Eralp Ismail, Lie-Venema Heleen, Bax Noortje A M, Wijffels Maurits C E F, Van Der Laarse Arnoud, Deruiter Marco C, Bogers Ad J J C, Van Den Akker Nynke M S, Gourdie Robert G, Schalij Martin J, Poelmann Robert E, Gittenberger-De Groot Adriana C
Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands.
Anat Rec A Discov Mol Cell Evol Biol. 2006 Dec;288(12):1272-80. doi: 10.1002/ar.a.20398.
During embryonic development, the proepicardial organ (PEO) grows out over the heart surface to form the epicardium. Following epithelial-mesenchymal transformation, epicardium-derived cells (EPDCs) migrate into the heart and contribute to the developing coronary arteries, to the valves, and to the myocardium. The peripheral Purkinje fiber network develops from differentiating cardiomyocytes in the ventricular myocardium. Intrigued by the close spatial relationship between the final destinations of migrating EPDCs and Purkinje fiber differentiation in the avian heart, that is, surrounding the coronary arteries and at subendocardial sites, we investigated whether inhibition of epicardial outgrowth would disturb cardiomyocyte differentiation into Purkinje fibers. To this end, epicardial development was inhibited mechanically with a membrane, or genetically, by suppressing epicardial epithelial-to-mesenchymal transformation with antisense retroviral vectors affecting Ets transcription factor levels (n=4, HH39-41). In both epicardial inhibition models, we evaluated Purkinje fiber development by EAP-300 immunohistochemistry and found that restraints on EPDC development resulted in morphologically aberrant differentiation of Purkinje fibers. Purkinje fiber hypoplasia was observed both periarterially and at subendocardial positions. Furthermore, the cells were morphologically abnormal and not aligned in orderly Purkinje fibers. We conclude that EPDCs are instrumental in Purkinje fiber differentiation, and we hypothesize that they cooperate directly with endothelial and endocardial cells in the development of the peripheral conduction system.
在胚胎发育过程中，前心外膜器官（PEO）在心脏表面生长并形成心外膜。经过上皮-间充质转化后，心外膜衍生细胞（EPDCs）迁移至心脏，对冠状动脉、瓣膜和心肌的发育起作用。外周浦肯野纤维网络由心室心肌中分化的心肌细胞发育而来。由于禽类心脏中迁移的EPDCs的最终目的地与浦肯野纤维分化之间存在紧密的空间关系，即围绕冠状动脉和心内膜下部位，我们研究了抑制心外膜生长是否会干扰心肌细胞向浦肯野纤维的分化。为此，通过用膜进行机械抑制，或通过用影响Ets转录因子水平的反义逆转录病毒载体抑制心外膜上皮-间充质转化来进行基因抑制（n = 4，HH39 - 41）。在两种心外膜抑制模型中，我们通过EAP - 300免疫组织化学评估浦肯野纤维的发育，发现对EPDC发育的限制导致浦肯野纤维形态异常分化。在动脉周围和心内膜下位置均观察到浦肯野纤维发育不全。此外，细胞形态异常，未排列成规则的浦肯野纤维。我们得出结论，EPDCs在浦肯野纤维分化中起重要作用，并且我们推测它们在周围传导系统的发育中直接与内皮细胞和心内膜细胞合作。
