Objective:
We examined whether the hematopoietic cells induce the coronary artery formation using genetically modified mouse models of hematopoietic ablation
in vivo
and
ex vivo
.
Methods:
As a model of for hematopoietic cell deficient animals, we used Runx1 (a transcription factor required for definitive hematopoiesis) knockout embryos and Vav1-cre; R26-DTA embryos, which ablates 2/3 of CD45+ hematopoietic cells. The coronary growth and the hematopoietic cells were evaluated in whole-mount, section and
ex vivo
explant culture.
Results:
The developing coronary endothelial cells form blood-island-like structure at around E12.5 in the subepicardial region. Interestingly, however, the histological analyses suggest that the first Ter119+ and CD45+ blood cells appear in the subendocardial area at E10.5, even before the formation of coronary channels. These initial hematopoietic cells in the heart are not likely derived from the epicardium, as the sorted epicardial cells yielded no hematopoietic cell in colony formation assay. These observations raised a question whether these heart-resident hematopoietic cells rather play an inductive role during coronary formation. To examine this possibility, we analyzed two hematopoietic ablation models. Both Runx1 knockout embryos and Vav1-cre; R26-DTA embryos revealed disorganized, hypoplastic microvasculature of coronary vessels on section and whole-mount stainings. Furthermore, coronary explant experiments showed that the mouse heart explants from Runx1 knockout embryos and Vav1-cre; R26-DTA embryos exhibited impaired coronary formation
ex vivo.
Conclusion:
Hematopoietic cells are not merely transported via coronary vessels, but substantially involved in the induction of the coronary vessels during cardiogenesis.
Human Ex vivo Wound Model and Whole-Mount Staining Approach to Accurately Evaluate Skin Repair