To explore the impact of triggering receptor expressed on myeloid cells 2 (Trem2) on alveolar socket bone healing in mice with periodontitis after tooth extraction.

A murine periodontitis model was established using the silk ligature method, and changes in the expression of TREM2⁺ macrophages within the alveolar socket were detected by immunofluorescence staining. A periodontitis tooth-extraction model was established using Trem2 gene knockout (Trem2^-/-) mice, and alveolar socket bone healing was evaluated by Micro-CT, Masson staining, and tartrate-resistant acid phosphatase (TRAP) staining. Mouse bone marrow-derived macrophages (BMDMs) and bone marrow mesenchymal stromal cells (BMSCs) were cultured in vitro to establish an indirect co-culture system, and the osteogenic differentiation capacity of BMSCs was assessed by real-time quantitative polymerase chain reaction (RT-qPCR) and alkaline phosphatase (ALP) staining.

The number of TREM2⁺ macrophages within the alveolar socket increased after tooth extraction in mice with periodontitis. Compared with wild-type (WT) mice, Trem2^-/- mice exhibited reduced new bone formation, a decreased bone volume fraction (bone volume/tissue volume, BV/TV), and decreased new bone collagen deposition within the alveolar socket at 7 and 14 days after tooth extraction; the number of osteoclasts within the alveolar socket increased at 14 days after tooth extraction. In vitro experiments showed that, compared with the conditioned medium from the WT group, the conditioned medium from the Trem2^-/- group induced lower expression levels of Alp, Runx2, and Sp7 and weaker ALP activity in BMSCs.

In the microenvironment of periodontitis, macrophage Trem2 plays a crucial regulatory role in alveolar socket healing. In the in vitro indirect co-culture system with BMSCs, reduced Trem2 expression attenuates the ability of BMDMs to induce the osteogenic differentiation of BMSCs.

探究巨噬细胞髓样细胞触发受体2（triggering receptor expressed on myeloid cells 2，Trem2）对牙周炎小鼠拔牙后牙槽窝骨愈合的影响。

采用丝线结扎法构建牙周炎模型，通过免疫荧光染色法检测牙槽窝内TREM2⁺巨噬细胞的表达变化。采用Trem2基因敲除（Trem2^-/-）小鼠建立牙周炎拔牙模型，通过Micro-CT、Masson染色及抗酒石酸酸性磷酸酶（tartrate-resistant acid phosphatase，TRAP）染色评价牙槽窝骨愈合情况。体外培养小鼠骨髓来源巨噬细胞（bone marrow-derived macrophages，BMDMs）和骨髓间充质基质细胞（bone marrow mesenchymal stromal cells，BMSCs），并构建间接共培养体系，采用实时定量聚合酶链反应（real-time quantitative polymerase chain reaction，RT-qPCR）及碱性磷酸酶（alkaline phosphatase，ALP）染色检测BMSCs成骨分化能力。

牙周炎小鼠拔牙后牙槽窝内TREM2⁺巨噬细胞数量增加。与野生型（wild-type，WT）小鼠相比，Trem2^-/-小鼠拔牙后7 d和14 d牙槽窝内新生骨量减少，骨体积分数（bone volume/tissue volume，BV/TV）降低，新生骨胶原沉积减少；拔牙后14 d牙槽窝内破骨细胞数量增加。体外实验结果显示，与WT组条件培养液相比，Trem2^-/-组条件培养液诱导的BMSCs中Alp、Runx2及Sp7表达水平降低，ALP活性减弱。

在牙周炎微环境下，巨噬细胞Trem2在牙槽窝愈合过程中发挥重要调控作用，在BMSCs的体外间接培养体系中，Trem2表达降低会减弱BMDMs对BMSCs的成骨分化诱导能力。