Effects Of Bisphosphonates On Macrophage Polarization In Animal Models Of Associated Jaw Necrosis

Objective: By studying the changes of macrophage polarity in animal models of bisphosphonate-related jaw necrosis,the mechanism of bisphosphonate-related jaw necrosis was explored.The effects of IL-17 on bisphosphonate-related jaw necrosis in animal models were also explore.Methods: Rats were given intravenous zoledronic acid(0.2 mg / kg,once / week)for 3 consecutive weeks.At 4 weeks,bilateral first mandibular molars were extracted.The rats were given intravenous zoledronic acid(0.2 mg / kg,once a week)for 4 consecutive weeks to complete the establishment of a bisphosphonate-related rat model.Rats were treated with IL-17 neutralizing antibodies and laquinimod during animal model establishment.Rats were divided into control group(injected with normal saline),ZA group(injected zoledronic acid),IL-17 group(injected zoledronic acid + IL-17 neutralizing antibody),and Laq group(injected zoledronic acid + Gavage laquinimod).X-ray films and Micro-CT were used to examine the healing of tooth extraction wounds in rats.Then,the bone tissue of rat tooth extraction site was taken,and the expression of markers of macrophages(CD68 +),M1-type cells(iNOS +)and M2-type cells(CD206 +)was detected by immunofluorescence.Results: 1.In the clinical observation,it was found that the healing of the tooth extraction wound in the control group was good,and no dead bone was formed.The rats in the experimental group showed symptoms such as delayed healing of the extraction wound,and empty tooth sockets.The incidence of BRONJ in rats in the ZA group was 80%,and the incidence of rats in the IL-17 group and the Laq group decreased.2.X-ray and Micro-CT examinations showed that BRONJ rats exhibited reduced bone density,decreased bone volume fraction,poor osteogenesis,and varying degrees of dead bone formation.There was no difference in bone mineral density in the extraction site of the control group compared with surrounding bone tissue.3.The immunofluorescence test results showed that compared with the control group rats,a large amount of CD68 + macrophage infiltration was observed in the ZA group rats.At the same time,iNOS-positive macrophages also showed high expression,while CD206-positive macrophages were significantly reduced.There is a tendency that the polarization of M1 cells increases and the polarization of M2 cells decreases.4.The expression levels of CD68 + cells,iNOS + cells,and CD206 + cells in the ZA group,IL-17 group and Laq group were significantly different from those in the control group.However,compared with ZA group,the expression of iNOS + cells in ZA + IL-17 neutralizing antibody and ZA + Laq decreased,while the expression of CD206 + cells increased.This indicates that the IL-17 and Laq groups inhibited the tendency of macrophages to polarize to M1 type.5.Compared with non-BRONJ rats,the ratio of M1 type cells to M2 type cells is more obvious in BRONJ rats.This shows that M1 macrophages have a promoting role in the formation of BRONJ in rats,and it is an important part of the pathogenesis of BRONJ in rats.Conclusion: An animal model of bisphosphonate-related jaw necrosis was successfully established by intravenous injection of zoledronic acid.BRONJ rats may experience delayed healing of tooth extraction wounds,empty tooth sockets,decreased bone density,and varying degrees of dead bone formation.Zoledronic acid(ZA)can cause a large number of macrophages to aggregate and polarize to M1-type cells.Tissue destruction caused by excessive M1 cell polarization may be an important part of the pathogenesis of BRONJ.Blocking or inhibiting IL-17 activity can help reduce the incidence of BRONJ rats,and can significantly reduce the infiltration of M1 macrophages around tooth extraction wounds in rats.IL-17-mediated polarization of M1 macrophages may be involved in the occurrence of BRONJ.Drugs that block or inhibit IL-17 activity may play a role in preventing the occurrence of BRONJ in cancer patients taking bisphosphonates.