Elucidating mechanics of vascular regression in Botryllus schlosseri using image analysis

Epithelial tubules form critical structures in various body tissues; however, due to experimental inaccessibility, their architecture and dynamics are not well understood. We examined epithelial tube remodeling in vivo using a novel model system: Botryllus schlosseri vasculature.
In Botryllus, blood vessel retraction can be triggered through disrupting (i) collagen crosslinking in the basement membrane using β-aminopropionitrile (BAPN); or (ii) integrin pathway through inhibition of focal adhesion kinase (FAK)(Rodriguez D et al. 2017). We performed stereographic projections of 3-dimensional confocal scans to ‘unwrap’ the blood vessels to enable quantitative analysis of morphology. In normal vessels, the cells are axially elongated with circumferentially aligned actin bundles. While we found no differences in morphology between normal and BAPN treated vessels, FAK-inhibited vessels have significantly smaller cells with circumferential cell orientation. Our results demonstrate the feasibility of Botryllus for imaging-based studies of the mechanics of epithelial tube remodeling; in addition, they suggest a critical role of integrin in the maintenance of epithelial morphology.