Biological Function and Mechanism of Bone Marrow Mesenchymal Stem Cells-packed Poly (3,4-ethylenedioxythiophene) (PEDOT) Scaffolds for Peripheral Nerve Injury: The Involvement of miR-21-Notch Signaling Pathway.

Ununited peripheral nerves represent attractive site for connectivity with neuroprostheses because their predictable internal topography allows precise sorting of motor and sensory signals. Also transplantation of bone marrow mesenchymal stem cells (BMSCs) is increasingly recognized as an effective method of restore the peripheral nervous system injury due to its neuron-directed differentiation potential. This study was to evaluate the in vivo performance of BMSCs-packed Poly(3,4-ethylenedioxythiophene) (PEDOT) scaffolds across a critical nerve conduction gap and examine the potential mechanism by which BMSCs-packed PEDOT scaffolds mediate peripheral nerve regeneration in rat model of recurrent laryngeal nerve (RLN) deletion. In this study, rat models of 8 mm-RLN deletion were randomly divided into three groups and respectively received transplantation of autologous nerve or PEDOT scaffolds or BMSCspacked PEDOT scaffolds. After transplantation, neurological function was assessed by laryngeal electromyography. BMSCs-directed neuron differentiation was induced and confirmed by the upregulation of 6 nerve cell markers. Expression level of miRs, Notch signals and 6 nerve cell markers in nerve grafts or cells were determined by quantitative real-time PCR or western blot analysis. The results showed that BMSCs-packed PEDOT scaffolds transplantation significantly improved neurological function compared with PEDOT scaffolds alone. Regenerative nerve of BMSCs-packed PEDOT scaffolds showed higher expression level of miR-21 and Notch signals (Hes-1 and Notch intracellular domain (NICD)) than PEDOT alone. We found that the expression levels of miR-21, Hes-1 and NICD are increased with timecourse of neuron-directed differentiation stimulating of BMSCs. Meanwhile, both miR-21 overexpression and Notch pathway activation promote the expression of 6 nerve cell markers in BMSCs-directed neuron, whereas the inactivation of Notch pathway abrogates miR-21-inudced upregulation of 6 nerve cell markers. Moreover, knock-down of miR-21 suppresses the pro-neural restoration action of BMSCs-packed PEDOT scaffolds. In summary, our data suggested that BMSCs-packed PEDOT effectively repairs recurrent laryngeal nerve injury and the potential mechanism is miR-21- mediated Notch signal activation.