Hypoxia differentially affects coronary vessel formation during heart development.

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Molecular Cardiology

Background:

• The coronary vessel system is a complex network crucial for heart function.
• Hypoxia (low oxygen) is a known driver of angiogenesis (new blood vessel formation).
• The precise mechanisms of hypoxia-induced cardiac angiogenesis, particularly involving Vascular Endothelial Growth Factor A (VEGFA), remain unclear.

Purpose of the Study:

• To investigate the specific mechanisms by which hypoxia influences coronary vessel growth and development in the heart.
• To elucidate the role of VEGFA and associated regulatory pathways in hypoxia-driven cardiac angiogenesis.

Main Methods:

• A genetic model was employed to stabilize Hypoxia-Inducible Factor alpha (HIFα), mimicking myocardial hypoxia.
• Single-cell RNA sequencing and enhancer:reporter transgenes were used to analyze changes in coronary endothelial cells (ECs).
• Investigated activity in different coronary vessel beds and regulatory pathways, including VEGFA-MEF2.

Main Results:

• Mimicking hypoxia increased angiogenic gene expression and expanded the VEGFA-MEF2 pathway activity.
• Evidence pointed towards increased angiogenic sprouting originating from endocardial cells.
• Sprouting from the sinus venosus (SV)-derived plexus showed minimal change; initial arterial EC differentiation was unaffected, but mature arterial formation was delayed.

Conclusions:

• Hypoxia directly and specifically promotes endocardial coronary vessel sprouting.
• Hypoxia and VEGFA play a role in guiding the coalescence of coronary arteries.
• Findings highlight the distinct contributions of different cell sources to cardiac angiogenesis under hypoxic conditions.