Wildfire Ash Disrupts Heart Development in Chick Embryos

Wildfires burn plants and buildings, releasing smoke, ash, and harmful chemicals into the air. Recent wildfires in both California (Eaton and Palisade fires) and Hawaii (Maui fire) have caused major loss of life and property and economic damage. A recent study has highlighted a direct link between exposure to wildfire smoke during early pregnancy and a higher risk of babies being born with heart defects. The biological reasons for this link have not been determined. This study examined how wildfire ash collected in California from burned structures affects developing chicken heart in effort to model the role wildfires play in causing congenital heart defects in humans. The endothelial-to-mesenchymal transition (EMT) is a central cellular process involved in heart valve and development, which is critical for proper heart development. Abnormal atrioventricular (AV) canal EMT is an established cause of congenital heart defects. In this study, the collagen gel invasion assay, a well-established model of EMT, was used. Chicken AV canal explants at stage 16 were placed on a collagen gel to investigate the effects of wildfire ash in vitro. AV canal explants were grown on collagen gels and exposed to wildfire ash at different concentrations. Treatment time was kept as acute (12-36 hr) or prolonged (60 hr) exposure to wildfire ash. The data showed that wildfire ash inhibits AV canal EMT in a dose-dependent manner, impairing endothelial cell transformation into mesenchymal cell, reducing mesenchymal cell invasion, and ultimately inducing cell death at higher concentrations and prolonged exposure.