Babey Muriel, Wang Yongmei, Kubota Takuo, Fong Chak, Menendez Alicia, ElAlieh Hashem Z, Bikle Daniel D
Endocrine Research Unit, University of California, San Francisco, CA, USA.
J Bone Miner Res. 2015 Jun;30(6):1064-76. doi: 10.1002/jbmr.2433.
The primary goal of this study was to determine whether the IGF1R in mature osteoblasts and osteocytes was required for the catabolic actions of continuous parathyroid hormone (cPTH). Igf1r was deleted from male and female FVN/B mice by breeding with mice expressing cre recombinase under control of the osteocalcin promoter ((0CN) Igfr1(-/-) ). Littermates lacking the cre recombinase served as controls. PTH, 60 μg/kg/d, was administered continuously by Alzet minipumps for 4 weeks. Blood was obtained for indices of calcium metabolism. The femurs were examined by micro-computed tomography for structure, immunohistochemistry for IGF1R expression, histomorphometry for bone formation rates (BFR), mRNA levels by qPCR, and bone marrow stromal cell cultures (BMSC) for alkaline phosphatase activity (ALP(+) ), mineralization, and osteoblast-induced osteoclastogenesis. Whereas cPTH led to a reduction in trabecular bone volume/tissue volume (BV/TV) and cortical thickness in the control females, no change was found in the control males. Although trabecular BV/TV and cortical thickness were reduced in the (0CN) Igfr1(-/-) mice of both sexes, no further reduction after cPTH was found in the females, unlike the reduction in males. BFR was stimulated by cPTH in the controls but blocked by Igf1r deletion in the females. The (0CN) Igfr1(-/-) male mice showed a partial response. ALP(+) and mineralized colony formation were higher in BMSC from control males than from control females. These markers were increased by cPTH in both sexes, but BMSC from male (0CN) Igfr1(-/-) also were increased by cPTH, unlike those from female (0CN) Igfr1(-/-) . cPTH stimulated receptor activator of NF-κB ligand (RANKL) and decreased osteoprotegerin and alkaline phosphatase expression more in control female bone than in control male bone. Deletion of Igf1r blocked these effects of cPTH in the female but not in the male. However, PTH stimulation of osteoblast-driven osteoclastogenesis was blocked by deleting Igfr1 in both sexes. We conclude that cPTH is catabolic in female but not male mice. Moreover, IGF1 signaling plays a greater role in the skeletal actions of cPTH in the female mouse than in the male mouse, which may underlie the sex differences in the response to cPTH.
本研究的主要目的是确定成熟成骨细胞和骨细胞中的胰岛素样生长因子1受体（IGF1R）是否是持续甲状旁腺激素（cPTH）分解代谢作用所必需的。通过与在骨钙素启动子（（0CN）Igfr1（-/-））控制下表达cre重组酶的小鼠杂交，从雄性和雌性FVN/B小鼠中删除Igf1r。缺乏cre重组酶的同窝小鼠作为对照。通过Alzet微型泵连续4周给予60μg/kg/d的PTH。采集血液以检测钙代谢指标。通过微型计算机断层扫描检查股骨结构，通过免疫组织化学检测IGF1R表达，通过组织形态计量学检测骨形成率（BFR），通过qPCR检测mRNA水平，并通过骨髓基质细胞培养（BMSC）检测碱性磷酸酶活性（ALP（+））、矿化和破骨细胞诱导的成骨细胞生成。虽然cPTH导致对照雌性小鼠的小梁骨体积/组织体积（BV/TV）和皮质厚度降低，但对照雄性小鼠未发现变化。虽然两性的（0CN）Igfr1（-/-）小鼠的小梁BV/TV和皮质厚度均降低，但与雄性小鼠的降低不同，雌性小鼠在cPTH后未发现进一步降低。cPTH刺激对照小鼠的BFR，但在雌性小鼠中被Igf1r缺失阻断。（0CN）Igfr1（-/-）雄性小鼠表现出部分反应。对照雄性小鼠的BMSC中的ALP（+）和矿化集落形成高于对照雌性小鼠。这些标志物在两性中均被cPTH增加，但雄性（0CN）Igfr1（-/-）的BMSC也被cPTH增加，与雌性（0CN）Igfr1（-/-）的不同。与对照雄性骨相比，cPTH在对照雌性骨中更能刺激核因子κB受体激活剂配体（RANKL）并降低骨保护素和碱性磷酸酶表达。删除Igf1r可阻断cPTH在雌性小鼠中的这些作用，但在雄性小鼠中不能。然而，PTH对成骨细胞驱动的破骨细胞生成的刺激在两性中均被删除Igfr1阻断。我们得出结论，cPTH在雌性小鼠中具有分解代谢作用，而在雄性小鼠中没有。此外，IGF1信号在雌性小鼠中对cPTH的骨骼作用中比在雄性小鼠中发挥更大的作用，这可能是对cPTH反应存在性别差异的基础。
