Mechanisms of Growth of a Pulmonary Capillary Network in Adult Lung

Abstract

The present study provides new insight into structural processes remodeling pulmonary capillaries in adult lung. The data highlight mechanisms underlying the expansion and increased density of capillary segments on return to air breathing (FiO₂ 0.21) after injury in high oxygen (FiO₂ 0.75). As segments expand and increase in number, endothelial cells extend their processes to bridge the lumen and support the walls of developing interluminal structures (ILSs); endothelial–epithelial surfaces infold as a single unit (sheet) into the lumen, increasing the length of each surface and subdividing segments by loop formation and by the formation of ILSs; segments further increase in number as lumen subdivision proceeds by intussusceptive microvascular growth (IMG).

• Angiogenesis
• capillary segment increase
• capillary sub-division
• endothelial cell bridging
• intussusceptive microvascular growth
• loop formation

Acknowledgements

We thank Rakesh Jain, Dai Fukumura, and Dan Duda (Department of Radiation Oncology, Harvard Medical School, and Steele Laboratory for Tumor Biology, Massachusetts General Hospital, Boston, MA) for providing the FVB-Tie2 and FVB-WT mice.