目的 探讨转录因子Tbx3在小鼠胚胎第二生心区（SHF）的时空表达模式，为其对SHF的调节作用提供形态学依据。 方法 40只胚龄9～15 d小鼠胚胎心脏连续石蜡切片，用抗胰岛素基因增强子结合蛋白1（ISL-1）抗体、抗心肌肌球蛋白重链（MHC）抗体、抗心肌肌球蛋白轻链Ⅱa（MLC2a）抗体、小鼠抗增殖细胞核抗体（PCNA）、抗Tbx3抗体进行免疫组织化学和免疫荧光双标染色。 结果 胚龄9 d，咽腹侧内胚层增厚，且表达Tbx3与SHF标记物ISL-1。胚龄10～12 d，咽腹侧间充质出现ISL-1阳性细胞并逐渐增多，部分细胞共表达Tbx3。动脉囊壁、心包腔背侧壁以及流出道远端壁也可见ISL-1表达，Tbx3在这些部位均呈阴性。心背侧间充质突（DMP）内可见ISL-1、Tbx3散在表达。胚龄13～15 d，DMP逐渐心肌化，同时可见Tbx3阳性细胞分布。 结论 Tbx3在SHF的表达集中在咽腹侧间充质，可能参与调节SHF前体细胞的存在与增殖；但在后第二生心区（pSHF）的作用与在动脉端的SHF可能不同。

Objective To investigate the expression pattern of Tbx3 in the mouse embryonic second heart field (SHF) to provide morphological basis for the study of the regulation mechanism in SHF. Methods Serial sections of 40 mouse embryonic hearts aged from embryonic day（ED）9 to ED15 were stained by immunohistochemistry or double-label immunofluorescence with antibodies against islet-1 (ISL-1), myosin heavy chain (MHC), myosin light chain 2 a (MLC2a), proliferating cell nuclear antigen (PCNA) and T-box transcription factor 3 (Tbx3). Results Immunohistochemical positive staining for Tbx3 and SHF marker ISL-1 was distributed in pharyngeal ventral endoderm of ED9 mouse. During ED10 to ED12, immunohistochemical positive staining for ISL-1 was presented in pharyngeal ventral mesenchymal and staining intensity was increased gradually. Some ISL-1 positive mesenchymal cells were co-expressed with Tbx3. ISL-1 was also shown in the aortic sac wall, pericardial dorsal wall and the distal pole of the outflow tract, where Tbx3 was negative. However, the dorsal mesenchymal protrusion (DMP) contained ISL-1 or Tbx3 positive cells. During ED13 to ED15, DMP was myocardialized and sporadic Tbx3 positive cells were seen in DMP. Conclusion Tbx3 expression is mainly concentrated in pharyngeal ventral mesenchyme, which suggests that Tbx3 may contribute to the survive and proliferation of SHF progenitor cells. However, its function is different in posterior second heart field（pSHF）and in SHF of arterial pole of embryonic heart.