Vascular permeability to plasma, plasma proteins, and cells: an update

The blood vasculature supplies tissues with nutrients, clears waste products, and carries and directs leukocytes to inflammatory sites. To accomplish these functions, microvessels regulate the extravasation of small molecules, plasma proteins and inflammatory cells. The mechanisms responsible for these events have been the subject of intense investigation and, often, dispute.

Recent progress has contributed to a better understanding of the mechanisms by which microvessels of different types and in different vascular beds regulate the passage of small and large molecules and cells. Roles are shown for the glycocalyx, caveolae, perictyes, sphingosine-1-phosphate, and newly discovered signaling pathways.

Vascular permeability is important for maintaining homeostasis and is greatly increased in acute and chronic inflammation, wound healing, and growing tumors. New work has contributed importantly to the mechanisms responsible for regulating permeability.