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目的：观察胚胎早期间充质细胞增殖、分化的改变，明确下颌骨在胚胎早期由细胞凝聚到定向分化成成骨细胞而发育形成的过程。方法：用免疫组化及ＴＵＮＥＬ染色等方法，检测了胚龄１３～１９ｄ及出生１ｄ的小鼠下颌骨中未分化间充质细胞增殖、细胞程序性死亡（ＰＣＤ）及表型转化的生物学改变。结果：胚龄１３～１５ｄ，间充质细胞开始凝聚形成下颌骨始基并迅速增殖。胚龄１６～１９ｄ，凝聚区细胞明显向成骨细胞表型转化并开始成骨。麦克尔软骨消失。结论：下颌骨的发育始于胚胎间充质细胞的局部凝聚，大部分细胞经历了快速增殖后逐渐分化成熟，少量细胞出现ＰＣＤ以清除病变或非必需细胞并与麦克尔软骨的发生及退化有密切关系
OBJECTIVE: To observe the changes of proliferation and differentiation of early mesenchymal cells in embryos, and to clarify the process of the formation and development of the mandible from the cell agglutination to the directional differentiation into osteoblasts in the early embryo. Methods: Immunohistochemistry and TUNEL staining were used to detect the proliferation of undifferentiated mesenchymal cells, programmed cell death (PCD) and phenotypic transformation in the mandible from embryonic day 13 to day 19 and day 1 of birth change. Results: From embryonic age 13 to 15 days, mesenchymal cells began to aggregate to form the primordium of mandible and rapidly proliferated. The embryo age was 16-19 days, and the cells in the cohesion area obviously transformed into osteoblast phenotype and began to form osteogenesis. Mecker cartilage disappears. Conclusion: The development of the mandible begins with local agglutination of embryonic mesenchymal cells. Most of the cells gradually differentiate and mature after experiencing rapid proliferation. A small number of cells show PCD to clear the pathological or non-essential cells and develop and degrade the cartilage close relationship