In the past, the heart muscle was thought to originate from a single source of myocardial progenitor cells. More recently, however, an additional source of myocardial progenitors has been revealed to be the second heart field, and chicken embryos were important for establishing this concept. However, there have been few studies in chicken on how this field contributes to heart muscles in vitro. We have developed an ex vivo experimental system from chicken embryos between stages HH17-20 to investigate how mesodermal progenitors in the second branchial arch (BA2) differentiate into cardiac muscles. Using this method, we presented evidence that the progenitor cells within the BA2 arch differentiated into beating cardiomyocytes in vitro. The beating explant cells were positive for cardiac actin, Nkx2.5, and ventricular myosin heavy chain. In addition, we performed a time course for the expression of second heart field markers (Isl1 and Nkx2.5) in the BA2 from stage HH16 to stage HH21 using in situ hybridization. Accordingly, using EGFP-based cell labeling techniques and quail-chicken cell injection, we demonstrated that mesodermal cells from the BA2 contributed to the outflow tract and ventricular myocardium in vivo. Thus, our findings highlight the cardiogenic potential of chicken BA2 mesodermal cells in vitro and in vivo.

中文翻译：

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鸡第二鳃弓祖细胞在体外和体内有助于心脏肌肉组织

过去，人们认为心肌起源于单一来源的心肌祖细胞。然而，最近发现心肌祖细胞的另一个来源是第二心脏区域，而鸡胚胎对于建立这一概念很重要。然而，关于该领域如何在体外对心肌做出贡献的鸡研究很少。我们已经从 HH17-20 阶段之间的鸡胚胎开发了一种离体实验系统，以研究第二鳃弓 (BA2) 中的中胚层祖细胞如何分化为心肌。使用这种方法，我们提供了证据，证明 BA2 弓内的祖细胞在体外分化为跳动的心肌细胞。跳动的外植体细胞对心脏肌动蛋白、Nkx2.5 和心室肌球蛋白重链呈阳性。此外，我们使用原位杂交对从 HH16 阶段到 HH21 阶段的 BA2 中第二个心脏场标记（Isl1 和 Nkx2.5）的表达进行了时间过程。因此，使用基于 EGFP 的细胞标记技术和鹌鹑鸡细胞注射，我们证明了来自 BA2 的中胚层细胞有助于体内流出道和心室心肌。因此，我们的研究结果突出了鸡 BA2 中胚层细胞在体外和体内的心源性潜力。