Sensory Nerves Directly Promote Osteoclastogenesis By Secreting CYP40

【Background】Sensory nerves play an important role in the regulation of bone homeostasis.In the process of fracture repair,sensory nerve ingrowth precedes vascular ingrowth,bone formation and many other processes,which are the earliest events.After the mouse sensory nerve is injured,both the blood vessel formation and new bone formation ability decrease.During the development of long bones,sensory nerve growth is very important for the ossification of primary and secondary ossification centers.In contemporary society,bone defects caused by traffic injuries,bone tumors,osteomyelitis,and bone infections have brought tremendous pressure to the national economy and psychology;regenerative medicine and tissue engineering technology do not need to cause secondary injury to patients because of their convenient sources.It has become an ideal method for bone defect repair.However,due to the large defect area of ??large segment of bone defect,the nutrition in the center area of ??the tissue engineering bone to repair it cannot be reached,so that the tissue engineering bone cannot be successfully constructed.Based on the above,the research group constructed a neuralized tissue engineered bone in the early stage and found that the implantation of sensory nerves can effectively promote the repair of large-scale bone defects;mechanism studies have found that the sensory nerves can adjust the seed cells built in the tissue engineered bone marrow mesenchyme Bone marrow stem cell(BMSC)promotes the formation of new bone.However,the effect of sensory nerves on material degradation and osteoclasts has not been studied.【Objectives】1.Explore the effect of sensory nerves on material degradation2.Explore the effect of sensory nerves on osteoclasts3.Explore the mechanism of sensory nerves regulating osteoclasts【Method】By using innervated tissue engineered bone and femur drilling bone defect models,as well as in in vitro experiments,the roles of sensory nerves on material degradation and osteoclasts were studied;By using i TRAQ screening,immunofluorescence verification,lentiviral infection to regulate target gene expression,and related functional experiments,the key factors of sensory nerves regulating osteoclasts were explore;By using immunoelectron microscopy,immunofluorescence staining,exosome extraction,Western blot,the transportation of key factors between sensory nerves and osteoclasts were traced;By using immunofluorescence staining colocalization,immunoprecipitation,Western blot,RT-PCR and other techniques,the molecular mechanism of sensory nerves regulating osteoclasts were explore.【Results】Here,we found that abundant sensory nerve signals are transported into bone cells,including osteoclasts.Sensory nerves directly promoted osteoclastogenesis in innervated tissue engineered bone and femur drilling bone defect models,as well as in in vitro experiments.Furthermore,a novel neuropeptide,CYP40,was found by screening the secreted proteins in sensory nerves.CYP40 is crucial in the direct promotion.It was found to bind the aryl hydrocarbon receptor(AHR)and downregulate AHR and RAS/C-RAF/P-ERK.In turn,this alleviated the inhibition of NFATc1 by P-ERK,to promote osteoclastogenesis.These findings revealed a novel mechanism of sensory nerves on bone regulation: the direct promotion of osteoclastogenesis by the sensory nerves.This mechanism may represent a direct,and quick response of sensory nerves to the changes in bone.【Conclusion】The sensory nerves secrete CYP40 bind to the aryl hydrocarbon receptor(AHR)and downregulate AHR and RAS/C-RAF/P-ERK.In turn,this alleviated the inhibition of NFATc1 by P-ERK,to promote osteoclastogenesis.This mechanism may represent a direct,and quick response of sensory nerves to the changes in bone.