Transcription factor networks involved in cell death in the dorsal root ganglia following peripheral nerve injury

The peripheral nervous system has the potential to regenerate after nerve injury owing to the intrinsic regrowth ability of neurons and the permissive microenvironment.The regenerative process involves numerous gene expression changes,in which transcription factors play a critical role.Previously,we profiled dysregulated genes in dorsal root ganglion neurons at different time points（0,3 and 9 hours,and 1,4 and 7 days） after sciatic nerve injury in rats by RNA sequencing.In the present study,we investigated differentially expressed transcription factors following nerve injury,and we identified enriched molecular and cellular functions of these transcription factors by Ingenuity Pathway Analysis.This analysis revealed the dynamic changes in the expression of transcription factors involved in cell death at different time points following sciatic nerve injury.In addition,we constructed regulatory networks of the differentially expressed transcription factors in cell death and identified some key transcription factors（such as STAT1,JUN,MYC and IRF7）.We confirmed the changes in expression of some key transcription factors（STAT1 and IRF7） by quantitative reverse transcription-polymerase chain reaction.Collectively,our analyses provide a global overview of transcription factor changes in dorsal root ganglia after sciatic nerve injury and offer insight into the regulatory transcription factor networks involved in cell death.

Prokaryotic expression of recombinant human p75NTR-Fc fusion protein and its effect on the neurite outgrowth of dorsal root ganglia neuron

Objective： To clone, express, and identify the extracellular domain gene of human p75 neurotrophin receptor with IgG-Fe （hp75NTR-Fc） in prokaryotic expression system, and investigate the effect of the recombinant protein on dorsal root ganglia （DRG） neuron neurites. Methods： The hp75NTR-Fc coding sequence was amplified from pcDNA-hp75NTR-Fc by polymerase chain reaction （PCR） and subcloned into vector pET30a （＋）, in which hp75NTR-Fc expression was controlled under the T7 promoter. The recombinant vectors were amplified in E. coli DH5α and identified by PCR, enzyme digestion and sequencing, and then transformed into E. coli BL21 （DE3）. The expression product was analyzed with SDS-PAGE and Western blot. Then after the recombinant protein purified with Protein A affinity chromatograph, and renaturated with dialysis, respectively, the effect of the recombinant protein on DRG neuron neuritis was further investigated. Results： The results of PCR, enzyme digestion, and sequencing demonstrated the success of inserting the hp75NTR-Fc fragment into vector pET30a （＋）. SDS-PAGE and Western blot showed a positive protein band with molecular weight about 50 kD in the expression product, which is accordant with the interest protein, and this band could be specifically recognized by rabbit anti-NGFRp75 antibody. The purified infusion protein following dialysis could promote neurite outgrowth of DRG neurons cultured with myelin-associated glycoprotein （MAG）. Conclusion： The hp75NTR-Fc coding sequence was subcloned into the expression vector pET30a （＋） correctly and expressed successfully in the prokaryotie expression system. The infusion protein could promote neurite outgrowth of DRG neurons cultured with MAG.

An update–tissue engineered nerve grafts for the repair of peripheral nerve injuries

Peripheral nerve injuries（PNI） are caused by a range of etiologies and result in a broad spectrum of disability. While nerve autografts are the current gold standard for the reconstruction of extensive nerve damage, the limited supply of autologous nerve and complications associated with harvesting nerve from a second surgical site has driven groups from multiple disciplines, including biomedical engineering, neurosurgery, plastic surgery, and orthopedic surgery, to develop a suitable or superior alternative to autografting. Over the last couple of decades, various types of scaffolds, such as acellular nerve grafts（ANGs）, nerve guidance conduits, and non-nervous tissues, have been filled with Schwann cells, stem cells, and/or neurotrophic factors to develop tissue engineered nerve grafts（TENGs）. Although these have shown promising effects on peripheral nerve regeneration in experimental models, the autograft has remained the gold standard for large nerve gaps. This review provides a discussion of recent advances in the development of TENGs and their efficacy in experimental models. Specifically, TENGs have been enhanced via incorporation of genetically engineered cells, methods to improve stem cell survival and differentiation, optimized delivery of neurotrophic factors via drug delivery systems（DDS）, co-administration of platelet-rich plasma（PRP）, and pretreatment with chondroitinase ABC（Ch-ABC）. Other notable advancements include conduits that have been bioengineered to mimic native nerve structure via cell-derived extracellular matrix（ECM） deposition, and the development of transplantable living nervous tissue constructs from rat and human dorsal root ganglia（DRG） neurons. Grafts composed of non-nervous tissues, such as vein, artery, and muscle, will be briefly discussed.