Loss of Dkk-1 in Osteocytes Mitigates Alveolar Bone Loss in Mice With Periodontitis
Loss of Dkk-1 in Osteocytes Mitigates Alveolar Bone Loss in Mice With Periodontitis
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DOI：
10.3389/fimmu.2019.02924
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发表时间：
2019-12-10
影响因子：
7.3
通讯作者：
Thiele, Sylvia
中科院分区：
文献类型：
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作者：
Goes, Paula;Dutra, Caio;Thiele, Sylvia
背景：牙周炎是一种非常普遍的由感染引发的炎症性疾病，可导致骨质流失。炎症通过破骨细胞引起骨吸收，也通过增加Dickkopf-1 （Dkk-1）抑制骨形成，Dickkopf-1是Wnt信号的抑制剂。在这里，我们验证了骨细胞Dkk-1是牙周炎诱导的牙槽骨丢失（ABL）发病机制的关键因素的假设。方法：在骨细胞中特异性缺失Dkk-1的12周龄雌性小鼠(Dkk-1(fl/fl)；Dmp1:Cre)进行实验性牙周炎（EP）治疗。cre阴性的幼崽作为对照组。在左上第二磨牙周围结扎诱导EP，对侧作为对照。11天后处死小鼠，切除上颌骨进行显微ct和组织学分析。采用实时荧光定量PCR法检测上颌组织中Dkk-1、Runx2、骨钙素、OPG、RANKL、RANKL/OPG比值、LEF-1、TCF-7 mRNA的表达，牙龈组织中TNF、IL-1 mRNA的表达。采集血样，采用ELISA法检测Dkk-1、CTX和P1NP。结果：与cre阴性的EP小鼠相比，骨细胞中Dkk-1的缺失可预防EP小鼠的ABL。Micro-CT分析显示EP Dkk-1（fl/fl）骨丢失显著减少（-28.5%）；Dmp1：与对照组相比，cre1阳性小鼠。与cre阴性对照相比，EP后小鼠的牙槽骨体积、骨矿物质密度、小梁数量和小梁厚度均有所增加。Dkk-1（fl/fl）在上颌骨的局部表达和血清水平均降低；Dmp1: EP阳性小鼠。经EP处理的转基因小鼠血清中P1NP升高，CTX-I水平降低，TCF-7表达升高。组织学分析显示，cree阳性EP动物的炎症浸润较少，牙龈中TNF和IL-1表达减少，破骨细胞减少。此外，在EP小鼠中，由于颌骨Runx2和骨钙素的表达增加，RANKL的表达减少，Dkk-1的骨细胞缺失促进了骨形成。结论：综上所述，来自骨细胞的Dkk-1在牙周炎ABL中起着至关重要的作用。
Background: Periodontitis is a highly prevalent infection-triggered inflammatory disease that results in bone loss. Inflammation causes bone resorption by osteoclasts, and also by suppression of bone formation via increase of Dickkopf-1 (Dkk-1), an inhibitor of Wnt signaling. Here, we tested the hypothesis that osteocytic Dkk-1 is a key factor in the pathogenesis of periodontitis-induced alveolar bone loss (ABL). Methods: Twelve-week-old female mice with a constitutive deletion of Dkk-1 specifically in osteocytes (Dkk-1(fl/fl);Dmp1:Cre) were subjected to experimental periodontitis (EP). Cre-negative littermates served as controls. EP was induced by placing a ligature around the upper 2nd left molar, the contralateral side was used as control. Mice were killed after 11 days and maxillae removed for micro-CT and histological analyses. The mRNA expression of Dkk-1, Runx2, Osteocalcin, OPG, RANKL, RANKL/OPG ratio, LEF-1, and TCF-7 were assessed in maxillae, while mRNA expressions of TNF and IL-1 were evaluated on gingiva using real-time PCR. Blood samples were collected for Dkk-1, CTX, and P1NP measurement by ELISA. Results: The deletion of Dkk-1 in osteocytes prevented ABL in mice with EP, compared to Cre-negative control mice with EP. Micro-CT analysis showed a significant reduction of bone loss (-28.5%) in EP Dkk-1(fl/fl);Dmp1:Cre-positive mice compared to their littermate controls. These mice showed a greater alveolar bone volume, bone mineral density, trabecular number, and trabecular thickness after EP when compared to the Cre-negative controls. The local expression in maxillae as well as the serum levels of Dkk-1 were reduced in Dkk-1(fl/fl);Dmp1:Cre-positive mice with EP. The transgenic mice submitted to EP showed increase of P1NP and reduction of CTX-I serum levels, and increase of TCF-7 expression. Histological analysis displayed less inflammatory infiltrates, a reduction of TNF and IL-1 expressions in the gingiva and fewer osteoclasts in Cre-positive animals with EP. Moreover, in mice with EP, the osteocytic deletion of Dkk-1 enhanced bone formation due to increased expressions of Runx2 and Osteocalcin and decreased expression of RANKL in maxillae. Conclusion: In summary, Dkk-1 derived from osteocytes plays a crucial role in ABL in periodontitis.