Wehrhan Falk, Amann Kerstin, Möbius Patrick, Weber Manuel, Preidl Raimund, Ries Jutta, Stockmann Phillip
Department of Oral and Maxillofacial Surgery, Friedrich-Alexander-University of Erlangen, Glueckstrasse 11, 91054, Erlangen, Germany,
Clin Oral Investig. 2015 Jul;19(6):1289-98. doi: 10.1007/s00784-014-1354-7. Epub 2014 Dec 3.
Site-specific suppression of bone remodelling has been implicated in bisphosphonate-(BP)-related osteonecrosis of the jaws (BRONJ). Due to the origin of jaw bone from cranial neural crest, osseous differentiation is regulated specifically by the antagonizing BMP-2-downstream-transcription factors Msx-1 and Dlx-5. Osteopontin has been implicated in bone remodelling and angiogenesis. The osteoblast and osteoclast progenitor proliferation mediating Msx-1 has been demonstrated to be suppressed in BRONJ. In vitro BPs were shown to increase Dlx-5 and to suppress osteopontin expression. This study targeted Dlx-5 and osteopontin in BRONJ-related and BP-exposed jaw bone compared with healthy jaw bone samples at protein- and messenger RNA (mRNA) level, since increased Dlx-5 and suppressed osteopontin might account for impaired bone turnover in BRONJ.
Fifteen BRONJ-exposed, 15 BP-exposed and 20 healthy jaw bone samples were processed for real-time reverse transcription polymerase chain reaction (RT-PCR) and for immunohistochemistry. Targeting Dlx-5, osteopontin and glyceraldehyde 3-phosphate dehydrogenase mRNA was extracted, quantified by the LabChip-method, followed by quantitative RT-PCR. For immunohistochemistry, an autostaining-based alkaline phosphatase antialkaline phosphatase (APAPP) staining kit was used. Semiquantitative assessment was performed measuring the ratio of stained cells/total number of cells (labelling index, Bonferroni adjustment).
The labelling index was significant decreased for osteopontin (p < 0.017) and significantly increased for Dlx-5 (p < 0.021) in BRONJ samples. In BRONJ specimens, a significant fivefold decrease in gene expression for osteopontin (p < 0.015) and a significant eightfold increase in Dlx-5 expression (p < 0.012) were found.
BRONJ-related suppression of bone turnover is consistent with increased Dlx-5 expression and with suppression of osteopontin. The BP-related impaired BMP-2-Msx-1-Dlx-5 axis might explain the jaw bone specific alteration by BP.
The findings of this study help to explain the restriction of RONJ to craniofacial bones. BRONJ might serve as a model of disease elucidating the specific signal transduction of neural crest cell-derived bone structures in health and disease.
双膦酸盐相关颌骨坏死（BRONJ）与骨重塑的位点特异性抑制有关。由于颌骨起源于颅神经嵴，骨分化由拮抗骨形态发生蛋白2（BMP-2）下游转录因子Msx-1和Dlx-5特异性调节。骨桥蛋白与骨重塑和血管生成有关。在BRONJ中，介导Msx-1的成骨细胞和破骨细胞祖细胞增殖受到抑制。体外研究表明，双膦酸盐可增加Dlx-5表达并抑制骨桥蛋白表达。本研究在蛋白质和信使核糖核酸（mRNA）水平上，将BRONJ相关及双膦酸盐暴露的颌骨中的Dlx-5和骨桥蛋白作为研究对象，并与健康颌骨样本进行比较，因为Dlx-5增加和骨桥蛋白抑制可能是BRONJ中骨转换受损的原因。
对15个BRONJ暴露样本、15个双膦酸盐暴露样本和20个健康颌骨样本进行实时逆转录聚合酶链反应（RT-PCR）和免疫组织化学检测。提取靶向Dlx-5、骨桥蛋白和甘油醛-3-磷酸脱氢酶的mRNA，采用LabChip方法进行定量，随后进行定量RT-PCR。免疫组织化学采用基于自动染色的碱性磷酸酶抗碱性磷酸酶（APAPP）染色试剂盒。通过测量染色细胞与细胞总数的比例（标记指数，Bonferroni校正）进行半定量评估。
BRONJ样本中骨桥蛋白的标记指数显著降低（p < 0.017），Dlx-5的标记指数显著升高（p < 0.021）。在BRONJ标本中发现，骨桥蛋白基因表达显著降低了5倍（p <
