Osteoblast is necessary for IGF-I to promote bone resorption by osteoclast / 中华内分泌代谢杂志

ABSTRACT

Objective To study whether osteoblast is necessary for IGF-Ⅰ to promote bone resorption by osteoclast.Methods Mouse MC3T3 osteoblast cells and mature osteoclasts induced by RANKL were cultured in vitro.These osteoblasts and osteoclasts were subjected to treatment with recombinant human insulin-like growth factor-1 (rhIGF-Ⅰ),and the activation of IGF-Ⅰ receptor was verified by Western blotting.Thereafter,osteoclasts were cultured individually or co-cultured with osteoblast,in the absence or presence of rhIGF-Ⅰ.Osteoclast proliferation and apoptosis were observed by MTT colorimetric assay and flow cytometry.Cathepsin K gene expression was detected by real-time PCR; bone adsorption activity of osteoclast was determined by resorption pits formation on calf cortex slice with toluidine blue staining.Results Western blotting result confirmed that rhIGF-Ⅰ could effectively activate IGF-Ⅰ receptors either in osteoblast or osteoclast.In co-cultured group,in the presence of rhIGF-Ⅰ osteoclast showed inhibited apoptosis,enhanced proliferation and up-regulated cathepsin K expression (P ＜ 0.05).The functional experiment revealed that osteoclasts collected from IGF-Ⅰ treated co-cultured group resulted in more resorption pits formation (P ＜ 0.05); rhIGF-Ⅰ did not show any significant effect on the individually cultured osteoclasts.Conclusion Osteoblast is necessary for osteoclast induced bone resorption resulting from IGF-Ⅰ treatment.