Adiponectin Inhibit The Migration Of Osteoclast Precursors From Bone Marrow To Peripheral Blood In CIA Mice

Backgrounds.Adiponectin is an adipocytokine secreted by the white adipose tissue(WAT).It plays an important role in the various physiological and pathological processes of inflammation,immunoregulation and metabolism.Previous studies have found that AD is highly expressed in the inflammatory joint of rheumatoid arthritis(RA).Journal of Arthritis and Rheumatism and other reports have suggested that AD is closely related to radiographic progression of bone erosion.But,The mechanism remains unclear.The traditional view that synovitis is the core mechanism of bone erosion.However,the latest research results found the disassociation of the link between synovitis and bone erosion.The current view support that RA bone erosion is strongly associated with bone marrow edema.Osteoclasts(OCs)is the most critical cell in bone erosion,fused and differentiated by the osteoclast precursors(Pre-OCs).Previous study related AD with OCs mainly concerned on AD indirectly influenced OCs by promoting the migration and invasion of rheumatoid arthritis synovial fibroblasts(RASFs)and the expression of inflammatory cytokines.However,whether AD directly regulates the migration and bone homeostasis of Pre-OCs remains unclear.Therefore,this study aimed to explore the influence of adiponectin on the migration and bone homeostasis of Pre-OCs.Study was divided into two parts.Part I The effects of adiponectin on the migration of osteoclast precursors Ojective.To investigate the direct effects of adiponectin(AD)on the migration of osteoclast precursors(Pre-OCs).Methods.The effect of adiponectin on the migration of osteoclast precursor cells was assessed by Transwell migration assay.RAW264.7 cells were put in the upper chamber,AD were added in the lower chamber.The numbers of RAW264.7 going through the upper chamber were counted after 24 hours.Relative expressions of chemokines in osteoclast precursors were assessed by RT-PCRResults.Transwell suggested The numbers going through the upper chamber were significantly decreased after adding AD 24 hours.Real-time PCR showed the relative expressions of CX3CR1 in osteoclast precursors were decreased,but the expressions of CXCR4 were no change.Conclusion.Adiponectin directly inhibits the osteoclast precursors migration via inhibiting the expression of CX3CR1 in the Pre-OCs.Part ? The effects of adiponectin on the bone homeostasis of osteoclast precursorsOjective.To investigate the effects of adiponectin on bone homeostasis of Pre-OCs and the mechanism.Methods.The RANKL mobilized Pre-OCs mice model and CIA model were established respectively.The RANKL mobilized Pre-OCs mice were intraperitoneal injection of AD,and CIA mice were articular cavity injection.Bone marrow cells and peripheral blood mononuclear cells Were collected and the numbers of Pre-OCs in them were detected by flow cytometry.The effect of adiponectin on osteoclastogenesis in CIA mice was assessed by TRAP staining,The effect of adiponectin on the SIP stimulated RAW264.7 migration was assessed by Transwell migration assay.Relative expressions of S1P1 and S1P2 in RAW264.7 and BMC of the CIA were assessed by RT-PCR.Results.Flow cytometric analysis showed that in the AD group of RANKL mobilized Pre-OCs mice,the proportion of Pre-OCs in bone marrow and PBMC was both decreased.In the AD group of CIA mice,the proportion of Pre-OCs was increased in bone marrow and decreased in PBMC.TRAP staining suggested AD increased the osteoclastogenesis in the bone marrow of CIA mice.Transwell suggested The numbers going through the upper chamber were significantly decreased in S1P stimulated RAW264.7 after adding AD 24 hours.The relative gene expression of S1P1 in RAW264.7 was decreased,but the expressions of S1P2 was no change.On the 35 days after the first immunization the relative expressions of S1P1 in the bone marrow cells of CIA mice was reduced.Conclusion.In RANKL mobilized Pre-OCs mice and CIA mice,adiponectin destruct bone homeostasis of osteoclast precursors via inhibiting the expression of S1P1,which is a novel mechanism distinct from previous report,suggesting adiponectin may be a unique therapeutic strategy for preventing bone erosion of RA.