of genetic information and reprogramming of the recipient cells. Moreover, extracellular vesicles may provide therapeutic cargo for a wide range of diseases and cancer therapy.

Combat or burn injuries are associated with a series of risks, such as microbial infection, an elevated level of inflammatory response, and pathologic scar tissue formation, which significantly postpone wound healing and also lead to impaired repair. Skin engineering for wound healing requires a biomimetic dressing substrate with ideal hydrophilicity, holding antioxidant and antimicrobial properties. In addition, available bioactive specification is required to reduce scar formation, stimulate angiogenesis, and improve wound repair. In this study, we successfully fabricated chitosan (Ch)–based hydrogel enriched with isolated exosome (EXO) from easy‐accessible stem cells, which could promote fibroblast cell migration and proliferation in vitro. Full‐thickness excisional wound model was used to investigate the in vivo dermal substitution ability of the fabricated hydrogel composed Ch and EXO substrates. Our finding confirmed that the wounds covered with Ch scaffold containing isolated EXO have nearly 83.6% wound closure ability with a high degree of re‐epithelialization, whereas sterile gauze showed 51.5% of reduction in wound size. In summary, obtained results imply that Ch‐glycerol‐EXO hydrogel construct can be utilized at the full‐thickness skin wound substitution and skin tissue engineering.

Current hyaluronic acid‐based hydrogels often cause cytotoxicity to encapsulated cells and lack the adhesive property required for effective biomedical and tissue engineering applications. Provision of the cell‐adhesive surface is an important requirement to improve its biocompatibility. An aqueous solution of hyaluronic acid possessing phenolic hydroxyl (HA‐Ph) moieties is gellable via a horseradish peroxidase (HRP)‐catalyzed oxidative cross‐linking reaction. This study evaluates the effect of different degrees of cross‐linked Ph moieties on cellular adhesiveness and proliferation on the resultant enzymatically cross‐linked HA‐Ph hydrogels. Mechanical characterization demonstrated that the compression force of engineered hydrogels could be tuned in the range of 0.05–35 N by changing conjugated Ph moieties in the precursor formulation. The water contact angle and water content show hydrophobicity of hydrogels increased with increasing content of cross‐linked Ph groups. The seeded mouse embryo fibroblast‐like cell line and human cervical cancer cell line, on the HA‐Ph hydrogel, proved cell attachment and spreading with a high content of cross‐linked Ph groups. The HA‐Ph with a higher degree of Ph moieties shows the maximum degree of cell adhesion, spreading, and proliferation which presents this hydrogel as a suitable biomaterial for biomedical and tissue engineering applications.

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

Oral mesenchymal stem cells (MSCs) and their secretomes are considered important factors in the field of medical tissue engineering and cell free biotherapy due to their ease of access, differentiation potential, and successful therapeutic outcomes. Extracellular vesicles (EVs) and the conditioned medium (CM) from MSCs are gaining more attraction as an alternative to cell-based therapies due to the less ethical issues involved, and their easier acquisition, preservation, long term storage, sterilization, and packaging. Bone and periodontal regenerative ability of EVs and CM have been the focus of some recent studies. In this review, we looked through currently available literature regarding MSCs’ EVs or conditioned medium and their general characteristics, function, and regenerative potentials. We will also review the novel applications in regenerating bone and periodontal defects.

Background: Endometrium is recently introduced as an available source of mesenchymal stem cells (EnMSCs), which can be obtained without anesthesia and side effects. Regarding the issues and complexities of cell-based therapies, exosomes gain tremendous attention as a novel tool for cell-free therapies. Although several clinical trials are recently established based on therapeutic potential of EnMSCs, biological roles of EnMSC-derived exosomes are still unclear. Methods: The current study was conducted to investigate the potential effects of EnMSC-derived exosomes on proliferation, migration, and angiogenesis of human umbilical cord vein endothelial cells (HUVECs). For this purpose, EnMSCs and then EnMSC-derived exosomes were isolated and characterized. MTT assay and wound healing assay as well as tube formation assay were applied. Results: The collected data showed that EnMSC-derived exosomes significantly increased proliferation, migration, and angiogenesis of HUVECs. It was observed that the effects of exosomes were applied in a dose dependent manner. In addition, expression analysis by quantitative real-time PCR showed that increased expression of proliferation and angiogenesis genes in HUVECs were treated with EnMSC-derived exosomes in a dose dependent manner. Conclusions: The current study results showed that EnMSC-derived exosomes can exert biological effects such as their source cells and become new candidates for cell-free therapies. Taken together, increased angiogenesis makes EnMSC-derived exosomes a promising tool in regenerative medicine, especially wound healing and treatment of vascular disease.

Exosomes (EXOs) are naturally occurring nanosized lipid bilayers that can be efficiently used as a drug delivery system to carry small pharmaceutical, biological molecules and pass major biological barriers such as the blood-brain barrier. It was hypothesized that EXOs derived from human endometrial stem cells (hEnSCs-EXOs) can be utilized as a drug carrier to enhance tumor-targeting drugs, especially for those have low solubility and limited oral bioactivity. In this study, atorvastatin (Ato) loaded EXOs (AtoEXOs) was prepared and characterized for its physical and biological activities in tumor growth suppression of 3 D glioblastoma model. The AtoEXOs were obtained in different methods to maximize drug encapsulation efficacy. The characterization of AtoEXOs was performed for its size, stability, drug release, and in vitro anti-tumor efficacy evaluated comprising inhibition of proliferation, apoptosis induction of tumor cells. Expression of apoptotic genes by Real time PCR, Annexin V/PI, tunnel assay was studied after 72 h exposing U87 cells where encapsulated in matrigel in different concentrations of AtoEXOs (5, 10 μM). The results showed that the prepared AtoEXOs possessed diameter ranging from 30–150 nm, satisfying stability and sustainable Ato release rate. The AtoEXOs was up taken by U87 and generated significant apoptotic effects while this inhibited tumor growth of U87 cells. Altogether, produced AtoEXOs formulation due to its therapeutic efficacy has the potential to be an adaptable approach to treat glioblastoma brain tumors.