Identification of extracellular matrix components and their integrin receptors in the human fetal adrenal gland

The development of the human fetal adrenal gland is characterized by a grad ient of mitotic activity, cell migration, and cell apoptosis, all of which dictate its particular function. Such plasticity may possibly be under the control of the extracellular environment. The goal of this study was to ide ntify components of the extracellular matrix in second-trimester fetal adre nal glands. Whereas collagen TV was expressed evenly throughout the gland, both fibronectin and laminin demonstrated a mirror-imaged distribution, wit h higher expression of fibronectin in the central portion and laminin at th e periphery of the gland. The integrin subunit alpha1 was found mainly in t he definitive zone and the alpha2-subunit mainly in the transitional zone, whereas integrin alpha3 (which binds both fibronectin and laminin) was dete cted only in the fetal zone. The beta2-subunit was observed solely in chrom affin cells. Such specific gradients of integrin and MEC component expressi on suggest that the extracellular environment does play a definite role dur ing adrenal gland development. Indeed, compared with that in untreated plas tic dishes, ACTH stimulation of dehydroepiandrosterone sulfate and cortisol was enhanced by collagen IV. In addition, fibronectin enhanced dehydroepia ndrosterone sulfate but decreased cortisol secretion, compared with collage n IV substrates. These results provide fundamental insight into the contrib ution of the microenvironment in cellular processes leading to fetal adrena l gland development.