The effect of gravitational alteration on the formation and activation of osteoclast.

骨破坏在空间中进行。据报道，这种现象依赖于成骨细胞活性的降低。但破骨细胞的活性是否与空间环境下骨丢失有关尚不清楚，本研究主要探讨了超重力和微重力环境下破骨细胞的形成和激活。分别用离心法和回转器培养法获得超重力和准微重力，观察破骨细胞的形成。超重力和准微重力对活性维生素D_3诱导的破骨细胞形成无影响，甲状旁腺激素，在小鼠骨髓培养中的三尖杉酯碱。从RAW276.4细胞诱导破骨细胞也不受超重力和准微重力的影响。超重力对大鼠胎骨的骨吸收活性无影响。因此，在破骨细胞的形成和激活方面没有观察到重力改变的变化，已知超重力暴露会增加成骨细胞的功能，相反，已知空间中的微重力会减少。我们首次推测破骨细胞在骨破坏中也与成骨细胞一样起重要作用。但是，我们的研究结果表明，成骨细胞的功能下降是重要的，破骨细胞的作用是次要的。

Bone destruction proceeds in the space. It is reported that this phenomenon depends on the decrease of the osteoblastic activity. But it is not known whether the osteoclastic activity is important or not for the bone loss in the space.This study focused on the formation and the activation of osteoclasts induced by the exposure of the hypergravity or microgravity. Hypergravity and quasi-microgravity were obtained by the centrifugation and by the clinostat culture, respectively.The formation of osteoclasts were observed in the following two methods, the first is the mouse bone marrow culture and the second is the culture of RAW276.4 cells in which the osteoclasts are induced by the RANKL.Both hypergravity and quasi-microgravity had no effects on the formation of osteoclasts induced by active vitaminD_3, parathyroid hormone, prostaglandins in the mouse bone marrow culture. The induction of osteoclasts from RAW276.4 cells were also not influenced by both hypergravity and quasi-microgravity. Hypergravity had no effects on the bone-resorbing activity of rat fetal bone. Therefore, no changes were observed in the formation and activation of osteoclasts by the gravitational alteration.Exposure of hypergravity is known to increase the function of osteoblasts and, on the contrary, microgravity in the space is known to decrease. We first speculated that the osteoclasts also have the important role on the bone destruction as well as the osteoblasts in the space. But, our results shows that decreased function of osteoblasts are important for the bone loss in the space and the osteoclasts has the minor role.