BS19 Effect of chronic low-level carbon monoxide exposure on early cardiac development in an avian model

Durrans, Joshua, Herigstad, Mari, Stafford, Prachi, Clarke Sheffield, Simon and Ridge, Liam (2025) BS19 Effect of chronic low-level carbon monoxide exposure on early cardiac development in an avian model. In: Heart, A253-A254. Presented at British Cardiovascular Society Annual Conference, 2 June - 4 June 2025, Manchester Central Convention Complex, Manchester, UK.

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Abstract

Introduction Carbon monoxide (CO) is an air pollutant that we are exposed to daily, however, little is known about the low-level effects (<10ppm). Recent epidemiological data has shown links between ambient CO-exposure and congenital heart defects, but further work is needed to confirm these findings. The avian model will be used to study the in-vivo effects of CO exposure due to the morphological and highly conserved genetic similarities in cardiac development with the human heart. This will allow data to be extrapolated, which is important due to the unethical nature of exposing a human embryo to CO. We hypothesise that at low levels, CO could affect heart morphology through several mechanisms that may harm cardiovascular development. Methods We first separated fertilised chicken eggs (Gallus gallus domesticus) into airtight incubation boxes. Half were injected with CO, and the other half were kept as air controls. The boxes were opened three times a day to turn the eggs to prevent the embryo membranes from sticking to the inside shell causing death. On day 9 of development, the embryo was sacrificed and the heart excised. Samples were fixed and processed for FFPE sectioning in coronal and transversal orientation. We first stained sections with H&E to assess the thickness of the ventricular walls, after which, we moved on to immunofluorescent staining to investigate cardiac hypertrophy, hyperplasia and apoptosis using WGA-FITC to stain for cell membranes, phosphohistone-H3 for proliferating cells and a TUNEL kit for apoptotic cells. Results We found that exposure to levels of 10ppm resulted in significant thickening of the left-ventricular walls of the day 9 chick heart, however, no change was noted in the right ventricular walls. We moved on to investigate cardiac hyperplasia and apoptosis in the ventricular walls, our findings suggested a significant increase in proliferation rate within the compact myocardium of the left ventricle, but no change in proliferation of the right ventricular myocardium. We also found no effect on the rate of apoptosis post-CO exposure. Conclusion In conclusion, we have shown that even at low-levels, CO exposure results in myocardial hypertrophy and hyperplasia of the left ventricle. CO has also been shown to increase the nuclei size of cardiomyocytes. Further work is needed to elucidate specific cellular and sub-cellular mechanisms that cause the observed changes in phenotype. Future experiments will use microcomputed tomography to collect high-resolution three-dimensional reconstructions of the embryonic heart for detailed morphological and volumetric analysis. We also suggest using human cell lines to confirm these effects. This novel work has the impact to uncover the low-level harms of CO to better understand its pathologies and inform decisions made on public health policy.