Myocardial differentiation is dependent upon endocardial signaling during early cardiogenesis in vitro

Abstract

The endocardium interacts with the myocardium to promote proliferation and morphogenesis during the later stages of heart development. However, the role of the endocardium in early cardiac ontogeny remains under-explored. Given the shared origin, subsequent juxtaposition, and essential cell-cell interactions of endocardial and myocardial cells throughout heart development, we hypothesized that paracrine signaling from the endocardium to the myocardium is crucial for initiating early differentiation of myocardial cells. To test this, we generated an in vitro, endocardial-specific ablation model using the diphtheria toxin receptor under the regulatory elements of the Nfatc1 genomic locus (NFATc1-DTR). Early treatment of NFATc1-DTR mouse embryoid bodies with diphtheria toxin efficiently ablated endocardial cells, which significantly attenuated the percentage of beating EBs in culture and expression of early and late myocardial differentiation markers. The addition of Bmp2 during endocardial ablation partially rescued myocyte differentiation, maturation and function. Therefore, we conclude that early stages of myocardial differentiation rely on endocardial paracrine signaling mediated in part by Bmp2. Our findings provide novel insight into early endocardial-myocardial interactions that can be explored to promote early myocardial development and growth.

Tie1 regulates zebrafish cardiac morphogenesis through Tolloid-like 1 expression

“…The tie1 mutant allele carries a 7 bp deletion in exon 14. Genotyping was performed by High-Resolution Melt Analysis (HRMA) (Samarut et al, 2016) using an Eco Real-Time PCR System (Illumina). HRMA primers were designed using ApE (forward primer 5 0 -TATTCCCACCACTCAGCAAG -3 0 and reverse primer 5 0 -ATGGTCA-CACAAGTCACAGC -3 0 ) with a 96 bp amplicon size.…”

Endocardial-Myocardial Interactions During Early Cardiac Differentiation and Trabeculation

“…Yet the paucity of available models to study myocardial differentiation without contributions from an endocardial population has made it difficult to further delineate the endocardial-myocardial signaling. Saint-Jean et al ( 45 ) recently developed a novel in vitro mouse ESC system to determine how myocardial differentiation is dependent on the endocardium, focusing on the initial stages of cardiogenesis. Using regulatory elements of the endocardial-specific marker, Nfatc1, they created a mouse stem cell line that expresses the diphtheria toxin receptor (Nfatc1-DTR) only within differentiated endocardial cells.…”

“…(F) Coronal sections of E8.25 NFATc1-nuc-LacZ embryo revealing blue β-gal expression specifically and exclusively in the endocardium. (G) Whole-mount immunofluorescence of an NFATc1-mCherry (BAC) E9.5 embryo confirms endocardium-specific mCherry expression [adapted from Misfeldt et al ( 40 ) and Saint-Jean et al ( 45 )].…”

Hedgehog Morphogens Act as Growth Factors Critical to Pre- and Postnatal Cardiac Development and Maturation: How Primary Cilia Mediate Their Signal Transduction

“…Primary cilia have vital roles in heart development, including allowing different areas of the embryonic heart to communicate and coordinate appropriately. It has been established that the signaling interactions between the endocardium (and the myocardium in later development) contribute to the proper development of the heart valves and the trabeculation of the ventricles [ 88 ]. Endocardial cells are defined as endothelial cells that are specifically localized within all four chamber walls of the heart [ 89 ].…”