Coronary arteries play a crucial role in providing the human heart with oxygen-rich blood. A recent study conducted by a multi-institutional team of researchers aimed to understand the evolutionary development of these vital blood vessels in various species. By comparing the hearts of mammals, birds, reptiles, fish, and frogs, the researchers found evidence suggesting that the structure of our hearts evolved in a stepwise process from fish to amphibians, reptiles, and eventually mammals.
As animals transitioned from living in water to living on land, the blood vessels of their hearts underwent significant remodeling to enable survival without gills. Unraveling the ancestral origins of our cardiovascular system could help identify the basis for certain genetic defects. Furthermore, studying the cardiovascular systems of different animals expands our knowledge of heart diseases and potential treatments.
Congenital heart disease (CHD) is the most common birth defect globally, encompassing a range of issues, including anomalous coronary arteries. These malformed arteries can lead to sudden and dangerous complications due to the inadequate supply of oxygenated blood to the heart. However, not all species face this problem. Some animals, such as fish and amphibians, do not possess or require coronary arteries. This raises the question of why humans have them and where they originated from.
To address these questions, researchers in Japan compared the development of blood vessels in the hearts of mice, Japanese quails, newts, zebrafish, sharks, and frogs. The team employed various techniques, including MRI, micro-CT scans, and 3D reconstruction, to visualize and analyze the differences in vascular system development between amniotes (mammals, birds, and reptiles) and non-amniotes (fish, sharks, and amphibians) from embryos to adults.
The findings revealed that in fish, sharks, and amphibians, a long vascular system extending from the gills supplies blood to the heart. Conversely, in mammals and birds, this ancestral vascular system exists only during the embryo stage and later transforms into adult coronary arteries that wrap around the heart. This evolutionary change appears connected to the vertebrate transition from water to land, which led to the loss of gills.
Amphibians, sitting between fish and mammals on the evolutionary tree, offer insight into the transition from one type of heart to another. The researchers observed that the transient blood vessels found in mice embryos closely resemble the ancestral vascular system seen in amphibians. These vessels act as essential starting points for the formation of new coronary arteries in mice.
Overall, this study suggests that the structure of the human heart originated from a common amniote ancestor. The transition from water-dwelling to land-dwelling animals resulted in significant remodeling of ancestral blood vessels to form the coronary arteries found in humans today.
– Mizukami et al. (2023), eLife