The Role And Mechanism Of MIF In P.acnes-induced Intervertebral Disc Degeneration

ObjectiveTo investigate the role and molecular mechanism of MIF in P.acnes-induced disc degeneration.MethodsThe disc tissues of patients undergoing lumbar discectomy from March 2018 to March 2019 were collected and divided into normal group(N=5)and degenerative group(N=10)according to Pfirrmann classification.Immunohistochemistry was used to determine the expression levels of MMP-13,Col-II,and MIF in the endplate regions of the two groups.Ten male Sprague Dawley rats were divided into two groups using a random number table method,and 5ul P.acnes or PBS was injected into the endplate of the rat disc(L3/4,L4/5)to establish an animal model.The the endplate region was obtained for immunohistochemistry to detect the expression levels of MMP-13,Col-II and MIF.The rat intervertebral disc endplate cells were extracted and cultured in vitro,and different concentrations of P.acnes supernatant,recombinant MIF,MIF inhibitor or NF-κB pathway inhibitor were used to stimulate the endplate cells.The expression levels of MIF,MMP-13,Col-II,IL-6 and IL-1β were detected by Western Blot and RT-PCR.ResultCompared with human normal discs,the immunohistochemical results of patients with degenerative discs showed high expression of MIF and MMP-13,and the decreased expression of Col-II(p<0.01).P.acnes-induced degeneration of intervertebral discs showed high expression of MIF and MMP-13,and decreased expression of Col-II(p<0.01).The culture of rat endplate cells in vitro further revealed the molecular mechanism of P.acnes-induced disc degeneration.First,compared with the control group,P.acnes supernatant can increase the expression of MIF and MMP-13 and decrease the expression of Col-II in endplate cells(p<0.01);secondly,compared with the control group,recombinant MIF can increase the expression of MMP-13 and decrease the expression of Col-II(p<0.01),and at the same time promote the expression of inflammatory factors IL-6 and IL-1β(p<0.01);in addition,at the protein level and gene level,MIF inhibitors(4-IPP)can reduce the expression of MMP-13 and increase the expression of Col-II in endplate cells(p<0.01),thereby reversing P.acnes-induced degeneration of cartilage endplates;finally,high concentration of NF-κB signaling pathway inhibitor BAY-7082 can inhibit P.acnes-induced MIF expression levels(p<0.01),while ERK1/2 inhibitor FR-180204 had little effect for the expression of MIF(p>0.05).In summary,this molecular mechanism proves that P.acnes may promote MIF expression through the NF-κB signaling pathway and induce disc degeneration.ConclusionP.acnes can induce disc degeneration,and its mechanism may be related to the regulation of NF-κB signaling pathway to promote MIF expression.