间歇性甲状旁腺激素(iPTH)的给药对骨骼是合成代谢的。最近对培养的成骨细胞的研究表明,PHOSPHO1的表达是矿化启动所必需的骨特异性磷酸酶,受PTH调控。因此,这项研究试图确定对iPTH的骨合成代谢反应是否涉及调节Phospho1和其他对骨基质矿化至关重要的酶的表达。为了模仿iPTH治疗,原代鼠成骨细胞每48小时用50nMPTH攻击6小时,共8天(4个周期),共14天(7个周期)和20天(10个周期)。4个周期后,Phospho1和Smpd3的表达几乎完全被抑制,而需要10个周期来刺激Alpl表达的类似反应。探讨PHOSPHO1在PTH介导的成骨过程中的体内作用,在雄性野生型(WT)和Phospho1-/-小鼠中评估了14天和28天iPTH(80µg/kg/天)给药的效果.Phospho1、Alpl、在iPTH施用后,WT小鼠的股骨中Smpd3,Enpp1,Runx2和Trps1的表达增强,但在Phospho1-/-小鼠的股骨中保持不变。iPTH给药28天后,WT股骨的合成代谢反应大于Phospho1-/-小鼠。具体来说,皮质骨和骨小梁体积/总体积,以及皮质厚度,在iPTH处理的WT的股骨中增加,但在iPTH处理的Phospho1-/-小鼠中没有增加。在iPTH处理的WT小鼠中,小梁骨成骨细胞数量也增加,但在iPTH处理的Phospho1-/-小鼠中没有增加。Phospho1,Alpl,WT小鼠响应iPTH给药的Enpp1和Smpd3与它们对iPTH在骨骼中的有效合成代谢特性的贡献一致。此外,由于缺乏PHOSPHO1的小鼠对iPTH的合成代谢反应减弱,这表明iPTH的骨合成代谢作用至少部分是通过骨矿化过程介导的。
The administration of intermittent parathyroid hormone (iPTH) is anabolic to the skeleton. Recent studies with cultured osteoblasts have revealed that the expression of PHOSPHO1, a bone-specific phosphatase essential for the initiation of mineralisation, is regulated by PTH. Therefore, this study sought to determine whether the bone anabolic response to iPTH involves modulation of expression of Phospho1 and of other enzymes critical for bone matrix mineralisation. To mimic iPTH treatment, primary murine osteoblasts were challenged with 50 nM PTH for 6 h in every 48 h period for 8 days (4 cycles), 14 days (7 cycles) and 20 days (10 cycles) in total. The expression of both Phospho1 and
Smpd3 was almost completely inhibited after 4 cycles, whereas 10 cycles were required to stimulate a similar response in Alpl expression. To explore the in vivo role of PHOSPHO1 in PTH-mediated osteogenesis, the effects of 14- and 28-day iPTH (80 µg/kg/day) administration was assessed in male wild-type (WT) and Phospho1-/- mice. The expression of Phospho1, Alpl,
Smpd3, Enpp1, Runx2 and Trps1 expression was enhanced in the femora of WT mice following iPTH administration but remained unchanged in the femora of Phospho1-/- mice. After 28 days of iPTH administration, the anabolic response in the femora of WT was greater than that noted in Phospho1-/- mice. Specifically, cortical and trabecular bone volume/total volume, as well as cortical thickness, were increased in femora of iPTH-treated WT but not in iPTH-treated Phospho1-/- mice. Trabecular bone osteoblast number was also increased in iPTH-treated WT mice but not in iPTH-treated Phospho1-/- mice. The increased levels of Phospho1, Alpl, Enpp1 and
Smpd3 in WT mice in response to iPTH administration is consistent with their contribution to the potent anabolic properties of iPTH in bone. Furthermore, as the anabolic response to iPTH was attenuated in mice deficient in PHOSPHO1, this suggests that the osteoanabolic effects of iPTH are at least partly mediated via bone mineralisation processes.