OSTEOBLAST AND PTH/PTHRP BONE RESORPTION

成骨细胞或成骨细胞样细胞是其主要成分 甲状旁腺激素和甲状旁腺激素相关蛋白 绑在骨头里。我们假设成骨细胞衍生因子是 因此，甲状旁腺激素和甲状旁腺素rP诱导的局部介质至关重要 骨吸收。这一假说的一个推论是， PTH和PTHrP在成骨细胞上的作用可能有助于解释 这两种激素在体内的作用不同。为了追求这一点 假说，这两种激动剂对成骨细胞来源的影响 可以1)激活成熟破骨细胞或2)刺激的因素 将检查破骨前细胞的募集情况。 我们观察到甲状旁腺素和甲状旁腺素处理的成骨细胞释放一种可溶性的 骨吸收活动。这一活性已被部分纯化并 可通过分离的破骨细胞直接刺激吸收(下 PTHrP处于非活动状态的条件)。这种材料将被提纯到 同质性，以获得初级结构信息。氨基酸 序列信息将用于合成寡核苷酸探针 用于筛选Saos-2cDNA文库。基于我们之前的工作， 证明甲状旁腺素诱导成骨细胞释放GM-CSF，该分子 将作为成骨细胞衍生因子的一个例子进行研究，这种因子可能 规范破骨细胞募集。潜在的分子机制 甲状旁腺素/甲状旁腺素刺激破骨细胞释放GM-CSF将被检测 GM-CSF中和血清对甲状旁腺激素/甲状旁腺素rP诱导的影响 胎鼠长骨和小鼠跖骨的吸收实验。 我们最近在成年大鼠体内发现了脑脊液-1受体(c-FMS) 破骨细胞。此外，在初步研究中，我们已确定- GM-CSF对该受体的调节提示一种重要的相互作用 这两种集落刺激因子对破骨细胞的调节作用 生物学。这些观察将使用免疫细胞化学进行 技术和原位杂交。具体来说，我们将研究 GM-CSF对c-FMS的影响是否发生在 转录或翻译。 最后，使用大鼠胰岛素瘤细胞的哺乳动物表达系统已经 使用PTHrP的三个可用的cDNA克隆进行了开发。这个 氨基末端纯化的重组PTHrP对信号的影响 吸收细胞因子的转导机制和释放， 将对成骨细胞进行研究。总体而言，这些研究应该 从而对甲状旁腺素和甲状旁腺素的细胞机制有更精确的了解 PTHrP诱导骨吸收，应该会导致更清晰的图像 这些化合物在生理条件下的作用以及 矿物质动态平衡失调。

The osteoblast or an osteoblast-like cell is the principal to which parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) bind in bone. We hypothesize that osteoblast-derived factors are therefore critically important local mediators of PTH-and PTHrP-induced bone resorption. A corollary to this hypothesis is that differences in the actions of PTH and PTHrP on osteoblasts may help explain the different in vivo effects of these two hormones. To pursue this hypothesis, the effects of these two agonists on osteoblasts-derived factors which may 1) activate mature osteoclasts or 2) stimulate recruitment of pre-osteoclasts will be examined. We have observed that PTH and PTHrP-treated osteoblasts release a soluble bone-resorbing activity. This activity has been partially purified and can directly stimulate resorption by isolated osteoclasts (under conditions where PTHrP is inactive). This material will be purified to homogeneity to obtain primary structural information. Amino-acid sequence information will be used to synthesize oligonucleotide probes for screening an Saos-2cDNA library. Based on our previous work, demonstrating PTH-induce GM-CSF release from osteoblasts, this molecule will be studied as an example of an osteoblast-derived factor which may regulate osteoclast recruitment. The molecular mechanisms underlying PTH/PTHrP-stimulated release of GM-CSF from osteoclast will be examining the effects of neutralizing antisera to GM-CSF on PTH/PTHrP-induced resorption in the fetal rat long-bone and mouse metatarsal assays. We have very recently identified CSF-1 receptors (c-fms) in mature rat osteoclasts. Further, in preliminary studies we have identified down- regulation of this receptor by GM-CSF suggesting an important interaction between these two colony-stimulating factors in regulating osteoclast biology. These observations will be pursued using immunocytochemical techniques and in situ hybridization. Specifically, we will study whether the effect of GM-CSF on c-fms occurs at the level of transcription or translation. Finally, a mammalian expression system employing rat insulinoma cells has been developed using the three available cDNA clones for PTHrP. The effects of amino-terminal purified recombinant PTHrP on signal transduction mechanisms in, and release of resorptive cytokines from, osteoblasts will be studied. In the aggregate, these studies should allow a more precise picture of the cellular mechanisms by which PTH and PTHrP induce resorption in bone and should lead to a clearer picture of how these compounds act under physiologic conditions as well as those of disturbed mineral homeostasis.