研究牙髓干细胞（DPSC）对牙周炎中破骨细胞形成及牙槽骨再生的影响，并初步探索DPSC对小鼠破骨细胞的作用机制。

体外诱导小鼠骨髓单核细胞破骨分化，观察破骨细胞组（OC组）及其与DPSC共培养组（OC+DPSC组）的抗酒石酸酸性磷酸酶（TRAP）染色情况，实时荧光定量聚合酶链反应（PCR）检测破骨分化相关基因包括活化T细胞核因子（NFATc1）、基质金属蛋白酶9（MMP-9）及TRAP的表达差异。体内构建小鼠慢性牙周炎模型，通过微计算机体层摄影（micro-CT）扫描后三维重建，比较慢性牙周炎+0.9%氯化钠溶液注射组（NS组）和慢性牙周炎+DPSC注射组（DPSC组）釉牙骨质界至牙槽嵴顶（CEJ-ABC）距离，并对标本进行苏木精-伊红和TRAP染色，观察DPSC对小鼠破骨细胞及牙槽骨再生的影响。采用SPSS 20.0软件进行数据统计分析，采用独立样本t检验及校正t检验分析组间差异。

体外TRAP染色发现，与DPSC共培养明显抑制成熟破骨细胞形成，OC+DPSC组成熟破骨细胞均数（4.2 ± 0.2）少于OC组均数（6.8 ± 0.2），差异有统计学意义（t= 15.922，P<0.001）；破骨细胞表面积均数（0.046 ± 0.007）mm²也明显小于OC组（0.763 ± 0.015）mm²，差异有统计学意义（t = 83.174，P<0.001）。相对OC组，OC+DPSC共培养组的MMP-9、NFATc1及TRAP的mRNA相对表达量明显降低，均值分别为0.38 ± 0.17（t = 6.217，P = 0.003）、0.24 ± 0.12（t = 10.569，P = 0.003）和0.55 ± 0.13（t = 6.077，P = 0.026）。micro-CT扫描结果显示，DPSC注射组CEJ-ABC的平均距离为（0.215 ± 0.017）mm，明显小于0.9%氯化钠溶液组（0.311 ± 0.022）mm，差异有统计学意义（t= 10.921，P<0.001），组织学观察下DPSC组炎症反应较0.9%氯化钠溶液组轻，且破骨细胞更少。

DPSC可通过抑制牙周炎破骨细胞的形成从而促进牙槽骨再生，有望作为一种可局部注射的骨代谢双向调节生物制剂，治疗临床上包括牙周炎等因骨代谢失衡引起的炎症性骨吸收疾病。

To explore the effect of dental pulp stem cells (DPSC) on osteoclasts and the regeneration of the alveolar bone in periodontitis, and to preliminarily investigate the underlying machanism.

Monocytes were co-cultured with DPSC on osteoclastogenesis. TRAP staining were performed to observe the osteoclastogenesis of osteoclast group and DPSC co-culture group, and RT-PCR was applied to analyze the osteoclast-related genes, including NFATc1, MMP-9 and TRAP. Periodontitis models were established. Micro-CT scanning was performed to evaluate the distance from cementum-enamel junction to alveolar bone crest (CEI-ABC) of DPSC injection group and 0.9% sodium chloride solution injection group. HE and TRAP staining were also performed to compare the inflammatory response and osteoclast formation. The data were processed by the SPSS 20.0 software. T test and t′ test were used to analyze the difference between the groups.

It′s found in TRAP staining that co-culture with DPSC successfully inhibited osteoclast formation. The mean osteoclast number in DPSC co-culture group (4.2 ± 0.2) was significantly less than osteoclast group (6.8 ± 0.2) (t = 15.922, P<0.001) , and the mean cell size (0.046 ± 0.007) mm² was also less than osteoclast group (0.763 ± 0.015) mm² (t = 83.174, P<0.001) . Compared with those of osteoclast group, the expression of osteoclastogenesis-related genes including NFATc1, MMP-9 and TRAP of DPSC co-culture group were statistically lower, the value of which were 0.38 ± 0.17 (t = 6.217, P = 0.003) , 0.24 ± 0.12 (t = 10.569, P = 0.003) , 0.55 ± 0.13 (t = 6.077, P = 0.026) respectively. Micro-CT scanning showed that the CEI-ABC distance of DPSC group (0.215 ± 0.017) mm was lower than that of NS group (0.311 ± 0.022) mm (t = 10.921, P<0.001) . Histologic examination showed a less sever inflammatory response and a less osteoclast formation in DPSC group than those in NS group.

DPSC may promote the alveolar bone regeneration via inhibiting the osteoclast formation in chronic periodontitis. As a promising bi-directional biological agent for bone metabolism, DPSC may show good probability for the treatment of inflammatory bone resorption diseases including periodontitis in the future.