目的  探讨微RNA（miR）-21-5p通过NOD样受体热蛋白结构域相关蛋白3（NLRP3）/胱天蛋白酶1（CASP1）信号通路对脂多糖（LPS）诱导的大鼠急性牙髓炎（AP）的保护作用。 方法  将40只SD大鼠随机分为对照组（CON）、AP模型组（AP）、AP+miR-21-5p阴性对照组（AP+ NC）和AP+miR-21-5p 模拟剂组（AP+ agomir），每组10只。采用磨牙开髓后局部施加LPS（10 g/L）建立AP模型。AP+agomir组于模型构建后第1、2天局部注射miR-21-5p agomir（5 μmol/L）。模型构建后第3天处死大鼠，HE染色和Masson染色观察开髓组织病理学改变，荧光原位杂交（FISH）联合免疫荧光检测miR-21-5p表达；Real-time PCR检测miR-21-5p、肿瘤坏死因子α（TNF-α）、白细胞介素（IL）-6和IL-1β的mRNA水平，Western blotting检测NLRP3和CASP1蛋白表达；免疫组织化学检测IL-6、IL-1β和TNF-α阳性细胞表达， RNA测序分析差异表达基因。 结果  与CON组相比，AP组炎症细胞浸润显著增加，促炎因子TNF-α、IL-6、IL-1β表达升高，miR-21-5p表达下降。MiR-21-5p agomir可显著减轻炎症浸润，促进胶原纤维与修复性牙本质形成，并下调NLRP3、CASP1蛋白表达。RNA测序显示NLRP3炎性小体通路被显著抑制。 结论  MiR-21-5p通过抑制NLRP3/CASP1通路激活减轻LPS诱导的牙髓炎症。

Objective  To investigate the protective effect of microRNA-21-5p on lipopolysaccharide (LPS)-induced acute pulpitis (AP) in rats via the Nod-like receptor pyrin domain-containing (NLRP3)/cysteine aspartate 1 (CASP1) signaling pathway.  Methods  Forty SD rats were randomly divided into four groups, including control group (CON), AP model group (AP), AP+miR-21-5p negative control group (AP+ NC), and AP+miR-21-5p agomir group (AP+ agomir), n=10 per group. The AP model was established by opening the pulp chamber of molars and locally applying LPS (10 g/L). The AP+ agomir group received local injections of miR-21-5p agomir (5 μmol/ L) on day 1 and 2 after modeling. On the third day after model construction, rats were euthanized. Histopathological changes in the pulp were observed via HE staining and Masson staining. Fluorescence in situ hybridization (FISH) combined with immunofluorescence was used to detect miR-21-5p expression. Real-time PCR measured mRNA levels of miR-21-5p, tumor necrosis factor α (TNF-α), interleukin (IL)-6, and IL-1β. Western blotting assessed NLRP3 and CASP1 protein expression. Immunohistochemistry examined the expression of IL-6, IL-1β, and TNF-α-positive cells. RNA sequencing (RNA-seq) analyzed differentially expressed genes.   Results  Compared with the CON group, the AP group exhibited significantly increased inflammatory cell infiltration, elevated expression of pro-inflammatory factors (IL-6, IL-1β, and TNF-α), and decreased expression of miR-21-5p. Agomir targeting miR-21-5p significantly reduced inflammatory infiltration, promoted collagen fiber formation and reparative dentin formation, and downregulated the expression of NLRP3 and CASP1 proteins. RNA sequencing revealed that the NLRP3 inflammasome pathway was significantly inhibited.   Conclusion  MiR-21-5p alleviates LPS-induced dental pulp inflammation by inhibiting the activation of the NLRP3/CASP1 pathway.