Expression And Significance Of Insulin-like Growth Factor Binding Protein 6 (IGFBP6) In CIA Rats

Objective: Rheumatoid arthritis(RA)is a chronic,systemic autoimmune disease characterized by aggressive,symmetric polyarthritis.It can also be accompanied by complicated extra-articular manifestations,and current studies have also found that RA can increase the incidence of many diseases.The pathogenesis of RA is still unclear.At present,it is mainly believed that it is affected by many factors such as immunity,genetics and environment.In recent years,six high-affinity insulin-like growth factor binding protein(IGFBPs)families have been found to be major regulators of IGF action.It has been proven to be one of the regulatory factors in many biological processes such as cell cycle,proliferation,and metabolism.Abnormal expression of IGFBPs involves pathological processes of many diseases,such as tumors,cardiovascular diseases,digestive diseases,endocrine diseases,and the like.Insulin-like growth factor binding protein-6(IGFBP6)belongs to IGFBPs and has a role of inhibiting cell proliferation and angiogenesis,and inducing apoptosis and cell migration in tumors,depending on or independent of IGF.It can function in the intracellular and nucleus,respectively,and its differential expression is found in a variety of diseases.Because IGFBP6 is highly homologous between rat and human.It has also been demonstrated that a collagen-induced arthritis(CIA)rat model is a useful model for identifying RA susceptibility and related chronic inflammatory autoimmune diseases.The use of the CIA rat model can reduce the differences between the subjects and make people more aware of the complex pathological mechanisms of RA.Therefore,the CIA rat model was selected to study the differential expression and correlation of IGFBP6 in RA.At present,although methotrexate(MTX)is widely used in the treatment of RA,MTX treatment is severely affected by side effects,which limits its application.Therefore,this study also considered the changes of IGFBP6 under the action of MTX,looking for potential biomarkers of MTX on RA,and finding new targets for the treatment of RA.Methods:Twenty-four Wistar rats were divided into normal group,CIA group and CIA + MTX group.The normal group was compared,the CIA group wasmodeled with type II collagen secondary immunization,and the CIA + MTX group was treated with methotrexate(1.5 mg/kg)on the basis of modeling.The expression of IGFBP6 in serum,synovium and spleen of three groups of rats was detected by enzyme-linked immunosorbent assay and Western blot and reverse transcriptase polymerase chain reaction at the protein and mRNA levels,and the expression of IGFBP6 and arthritis index were analyzed.The correlation between them.Results:1.The level of IGFBP6 in serum was significantly higher in the serum of rats in the CIA group compared with the normal group.After administration,serum IGFBP6 levels were significantly reduced,but there were still some differences compared to the normal group.In the CIA group,the serum concentration of IGFBP6 was positively correlated with the arthritic index score of CIA rats,but not in the normal group and the CIA+MTX group.2.The level of IGFBP6 in the synovial and spleen samples was significantly increased in the synovial and spleen samples from the CIA group compared with the control group.In contrast,MTX administration reduced the increase in IGFBP6 in the synovial and spleen of the CIA rat model,but there were some significant differences compared to the control group.3.IGFBP6 mRNA levels in synovial and spleen samples.IGFBP6 mRNA levels in synovial samples in the CIA group were significantly higher than in the normal group and significantly decreased after MTX administration.The spleen has a similar change.Furthermore,IGFBP6 mRNA levels in the synovium and spleen were positively correlated with the arthritis index in the CIA group,but this was not observed in the normal group and the CIA+MTX group.Conclusion: In conclusion,our data highlight the high expression of IGFBP6 in CIA rats compared to the control group,and demonstrate that it is positively correlated with disease activity.Hence,IGFBP6 should be further investigated as a possible marker of the severity of RA.At the same time,IGFBP6 expression can be down-regulated by the action of MTX,indicating that IGFBP6 may be a new potential therapeutic target for the action of MTX in the treatment of RA.