Antin P B, Taylor R G, Yatskievych T
Department of Animal Sciences, University of Arizona, Tucson 85721.
Dev Dyn. 1994 Jun;200(2):144-54. doi: 10.1002/aja.1002000206.
The establishment of precardiac mesoderm and the role of anterolateral endoderm and ectoderm in regulating heart muscle cell development have been studied in quail using explant cultures. Mesoderm from precardiac regions of stage 4(+)-6 embryos was explanted alone or in combination with adjacent endoderm or ectoderm, cultured for 12 to 72 hr in several types of culture media, and then assayed by morphological and immunocytochemical criteria for the presence of differentiated cardiac myocytes. Results show that mesoderm from heart forming regions is capable of differentiating into beating cardiac myocytes in a defined medium lacking potential signaling molecules by stage 4+, the earliest time at which we could isolate mesoderm from adjacent cell layers. Although an interaction with anterolateral endoderm from stage 4+ onward is therefore not required for the specification of precardiac mesoderm in quail, explants consisting of mesoderm plus endoderm show an enhanced rate of myocyte differentiation and a shortened delay between expression of myosin heavy chain and the onset of beating. Endoderm also plays a central role in early heart morphogenesis since beating heart tubes form only in explants that contain both mesoderm and endoderm. In contrast, ectoderm from stage 4(+)-5+ embryos does not support development of precardiac mesoderm. These results suggest that early heart muscle cell development involves an initial specification step that occurs prior to or during gastrulation and which leads to the appearance of myocardial precursor cells, and a subsequent differentiation step during which endoderm plays a central role in enhancing the rate of myocyte differentiation and the degree of heart tube morphogenesis.
利用外植体培养技术，在鹌鹑中研究了心脏前中胚层的建立以及前外侧内胚层和外胚层在调节心肌细胞发育中的作用。将4（+）-6期胚胎心脏前区的中胚层单独或与相邻的内胚层或外胚层联合进行外植，在几种类型的培养基中培养12至72小时，然后通过形态学和免疫细胞化学标准检测分化心肌细胞的存在。结果表明，在缺乏潜在信号分子的特定培养基中，心脏形成区域的中胚层在4+期就能够分化为跳动的心肌细胞，这是我们能够从相邻细胞层分离中胚层的最早时间。因此，虽然从4+期开始与前外侧内胚层的相互作用对于鹌鹑心脏前中胚层的特化不是必需的，但由中胚层加内胚层组成的外植体显示出心肌细胞分化率提高，肌球蛋白重链表达与跳动开始之间的延迟缩短。内胚层在早期心脏形态发生中也起着核心作用，因为只有在同时含有中胚层和内胚层的外植体中才能形成跳动的心脏管。相比之下，4（+）-5+期胚胎的外胚层不支持心脏前中胚层的发育。这些结果表明，早期心肌细胞发育涉及一个初始特化步骤，该步骤发生在原肠胚形成之前或期间，导致心肌前体细胞的出现，以及随后的分化步骤，在此期间内胚层在提高心肌细胞分化率和心脏管形态发生程度方面起着核心作用。
