IGF—I对破骨细胞骨吸收的促进作用依赖于成骨细胞的协同

Osteoblast is necessary for IGF- I to promote bone resorption by osteoclast

目的探讨胰岛素样生长因子I（IGF-I）对破骨细胞骨吸收的促进作用是否需要成骨细胞的协同。方法体外培养MC3T3小鼠成骨细胞及NF—KB受体的配体（receptor activator o fNF—KBligand，RANKL）诱导分化成熟的破骨细胞，分别给予重组人胰岛素样生长因子I（rhIGF—I）进行干预，Western印迹检测IGF—I受体的活化情况。以0、10ng／ml的rhIGF—I直接干预破骨细胞或与成骨细胞在Transwell双层培养板中共培养的破骨细胞，MTT法测定破骨细胞增殖；流式细胞仪检测破骨细胞凋亡率：实时PCR检测组织蛋白酶K基因的表达。将不同方式干预的破骨细胞接种在骨磨片上，光镜观察骨吸收陷窝的形成。结果在成骨细胞、破骨细胞表面均检测到可被IGF—I激活的IGF—I受体。仅在成骨细胞、破骨细胞共培养时rhIGF—I能够促进破骨细胞活细胞的增殖（P〈0．05）；抑制破骨细胞的凋亡（P〈0．05）；上调组织蛋白酶K基因的表达（P〈0．05）；增加骨吸收陷窝的数量及面积。IGF—I对单独培养的破骨细胞则作用不明显。结论IGF—I对破骨细胞骨吸收的促进作用需要成骨细胞的协同。

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, osteoelasts were cultured individually or co-cuhured with osteoblast, in the absence or presence of rhlGF- I . Osteoelast proliferation and apoptosis were observed by MTF 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 rhlGF- 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-cuhured 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.