Immunoultrastructural expression of ICAM-1 and PECAM-1 occurs prior to structural maturity of the murine blood-brain barrier.

This study investigated the time of expression of two endothelial cell adhesion molecules, ICAM-1/CD54 and PECAM-1/CD31 in the developing postpartum mouse blood-brain barrier (BBB). Immunoultrastructural studies demonstrated that both adhesion molecules are initially expressed primarily on the luminal endothelial cell surfaces at birth or shortly thereafter, they increase in an intensity at approximately 1 week postpartum and then decrease to a weak labeling of the luminal endothelial cell surfaces at 2 weeks after birth. In the adult animals, little or no adhesion molecule labeling was expressed on blood vessels. Our results present immunocytochemical evidence that upregulation of ICAM-1 and PECAM-1 occurs prior to structural maturity of the BBB. Moreover, these data support a notion that these adhesion molecules play an important role for angiogenesis in the developing murine BBB.