ABSTRACT
Objective:To explore the trans-membrane signaling mechanism of interleukin-6 (IL-6)-induced osteogenic differentiation and calcification of human umbilical artery smooth muscle cells (HUASMCs).Methods:HUASMCs were primarily cultured in vitro and were stimulated with IL-6, IL-6+solutable IL-6 receptor (sIL-6R), IL-6+sIL-6R+solutable gp130 (sgp130), or vehicle (blank control). Alizarin red and Von Kossa staining were used for detecting cell calcification, Western blot was used to test the protein expression of tissue-nonspecific alkaline phosphatase (TNAP), osteopontin (OPN), bone morphogenetic protein-2 (BMP-2) and Runt related transcription factor 2 (Runx2), and immunofluorescence was used to examine the mIL-6R expression of HUASMCs. The comparison of measurement date between the two groups was conducted by t-test. The comparison of measurement date between multiple groups was conducted by one-way analysis of variance (ANOVA). Results:The intensity severity of calcification stain was IL-6+sIL-6R group >IL-6+sIL-6R+sgp130 group>IL-6 group=blank control. After stimulated for 12 hours, the TNAP expression in blank control, IL-6 group, IL-6+sIL-6R group, IL-6+sIL-6R+sgp130 group were (0.44±0.08), (0.52±0.14), (0.84±0.16) and (0.55±0.10) respectively ( F=290.96, P<0.001). After stimulated for 3 days, the OPN expression in blank control, IL-6 group, IL-6+sIL-6R group, IL-6+sIL-6R+sgp130 group were (0.61±0.84), (0.95±0.16), (1.65±0.24) and (0.99±0.10) respectively ( F=507.72, P<0.001). After stimulated for 12 hours, the BMP-2 expression in blank control, IL-6 group, IL-6+sIL-6R group, IL-6+sIL-6R+sgp130 group were (0.77±0.05), (1.69±0.16), (2.81±0.26) and (0.57±0.12) respectively ( F=959.09, P<0.001). After stimulated for 3 days, the Runx2 expression in blank control, IL-6 group, IL-6+sIL-6R group,IL-6+sIL-6R+sgp130 group were (0.57±0.03) , (0.92±0.10), (1.31±0.13) and (0.66±0.06) respectively ( F=1141.27, P<0.001). Comparing with Jurkat cells (positive control) and CEM cells (negative control), HUASMCs limited expressed mIL-6R. Conclusion:IL-6 may induce HUASMCs osteogenic differentiation and calcification mainly via the sIL-6R-mediated trans-signaling pathway.
ABSTRACT
Objective:To establish an animal model of chronic systemic inflammation with long-term high expression of circulating IL-6 by introducing exogenous IL-6 gene transfer vector.Methods:Recombinant murine IL-6-encoding adeno-associated virus (AAV-IL-6) was constructed. Twenty-one 24-week-old male C57BL/6J mice were randomly divided into three groups with seven in each group: AAV-IL-6 group, vector control (AAV-ctrl) group and blank control group. At 0, 8 and 16 weeks of intervention, the mice in the three groups were injected with AAV-IL-6 (100 μl 0.5×10 10 vp/ml), unloaded AAV (100 μl 0.5×10 10 vp/ml) and the same volume of saline in the tail vein, respectively. IL-6 levels in mouse serum were measured by ELISA. The general condition of mice was observed and blood routine tests were performed. Changes in blood biochemical parameters and C-reactive protein (CRP) levels were detected. At the end of 24-week intervention, the mice were sacrificed and the myocardium, liver, spleen, quadriceps femoris, knee joint and middle femur were taken for HE staining. Results:At 4, 8, 16 and 24 weeks after intervention, serum IL-6 levels were (75.41-169.28) pg/ml in the AAV-IL-6 group, while in the two control groups, the levels were below the lower limit of detection (7.8 pg/ml). At 24 weeks after intervention, the body weight of mice in the AAV-IL-6 group was significantly lower than that of mice in the two control groups; the neutrophil counts and CRP level in the AAV-IL-6 group were higher than those in the two control groups, while the levels of albumin, creatinine, triglyceride and cholesterol were lower than those in the two control groups. There were no differences in the aforementioned parameters between the two control groups. Compared with the blank control group, both AAV-IL-6 and AAV-ctrl groups showed increased lymphocyte counts. All mice had normal liver and kidney functions at the end of intervention. Histopathological findings indicated that the mice in the AAV-IL-6 group had focal infiltration of lymphocytes in the central venous area of the liver and around the myocardial and the skeletal muscle fibers, diffuse infiltration of multinucleated giant cells in the spleen, atrophic skeletal muscle, disorganized growth plate, reduced chondrocyte hypertrophic zone, thinner bone cortex and trabecular, and reduced osteoid. There were no histopathological changes in mice of the two control groups.Conclusions:Repeated tail vein injection of AAV-IL-6 could achieve long-term high expression of circulating IL-6 in mice, which manifested the phenotype of chronic systemic inflammation in preliminary detection and provided a safe, effective and simply accessible animal model for related studies.