Abstract:

BACKGROUND: The regulatory role of extracellular signal regulated kinase 1/2 (ERK1/2) and nuclear factor kappa B (NF-κB) signal pathways in the osteogenic differentiation of MC3T3-E1 cells subjected to mechanical strain remains unclear.
OBJECTIVE: To investigate the effects of ERK1/2 and NF-kB signal pathway on alkaline phosphatase, type Ⅰ collagen, osteocalcin and interleukin-6 expression in osteoblasts in response to mechanical strain, and to explore the regulatory effects of ERK1/2 and NF-kB signal pathway on osteoblast differentiation.
METHODS: MC3T3-E1 cells cultured in vitro were separately treated with ERK1/2 pathway specific inhibitor PD098059 and NF-kB pathway inhibitor PDTC for 30 minutes, and subjected to12% elongation for 24 hours. Normal cells and cells along loading 12% mechanical strain for 24 hours were considered as controls. Enzyme linked immunosorbent assay and real-time PCR were utilized to detect alkaline phosphatase activities, type Ⅰ collagen, osteocalcin and interleukin-6 mRNA expression before and after cell loading.
RESULTS AND CONCLUSION: Under 12% mechanical strain, alkaline phosphatase, type I collagen, and interleukin-6 expression was regulated by ERK1/2 signal pathway in MC3T3-E1 cells, but osteocalcin gene expression was not affected by ERK1/2 pathway. NF-kB signal pathway inhibitor PDTC significantly suppressed alkaline phosphatase activities in MC3T3-E1 cells under mechanical strain, and inhibited interleukin-6 gene expression. However, type I collagen and osteocalcin gene expression was not affected by NF-kB signal pathway. Results suggested that mechanical strain affected osteogenic differentiation and relevant gene expression in MC3T3-E1 cells by ERK1/2 and NF-kB signal pathway.

Key words: stress, mechanical, osteoblasts, NF-kB, alkaline phosphatase, type Ⅰ collagen, interleukin-6