Aquaporin-1 expression in the chick embryo chorioallantoic membrane.

The chick embryo chorioallantoic membrane (CAM) is commonly used in vivo to study both angiogenesis and anti-angiogenesis. Rapid membrane water transport is mediated by a family of molecular water channels, called aquaporins (AQPs), which have been identified in the epithelial and endothelial cells of higher vertebrates. AQP1, expressed in adsorptive and secretory epithelia, is also expressed in endothelial cells of capillaries and arteries. Its mRNA has been found in vascular smooth muscle cells (VSMCs) of arteries and capillaries, as well as in a subset of VSMCs of human atherosclerotic plaques. This study investigated the developmental expression of AQP1 in the chick CAM by Western blot and immunohistochemistry. Western blot results show that a major nonglycosylated band was observed with electrophoretic mobility of approximately 28 kDa in the three developmental stages examined. Immunohistochemistry data demonstrate that AQP1 was clearly expressed in the ectodermal and endodermal epithelia, the vascular endothelium, and the VSMCs. Because little information is available on the behavior of microvessel AQP1 during angiogenesis in normal and pathological conditions, our data relative to the pattern of expression of AQP1 in CAM blood vessels in normal conditions may be considered a useful tool to further investigate its modifications in several experimental conditions implying a stimulation or an inhibition of angiogenesis in the CAM assay.