Cell-free therapy based on extracellular vesicles: a promising therapeutic strategy for peripheral nerve injury.

Peripheral nerve injury (PNI) is one of the public health concerns that can result in a loss of sensory or motor function in the areas in which injured and non-injured nerves come together. Up until now, there has been no optimized therapy for complete nerve regeneration after PNI. Exosome-based therapies are an emerging and effective therapeutic strategy for promoting nerve regeneration and functional recovery. Exosomes, as natural extracellular vesicles, contain bioactive molecules for intracellular communications and nervous tissue function, which could overcome the challenges of cell-based therapies. Furthermore, the bioactivity and ability of exosomes to deliver various types of agents, such as proteins and microRNA, have made exosomes a potential approach for neurotherapeutics. However, the type of cell origin, dosage, and targeted delivery of exosomes still pose challenges for the clinical translation of exosome therapeutics. In this review, we have focused on Schwann cell and mesenchymal stem cell (MSC)-derived exosomes in nerve tissue regeneration. Also, we expressed the current understanding of MSC-derived exosomes related to nerve regeneration and provided insights for developing a cell-free MSC therapeutic strategy for nerve injury.

Tissue-Engineered Core-Shell Silk-Fibroin/Poly-l-Lactic Acid Nerve Guidance Conduit Containing Encapsulated Exosomes of Human Endometrial Stem Cells Promotes Peripheral Nerve Regeneration.

Nerve guide conduits (NGCs) have been shown to be less efficient than nerve autografts in peripheral nerve regeneration. To address this issue, we developed for the first time a novel tissue-engineered nerve guide conduit structure encapsulated with human endometrial stem cell (EnSC) derived exosomes, which promoted nerve regeneration in rat sciatic nerve defects. In this study, we initially indicated the long-term efficacy and safety impacts of newly designed double layered SF/PLLA nerve guide conduits. Then the regeneration effects of SF/PLLA nerve guide conduits containing exosomes derived from human EnSCs were evaluated in rat sciatic nerve defects. The human EnSC derived exosomes were isolated from the supernatant of human EnSC cultures and characterized. Subsequently, the human EnSC derived exosomes were encapsulated in constructed NGCs by fibrin gel. For in vivo studies, entire 10 mm peripheral nerve defects were generated in rat sciatic nerves and restored with NGC encapsulated with human EnSC derived exosomes (Exo-NGC group), nerve guide conduits, and autografts. The efficiency of the NGCs encapsulated with human EnSCs derived exosomes in assisting peripheral nerve regeneration was investigated and compared with other groups. The in vivo results demonstrated that encapsulated human EnSC derived exosomes in NGC (Exo-NGC) significantly benefitted nerve regeneration based on motor function, sensory reaction, and electrophysiological results. Furthermore, immunohistochemistry with histopathology results showed the formation of regenerated nerve fibers, along with blood vessels that newly were developed, as a result of the exosome functions in the Exo-NGC group. These outcomes illustrated that the newly designed core-shell SF/PLLA nerve guide conduit encapsulated with human EnSC derived exosomes enhanced the regeneration process of axons and improved the functional recovery of rat sciatic nerve defects. So, encapsulated human EnSC-derived exosomes in a core-shell SF/PLLA nerve guide conduit are a potential therapeutic cell-free treatment for peripheral nerve defects.

Portable hand-held bioprinters promote in situ tissue regeneration.

Three-dimensional bioprinting, as a novel technique of fabricating engineered tissues, is positively correlated with the ultimate goal of regenerative medicine, which is the restoration, reconstruction, and repair of lost and/or damaged tissue function. The progressive trend of this technology resulted in developing the portable hand-held bioprinters, which could be used quite easily by surgeons and physicians. With the advent of portable hand-held bioprinters, the obstacles and challenges of utilizing statistical bioprinters could be resolved. This review attempts to discuss the advantages and challenges of portable hand-held bioprinters via in situ tissue regeneration. All the tissues that have been investigated by this approach were reviewed, including skin, cartilage, bone, dental, and skeletal muscle regeneration, while the tissues that could be regenerated via this approach are targeted in the authors' perspective. The design and applications of hand-held bioprinters were discussed widely, and the marketed printers were introduced. It has been prospected that these facilities could ameliorate translating the regenerative medicine science from the bench to the bedside actively.

A comparison study on the behavior of human endometrial stem cell-derived osteoblast cells on PLGA/HA nanocomposite scaffolds fabricated by electrospinning and freeze-drying methods.

BACKGROUND: An engineered tissue structure is an artificial scaffold combined with cells and signaling factors. Among various polymers, the polylactide-co-glycolide/hydroxyapatite (PLGA/HA) has attracted much attention due to their optimal properties. The aim of this study was to study the behavior of human endometrial stem cell (hEnSC)-derived osteoblast cells cultured on PLGA/HA nanocomposite scaffolds. METHODS: hEnSCs were isolated and exposed to osteogenic media for 21 days. Differentiated cells were cultured on PLGA/HA synthetic scaffolds. The PLGA/HA-based nanocomposite scaffolds were fabricated using either electrospinning or freeze-drying methods. Behavior of the cells was evaluated a week after seeding hEnSC-derived osteoblast-like cells on these scaffolds. Osteogenesis was investigated in terms of alkaline phosphatase activity, gene expression, immunocytochemistry (ICC), proliferation, and scanning electron microscopy (SEM). Moreover, scaffold properties, such as pore size and morphology of the cells, onto the scaffolds were evaluated using SEM. Furthermore, biocompatibility of these scaffolds was confirmed by 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. RESULTS: The matrix mineralization was proved by alizarin red staining, and the osteogenic media-treated cultures positively expressed osteocalcin and osteopontin markers. Moreover, qRT-PCR results confirmed the positive gene expression of osteopontin and osteonectin in the differentiated osteoblast-like cells. The results of behavior assessment of the cultured cells on electrospinning and freeze-dried scaffolds showed that the behavior of the cultured cells on the freeze-dried PLGA/HA scaffolds was significantly better than the electrospinning PLGA/HA scaffolds. CONCLUSION: It has been shown that the freeze-dried PLGA/HA nanocomposite scaffolds can appropriately support the attachment and proliferation of the differentiated osteoblast cells and are a suitable candidate for bone tissue engineering.