Fig. 3: Heterogeneity of vascular permeability mechanism.
From: Machine-learning-assisted single-vessel analysis of nanoparticle permeability in tumour vasculatures
a, Zombie model with HT29 and 3LL demonstrates active or passive pathways for FTn penetration. Left: representative confocal images for vascular penetration in control and Zombie mice. Scale bar, 50 μm. Right: violin plot analysis of VP distribution using the nano-ISML approach. b, TEM images of active capture mechanisms of endothelial cells. Representative images of the entire vessel (left; scale bar, 1 μm) and enlarged images (right; scale bar, 100 nm) of three typical capture mechanisms (that is, pinocytosis, phagocytosis and endocytosis). L and R represent lumen of endothelial cell and red blood cell, respectively. Black triangles indicate the FTn-IO in the enlarged images. c, Quantitative analysis of the contribution of three capture mechanisms for the active pathway by counting FTn-IO numbers observed in tumour blood vessels. Each dot represents single vessel, and total 32 vessels were analysed. d, Single-vessel analysis of 3LL tumours with or without the pinocytosis inhibitor EIPA (3LL-EIPA). Representation confocal images of tissue sections from 3LL and 3LL-EIPA are shown (left). Blue, nucleus; green, vessel; magenta, FTn. Scale bar, 50 μm. Violin plot analysis of the distribution of VP for each vessel is listed (right). e, Quantitative analysis of the percentage of HP, MP and LP vessels, obtained from d. f, Typical features of formed vesicles (black star) in active vessels and inactive vessels. Representative TEM images of formed large vesicles for active vessel (top left) and small vesicles for inactive vessel (bottom left). Scale bar, 100 nm. Quantitative analysis of the distribution of vesicle diameters in active vessels (top right, n = 4,850) and inactive vessels (bottom right, n = 1,560). g, Diagram illustrating the dominant vascular penetration mechanism in HP tumours and LP tumours. HP tumours are primarily dependent on the passive extravasation mechanism via interendothelial gap and VVO pathways, whereas active transendothelial transport mechanism following pinocytosis is the dominant manner for LP tumours. Data are presented as mean ± s.e.m.
