Fig. 5

Fig. 5

Intussusceptive angiogenesis—the methodological challenge. a Scanning electron microscopy image of transluminar pillars. Early stage is characterized by tinny pillar (arrow), formed mainly by endothelial protrusions coming from the opposing EC. At later stages, the pillar (arrowhead) is increasing in girth and its core is invaded by perivascular cells, fibroblasts, and fibers (visible in the lower disrupted part of the pillar). Lumen of the vessel is marked with asterisks. Adapted from [647]. b Dynamic in vivo observation of the regenerating zebrafish fin vasculature demonstrated a newly formed pillar (rectangle). c Three-dimensional reconstruction based on serial semi-thin sections from the same area depicted in b, d transmission electron micrograph demonstrates the transluminal tissue pillars (rectangle in b, c) at ultrastructural level. Black asterisk indicates the core of the pillar, while arrowhead pointed to cell–cell contacts between the endothelial cells (EC). Er erythrocyte, Col collagen fibers. Adapted from [648]