Epithelial cell integrin ß1 is required for developmental angiogenesis in the pituitary gland.

As a key component of the vertebrate neuroendocrine system, the pituitary gland relies on the progressive and coordinated development of distinct hormone-producing cell types and an invading vascular network. The molecular mechanisms that drive formation of the pituitary vasculature, which is necessary for regulated synthesis and secretion of hormones that maintain homeostasis, metabolism, and endocrine function, remain poorly understood. Here, we report that expression of integrin ß1 in embryonic pituitary epithelial cells is required for angiogenesis in the developing mouse pituitary gland. Deletion of pituitary epithelial integrin ß1 before the onset of angiogenesis resulted in failure of invading endothelial cells to recruit pericytes efficiently, whereas deletion later in embryogenesis led to decreased vascular density and lumen formation. In both cases, lack of epithelial integrin ß1 was associated with a complete absence of vasculature in the pituitary gland at birth. Within pituitary epithelial cells, integrin ß1 directs a large transcriptional program that includes components of the extracellular matrix and associated signaling factors that are linked to the observed non-cell-autonomous effects on angiogenesis. We conclude that epithelial integrin ß1 functions as a critical and canonical regulator of developmental angiogenesis in the pituitary gland, thus providing insight into the long-standing systems biology conundrum of how vascular invasion is coordinated with tissue development.