Conclusions
Our in vivo fate-mapping studies demonstrated that the developing endocardium, but not the vascular endothelial cells, gives rise to intramyocardial adipocytes in the adult heart.
Objective
To trace the developmental origin of intramyocardial adipocytes.
Results
In this study, we identified that the majority of intramyocardial adipocytes were restricted to myocardial regions in close proximity to the endocardium. Using a genetic lineage tracing model of endocardial cells, we found that Nfatc1(+) endocardial cells contributed to a substantial number of intramyocardial adipocytes. Despite the capability of the endocardium to generate coronary vascular endothelial cells surrounding the intramyocardial adipocytes, results from our lineage tracing analyses showed that intramyocardial adipocytes were not derived from coronary vessels. Nevertheless, the endocardium of the postnatal heart did not contribute to intramyocardial adipocytes during homeostasis or after myocardial infarction. Conclusions: Our in vivo fate-mapping studies demonstrated that the developing endocardium, but not the vascular endothelial cells, gives rise to intramyocardial adipocytes in the adult heart.