Osteocytes Acidify Their Microenvironment in Response to PTHrP In Vitro and in Lactating Mice In Vivo.
Osteocytes Acidify Their Microenvironment in Response to PTHrP In Vitro and in Lactating Mice In Vivo.
复制标题
DOI：
10.1002/jbmr.3167
复制
发表时间：
2017-08
期刊：
影响因子：
--
通讯作者：
Bonewald LF
中科院分区：
文献类型：
--
作者：
Jähn K;Kelkar S;Zhao H;Xie Y;Tiede-Lewis LM;Dusevich V;Dallas SL;Bonewald LF
骨细胞似乎在几分钟内动员钙，以响应PTH注射，我们以前已经表明，骨细胞在哺乳期间通过激活PTH 1型受体去除其骨间隙基质。骨细胞动员钙的机制尚不清楚，但我们假设其分子组成可能与破骨细胞相似。在这里，我们表明，使用IDG-SW 3细胞，ATP 6V 0 D2，破骨细胞中的空泡ATP酶的重要组成部分，和其他基因与骨细胞骨吸收增加成骨细胞分化成骨细胞。此外，PTHrP增加ATP 6V 0 D2表达并诱导原代骨细胞产生质子，这被巴弗洛霉素（一种空泡ATP酶抑制剂）阻断。这些体外质子测量提出了骨细胞在酸性环境中生存能力的问题。有趣的是，与成骨细胞和成纤维细胞相比，骨细胞在体外pH低至5时显示出增强的活力。为了研究骨细胞的体内酸化，给低钙饮食的处女和哺乳期CD 1小鼠注射pH指示剂染料吖啶橙子，并通过共聚焦显微镜对它们的骨细胞腔隙-小管系统进行成像。与未交配动物相比，在哺乳期动物中观察到较低的pH值。此外，还使用了一种新型转基因小鼠系，该小鼠系带有GFPtpz标记的胶原蛋白α2（I）链。在哺乳期小鼠的整个骨基质中观察到荧光减少，而不是仅在月旁基质中预期的GFP荧光减少。基于我们的实验显示GFP在体外的淬灭，我们提出，在哺乳期小鼠中观察到的GFP荧光的减少是由于由骨细胞产生的酸性pH值的GFP淬灭。总之，这些研究结果提供了新的机制洞察骨细胞如何从他们的acunar/pericanalicular矩阵通过主动酸化的微环境，并显示骨细胞，破骨细胞，是耐酸性的负面影响的活力。
Osteocytes appear to mobilize calcium within minutes in response to PTH injections and we have previously shown that osteocytes remove their perilacunar matrix during lactation through activation of the PTH type 1 receptor. Mechanisms utilized by osteocytes to mobilize calcium are unknown but we hypothesized that the molecular components may be similar to those used by osteoclasts. Here we show, using IDG-SW3 cells that ATP6V0D2, an essential component of vacuolar ATPase in osteoclasts, and other genes associated with osteoclastic bone resorption increase with osteoblast to osteocyte differentiation. Furthermore, PTHrP increases ATP6V0D2 expression and induces proton generation by primary osteocytes, which is blocked by bafilomycin, a vacuolar ATPase inhibitor. These in vitro proton measurements raised the question of osteocyte viability in an acidic environment. Interestingly, osteocytes, showed enhanced viability at pH as low as 5 compared to osteoblasts and fibroblasts in vitro. To study in vivo acidification by osteocytes, virgin and lactating CD1 mice on a low calcium diet were injected with the pH indicator dye, acridine orange, and their osteocyte lacuno-canalicular system imaged by confocal microscopy. Lower pH was observed in lactating compared to virgin animals. In addition, a novel transgenic mouse line with a GFPtpz-tagged collagen α2(I) chain was used. Instead of the expected reduction in GFP-fluorescence only in the perilacunar matrix, reduced fluorescence was observed in the entire bone matrix of lactating mice. Based on our experiments showing quenching of GFP in vitro, we propose that the observed reduction in GFP fluorescence in lactating mice is due to quenching of GFP by the acidic pH generated by osteocytes. Together these findings provide novel mechanistic insight into how osteocytes remove calcium from their perilacunar/pericanalicular matrices through active acidification of their microenvironment and show that osteocytes, like osteoclasts, are resistant to the negative effects of acid on viability.
登录
查看更多内容
影响因子：
6.2
作者：
Kitase, Yukiko;Barragan, Leonardo;Qing, Hai;Kondoh, Shino;Jiang, Jean X.;Johnson, Mark L.;Bonewald, Lynda F.
通讯作者：
Bonewald, Lynda F.
影响因子：
6.2
作者：
Kogawa, Masakazu;Wijenayaka, Asiri R.;Atkins, Gerald J.
通讯作者：
Atkins, Gerald J.
影响因子：
6.2
作者：
Kato, Y;Boskey, K;Bonewald, LF
通讯作者：
Bonewald, LF
影响因子：
17.1
作者：
Milovanovic, Petar;Zimmermann, Elizabeth A.;Busse, Bjoern
通讯作者：
Busse, Bjoern
影响因子：
4.1
作者：
Sano, Hiroshige;Kikuta, Junichi;Ishii, Masaru
通讯作者：
Ishii, Masaru