目的·观察Th17细胞特异性敲除Stat3基因对牙周炎小鼠焦虑抑郁样行为的影响。方法·通过Cre/LoxP系统繁育Th17细胞特异性敲除Stat3基因小鼠（Stat3^fl/fl；Il17a-CreERT2，即Stat3^△Il17a ）及野生型小鼠（Stat3^fl/fl，WT），腹腔注射他莫昔芬诱导基因敲除，通过磁珠分选法提取小鼠CD4⁺T细胞并诱导其Th17细胞分化，采用反转录聚合酶链反应及蛋白免疫印迹法验证基因敲除效率。实验分为4组，分别为野生型-对照组（WT-C）、基因敲除-对照组（Stat3^△Il17a -C）、野生型-牙周炎组（WT-P）和基因敲除-牙周炎组（Stat3^△Il17a -P），其中WT-P组和Stat3^△Il17a -P组采用龈沟注射牙龈卟啉单胞菌脂多糖（Porphyromonas gingivalis-lipopolysaccharide，P. gingivalis-LPS）建立小鼠实验性牙周炎模型。4周后通过旷场实验、高架零迷宫实验和强迫游泳实验观察小鼠焦虑抑郁样行为；显微计算机断层成像观察小鼠牙槽骨吸收情况；苏木精-伊红染色观察海马神经元损伤情况，并采用酶联免疫吸附法检测小鼠脑组织中脑源性神经营养因子（brain-derived neurotrophic factor，BDNF）表达情况。结果·Stat3^△Il17a 小鼠Th17细胞Stat3基因与蛋白表达均较WT小鼠显著下降（均P<0.05）。WT-P组和Stat3^△Il17a -P组成功建立小鼠实验性牙周炎模型，且Stat3^△Il17a -P组小鼠牙槽骨破坏程度较WT-P组轻。WT-P组小鼠与WT-C组小鼠比较，在旷场实验中进入中心区时间减少，在高架零迷宫实验中进入开放区时间减少，在强迫游泳实验中不动时间增加（均P<0.05），同时伴海马神经元损伤及BDNF表达水平显著下降（P<0.05）。Stat3^△Il17a -P组小鼠中异常行为学表现及海马神经元损伤程度，与WT-P组比较均有所减轻（均P<0.05），且Stat3^△Il17a -P组海马组织BDNF表达水平较WT-P组显著增加（P<0.05）。结论·牙周炎可导致小鼠产生焦虑抑郁样行为及神经元损伤，而Th17细胞特异性敲除Stat3基因可以显著减轻小鼠焦虑抑郁样行为和神经元病理改变；Stat3介导的Th17细胞免疫反应可能在牙周炎与焦虑、抑郁症状的关系中发挥重要的作用。

Objective ·To investigate the effect of Th17 cell-specific Stat3 knockout on anxiety- and depressive-like behaviors. Methods ·Mice with specific Stat3 knockout in Th17 cells (Stat3^fl/fl; Il17a-CreERT2), named Stat3^△Il17a , and wild-type mice (Stat3^fl/fl, WT) were generated through the Cre/LoxP system, and Stat3 knockout was induced by intraperitoneal injection of tamoxifen. CD4⁺T cells were isolated using magnetic-activated cell sorting and induced to differentiate into Th17 cells. Reverse transcription polymerase chain reaction and Western blotting were used to verify Stat3 knockout efficiency. Mice were assigned into 4 groups: WT-C group, Stat3^△Il17a -C group, WT-P group, and Stat3^△Il17a -P group. The periodontitis model was established in the WT-P group and the Stat3^△Il17a -P group by injection of Porphyromonas gingivalis-lipopolysaccharide (P. gingivalis-LPS) into the gingival sulcus. Behavioral tests, including the open field test, elevated zero maze, and forced swimming test, were conducted to evaluate changes in anxiety- and depressive-like behaviors. Micro-computed tomography was used to observe destruction of alveolar bone. Neuronal injury was observed by H-E staining, and the level of brain-derived neurotrophic factor (BDNF) was detected by enzyme-linked immunosorbent assay. Results ·mRNA expression and protein levels of Stat3 in Stat3^△Il17a mice were inhibited compared to WT mice (P<0.05). Experimental periodontitis model was successfully established in the WT-P group and the Stat3^△Il17a -P group. The degree of alveolar bone destruction was reduced in the Stat3^△Il17a -P group compared to the WT-P group. In the WT-P group, decreased residence time in the central area and in the open area was observed in the open field test and elevated zero maze respectively, and increased immortal time was recorded in the forced swimming test (P<0.05). Moreover, neuronal injury was detected and significantly decreased expression levels of BDNF in the brain were measured in the WT-P group compared with the WT-C group (P<0.05). The degree of abnormal behaviors and neuronal injury was reduced in the Stat3^△Il17a -P group compared to the WT-P group (P<0.05). Moreover, the level of BDNF in the Stat3^△Il17a -P was higher than that in the WT-P group (P<0.05). Conclusion ·Periodontitis may contribute to anxiety- and depressive-like behaviors and neuronal damage in mice, while Th17-specific conditional knockout of Stat3 could significantly alleviate pathological behaviors and neuronal damage. Stat3-mediated-Th17 cell immune responses may play a crucial role in the correlation between periodontitis and anxiety and depression.