The effect of absent blood flow on the zebrafish cerebral and trunk vasculature

The role of blood flow is complex and context-dependent. In this study, we quantify the effect of the lack of blood flow on vascular development and compare its impact in two vascular beds, namely the cerebral and trunk vasculature, using zebrafish as preclinical model. We performed this by analysing vascular topology, endothelial cell number, apoptosis, and inflammatory response in animals with normal blood flow or absent blood flow. We find that absent blood flow reduced vascular area and endothelial cell number significantly in both examined vascular beds, but the effect is more severe in the cerebral vasculature. Similarly, while stereotypic vascular patterning in the trunk is maintained, intra-cerebral vessels show altered patterning. Absent blood flow lead to an increase in non-EC-specific apoptosis without increasing tissue inflammation, as quantified by cerebral immune cell numbers and nitric oxide. In conclusion, blood flow is essential for cellular survival in both the trunk and cerebral vasculature, but particularly intra-cerebral vessels are affected by the lack of blood flow, suggesting that responses to blood flow differ between these two vascular beds. Key points We here use zebrafish as a model to quantitatively assess the impact of the lack of blood flow in development and compare its impact in two vascular beds, namely the cerebral to trunk vasculature. In both vascular beds, vascular growth and endothelial cell number are reduced by lack of blood flow, with increasing effect size from 2-5 days post fertilisation. Examination of vascular patterning shows that while stereotypic patterning in the trunk is preserved, the intra-cerebral vasculature patterning is altered. We found non-EC-specific cell death to be increased in both vascular beds, with a larger effect size in the brain, but that this cell death occurs without triggering tissue inflammation.