Analysis of gp130-induced signals which regulate osteclast formation and function

在小鼠成骨细胞和脾细胞共培养中，可溶性白细胞介素-6受体（sIL-6R）的存在触发了gp130介导的细胞因子IL-6诱导的破骨细胞形成。然而，白细胞介素-11 （IL-11）和肿瘤抑制素M也使用gp130作为常见的信号换能器，在各自的可溶性受体缺失的情况下刺激破骨细胞的形成。我们研究了gp130介导的信号如何调节破骨细胞的形成和功能。(1) RT-PCR分析发现成骨细胞表达IL-11受体，但不表达IL-6受体。利用表达IL-6受体（IL-6R）的转基因小鼠，在小鼠脾细胞和成骨细胞共培养中发现，IL-6诱导的破骨细胞形成离不开成骨细胞中IL-6R的表达。(2)我们研究了IL-6和sIL-6R在类风湿关节炎（RA）患者关节破坏中的可能参与。RA患者滑膜中可见破骨细胞样多核细胞。与骨关节炎患者相比，RA患者的滑液中IL-6和sIL-6R的浓度显著升高。(3)将破骨细胞置于牙本质切片上，在24h内形成吸收坑。细胞因子如IL-6、IL-11和oncostatin M不影响破骨细胞的成窝活性。此外，在坑形成实验中加入抗小鼠gp130抗体不影响破骨细胞功能。(4) 1 α、25(OH)_2D_3、PTH和PGE_2等骨吸收因子刺激成骨细胞产生IL-11。抗小鼠gp130抗体抑制小鼠成骨细胞与脾细胞共培养后这些骨吸收因子诱导的破骨细胞形成。这些结果表明gp130介导的信号参与破骨细胞的形成，但不参与破骨细胞的功能。

Existence of soluble interleukin-6 receptors (sIL-6R) triggers osteoclast formation induced by IL-6, a gp130-mediated cytokine, in co-culture of mouse osteoblastic cells and spleen cells. However, interleukin-11 (IL-11) and oncostatin M,which also use gp130 as a common signal transducer, stimulated osteoclast formation in the absence of respective soluble type receptors. We have studied how gp130-mediated signals regulate osteoclast formation and function. (1) RT-PCR analysis revered that osteoblastic cells expressed receptors for IL-11 but not for IL-6. Using transgenic mouse expressing IL-6 receptors (IL-6R), it was shown that the expression of IL-6R in osteoblastic cells is indispensable for osteoclast formation induced by IL-6 in co-cultures of mouse spleen cells and osteoblastic cells. (2) We examined the possible involvement of IL-6 together with sIL-6R in joinjt disruption of rheumatoid arthritis (RA) patients. Osteoclast-like multinucleated cells were found in synovium of RA patients. Synovial fluids from RA patients contained significantly elevated concentrations of both IL-6 and sIL-6R in comparison with those from osteoarthritis patients. (3) When osteoclasts were placed on dentine slices, they formed resorption pits within 24hr. Cytokines such as IL-6, IL-11 and oncostatin M did not influence pit forming activity of osteoclasts. In addition, osteoclast function was not affected by adding anti-mouse gp130 antibody to the pit formation assay. (4) Bone-resorbing factors such as 1alpha, 25(OH)_2D_3, PTH and PGE_2 stimulated production of IL-11 by osteoblastic cells. Anti-mouse gp130 antibody inhibited osteoclast formation induced by these bone-resorbing factors in co-culture of mouse osteoblastic cells and spleen cells. These results suggest that signals mediated by gp130 are involved in osteoclast formation but not in osteoclast function.