miRNA-21-5p is an important contributor to the promotion of injured peripheral nerve regeneration using hypoxia-pretreated bone marrow-derived neural crest cells

Our previous study found that rat bone marrow–derived neural crest cells(acting as Schwann cell progenitors)have the potential to promote long-distance nerve repair.Cell-based therapy can enhance peripheral nerve repair and regeneration through paracrine bioactive factors and intercellular communication.Nevertheless,the complex contributions of various types of soluble cytokines and extracellular vesicle cargos to the secretome remain unclear.To investigate the role of the secretome and extracellular vesicles in repairing damaged peripheral nerves,we collected conditioned culture medium from hypoxia-pretreated neural crest cells,and found that it significantly promoted the repair of sensory neurons damaged by oxygen-glucose deprivation.The mRNA expression of trophic factors was highly expressed in hypoxia-pretreated neural crest cells.We performed RNA sequencing and bioinformatics analysis and found that miR-21-5p was enriched in hypoxia-pretreated extracellular vesicles of neural crest cells.Subsequently,to further clarify the role of hypoxia-pretreated neural crest cell extracellular vesicles rich in miR-21-5p in axonal growth and regeneration of sensory neurons,we used a microfluidic axonal dissociation model of sensory neurons in vitro,and found that hypoxia-pretreated neural crest cell extracellular vesicles promoted axonal growth and regeneration of sensory neurons,which was greatly dependent on loaded miR-21-5p.Finally,we constructed a miR-21-5p-loaded neural conduit to repair the sciatic nerve defect in rats and found that the motor and sensory functions of injured rat hind limb,as well as muscle tissue morphology of the hind limbs,were obviously restored.These findings suggest that hypoxia-pretreated neural crest extracellular vesicles are natural nanoparticles rich in miRNA-21-5p.miRNA-21-5p is one of the main contributors to promoting nerve regeneration by the neural crest cell secretome.This helps to explain the mechanism of action of the secretome and extracellular vesicles of neural crest cells in repairing damaged peripheral nerves,and also promotes the application of miR-21-5p in tissue engineering regeneration medicine.

Double-edge Role of B Cells in Tumor Immunity:Potential Molecular Mechanism

B cells are a heterogeneous population,which have distinct functions of antigen presentation,activating T cells,and secreting antibodies,cytokines as well as protease.It is supposed that the balance among these B cells subpopulation(resting B cells,activated B cells,Bregs,and other differentiated B cells)will determine the ultimate role of B cells in tumor immunity.There has been increasing evidence supporting opposite roles of B cells in tumor immunity,though there are no general acceptable phenotypes for them.Recent years,a new designated subset of B cells identified as Bregs has emerged from immunosuppressive and/or regulatory functions in tumor immune responses.Therefore,transferring activated B cells would be possible to become a promising strategy against tumor via conquering the immunosuppressive status of B cells in future.Understanding the potential mechanism of double-edge role of B cells will help researchers utilize activated B cells to improve their anti-tumor response.Moreover,the molecular pathways related to B cell differentiation are involved in its tumor-promoting effect,such as NF-κB,STAT3,BTK.So,we review the molecular and signaling pathway mechanisms of B cells involved in both tumor-promoting and tumor-suppressive immunity,in order to help researchers optimize B cells to fight cancer better.