Early heart development: Dynamics of endocardial cell sorting suggests a common origin with cardiomyocytes

Abstract

The myocardial and endocardial cell sorting out processes take place primarily between 19 and 29 hr of development in the avian embryo. This occurs in an apparent rostra1 to caudal wave through the heart forming region. During heart development considerable uncertainty exists regarding the processes that regulate cell commitments, progressive aggregation, and sorting out of the different precardiac cell populations. The question addressed in this report is whether endocardial and myocardial cells have a common origin or do the endocardial cells arise from a distinct population of cells from within the precardiac mesoderm. These cells then migrate to become localized between the developing myocardium above and the endoderm below. The distribution of preendocardial cells and premyocardial cells has been followed immunohistochemically in quail heart-forming region mesoderm explants from embryos approximately 18 hr in development and incubated for a 24-hr period. Differentiating myocardiocytes were immunostained with anti-N-cadherin and endocardiocytes with QH-1, a monoclonal antibody that recognizes an antigenic determinant on quail endothelial cells. Sparsely localized QH-1 labeled endothelial cells are localized in the stage 5 heart-forming region. These cells are often arranged in a columnar fashion in the mesoderm explants 6 hr after explantation. By 15-22 hr large patches of QH-1 expressing cells are interspersed with the N-cadherin expressing myocardiocytes. A subpopulation of cells express both N-cadherin and QH-1 antigen suggesting that endocardial and myocardial cells may arise from a common precursor population and that N-cadherin regulation may be a mechanism underlying specific cell sorting of these two cell populations during heart development. o 1993 WiIey-Liss, Inc.

Anterior endoderm is a specific effector of terminal cardiac myocyte differentiation of cells from the embryonic heart forming region

“…Previous studies of cardiac myocyte development in vitro utilized cells explanted into medium that was supplemented with serum or embryo extract (DeHaan, 1964;Gonzalez-Sanchez and Bader, 1990;Linask and Lash, 1993). Because such supplements are enriched in a variety of growth factors, indications that cardiogenesis can occur in the absence of interacting cells must be cautiously interpreted.…”

Cardiac cell proliferation assessed by EdU, a novel analysis of cardiac regeneration

“…At the same time, non-muscle cells play important roles in the heart. During embryonic cardiac development, endothelial cells share the same cardiac mesodermal precursors with cardiomyocytes (Linask and Lash 1993). Interaction between endothelial cells and cardiomyocytes in the heart regulates normal heart functions (Narmoneva et al 2004).…”

Cardiac endothelium: More than just a barrier

“…(13) Interestingly, in a study on quail embryos, it was found that EECs and cardiomyocytes initially develop from the same cardiac mesodermal region, although they eventually separate from each other. (14) In fact, in early embryonic development, the EECs are the only endothelial cell subtype present in the primitive spongious heart tube, where they exist alongside the cardiomyocytes, in which, at around this time, the very fi rst contractions begin to appear. (13) The discovery that embryonic EECs release neuregulin, a member of the epidermal growth factor family, supported speculation of an obligatory role for EECs in cardiomyocyte growth and development, especially since it was also (6) shown that the embryonic cardiomyocytes express the neuregulin receptors, ErbB2 and ErbB4.…”