Wada S, Udagawa N, Nagata N, Martin T J, Findlay D M
St. Vincent's Institute of Medical Research, Melbourne, Australia.
Endocrinology. 1996 Mar;137(3):1042-8. doi: 10.1210/endo.137.3.8603572.
We have reported that short calcitonin (CT) treatment of mature mouse osteoclast-like cells (OCLs) in culture induced prolonged down-regulation of the CT receptor (CTR) and desensitization to CT rechallenge, at the level of adenylate cyclase activity. In this study, we have extended those studies to examine the bone resorbing activity of OCLs pretreated with CT. OCLs, which formed on gelled type I collagen, were pretreated with salmon CT (sCT)(10(-9)M, 1 h) and 24 h later were replated onto plastic dishes or dentine slices after removal from the gel by collagenase digestion. The number and population of either mononuclear or multinuclear OCLs that adhere to either surface was not affected by sCT pretreatment. It was found that OCLs pretreated with sCT regained reduced but significant bone resorbing capacity, which was quantitated as the surface area resorbed by OCLs on dentine slices. However, compared with control, the number of resorption pits produced by sCT- pretreated OCLs was slightly reduced, and the total pit area was decreased by approximately 40-50%. The distribution of individual pit sizes was altered by sCT-pretreatment so that the number of larger pits was predominantly reduced, suggesting that short sCT treatment may produce a long lasting decrease in osteoclast mobility. sCT was able to inhibit bone resorption activity of CT-pretreated OCLs (ED50:10(-13)-10(-12)M). Importantly, the ED50 of sCT inhibition of bone resorption in sCT-pretreated OCLs was approximately 100-fold greater than for control, indicating resistance of the OCLs to CT rechallenge. Consistent with these results, treatment of OCLs with sCT greatly decreased the expression of CTR messenger RNA, whereas no significant effect was observed on the tartrate-resistant acid phosphatase messenger RNA expression, a marker of resorptive capacity of osteoclasts. These results indicate, therefore, that an important component of escape of osteoclastic resorption from CT inhibition is CT resistance of mature osteoclasts, which regain bone resorbing function.
我们曾报道，在培养中用短时间的降钙素（CT）处理成熟小鼠破骨细胞样细胞（OCLs），可在腺苷酸环化酶活性水平上诱导CT受体（CTR）的长期下调以及对CT再次刺激的脱敏。在本研究中，我们扩展了这些研究，以检测经CT预处理的OCLs的骨吸收活性。在凝胶化的I型胶原上形成的OCLs，先用鲑鱼降钙素（sCT）（10⁻⁹M，1小时）预处理，24小时后通过胶原酶消化从凝胶中去除，再接种到塑料培养皿或牙本质切片上。附着在任何一种表面的单核或多核OCLs的数量和群体不受sCT预处理的影响。结果发现，经sCT预处理的OCLs恢复了降低但仍显著的骨吸收能力，这通过OCLs在牙本质切片上吸收的表面积来定量。然而，与对照相比，经sCT预处理的OCLs产生的吸收陷窝数量略有减少，总陷窝面积减少了约40 - 50%。sCT预处理改变了单个陷窝大小的分布，使得较大陷窝的数量主要减少，这表明短时间的sCT处理可能会使破骨细胞的迁移能力产生持久下降。sCT能够抑制经CT预处理的OCLs的骨吸收活性（半数有效剂量：10⁻¹³ - 10⁻¹²M）。重要的是，sCT对经sCT预处理的OCLs骨吸收抑制的半数有效剂量比对对照的约大100倍，表明OCLs对CT再次刺激具有抗性。与这些结果一致，用sCT处理OCLs大大降低了CTR信使核糖核酸的表达，而对破骨细胞吸收能力的标志物抗酒石酸酸性磷酸酶信使核糖核酸的表达未观察到显著影响。因此，这些结果表明，破骨细胞吸收从CT抑制中逃逸的一个重要组成部分是成熟破骨细胞的CT抗性，其恢复了骨吸收功能。
