Osteocytes, not Osteoblasts or Lining Cells, are the Main Source of the RANKL Required for Osteoclast Formation in Remodeling Bone.
Osteocytes, not Osteoblasts or Lining Cells, are the Main Source of the RANKL Required for Osteoclast Formation in Remodeling Bone.
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DOI：
10.1371/journal.pone.0138189
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
O'Brien CA
中科院分区：
文献类型：
--
作者：
Xiong J;Piemontese M;Onal M;Campbell J;Goellner JJ;Dusevich V;Bonewald L;Manolagas SC;O'Brien CA
核因子κ B配体的细胞因子受体激活因子（RANKL）由Tnfsf11基因编码，对破骨细胞的形成至关重要，先前的研究表明，使用Dmp1-Cre转基因删除Tnfsf11基因可使松质骨中破骨细胞的形成减少70%以上。然而，在这些研究中使用的Dmp1-Cre转基因导致骨细胞、成骨细胞和衬细胞重组，这使得尚不清楚这些细胞类型中的一种或多种是否产生松质骨中破骨细胞形成所需的RANKL。由于成骨细胞、骨细胞和衬细胞具有不同的位置和功能，因此区分哪些细胞类型是RANKL的来源对于理解骨重塑的编排至关重要。为了区分这些可能性，我们现在创建了在Sost基因调控元件的控制下表达Cre重组酶的转基因小鼠，Sost基因在骨细胞中表达，而不是在小鼠骨的成骨细胞或衬细胞中表达。通过将Sost-Cre转基因小鼠与分别表达tdTomato荧光蛋白或LacZ的tdTomato和R26R Cre报告基因小鼠杂交，证实了Sost-Cre转基因小鼠在表达Cre重组酶或其后代的细胞中具有骨细胞活性，而不是成骨细胞或衬细胞。Sost-Cre小鼠中Tnfsf11基因的缺失导致松质骨中破骨细胞数量减少三倍，松质骨量增加，模拟了使用Dmp1-Cre转基因缺失Tnfsf11基因的小鼠的骨骼表型。这些结果表明，骨细胞，而不是成骨细胞或衬里细胞，是在重塑松质骨中破骨细胞形成所需的RANKL的主要来源。
The cytokine receptor activator of nuclear factor kappa B ligand (RANKL), encoded by the Tnfsf11 gene, is essential for osteoclastogenesis and previous studies have shown that deletion of the Tnfsf11 gene using a Dmp1-Cre transgene reduces osteoclast formation in cancellous bone by more than 70%. However, the Dmp1-Cre transgene used in those studies leads to recombination in osteocytes, osteoblasts, and lining cells making it unclear whether one or more of these cell types produce the RANKL required for osteoclast formation in cancellous bone. Because osteoblasts, osteocytes, and lining cells have distinct locations and functions, distinguishing which of these cell types are sources of RANKL is essential for understanding the orchestration of bone remodeling. To distinguish between these possibilities, we have now created transgenic mice expressing the Cre recombinase under the control of regulatory elements of the Sost gene, which is expressed in osteocytes but not osteoblasts or lining cells in murine bone. Activity of the Sost-Cre transgene in osteocytes, but not osteoblast or lining cells, was confirmed by crossing Sost-Cre transgenic mice with tdTomato and R26R Cre-reporter mice, which express tdTomato fluorescent protein or LacZ, respectively, only in cells expressing the Cre recombinase or their descendants. Deletion of the Tnfsf11 gene in Sost-Cre mice led to a threefold decrease in osteoclast number in cancellous bone and increased cancellous bone mass, mimicking the skeletal phenotype of mice in which the Tnfsf11 gene was deleted using the Dmp1-Cre transgene. These results demonstrate that osteocytes, not osteoblasts or lining cells, are the main source of the RANKL required for osteoclast formation in remodeling cancellous bone.