Laminin and β1 integrin distribution in the early stages of human kidney development

Laminin, an extracellular matrix molecule (EMM) widely expressed in the basal laminae, interacts with specific membrane receptors among which the integrin molecules are the best known. During embryo development laminin is the first synthesized EMM and plays a significant role in the morphogenesis of organs in which epithelial-mesenchymal interactions and branching take place. The present study describes the distribution of laminin and of beta-1 integrin receptors during the very early stages of human kidney development. The observations were carried out on paraffin sections of human embryos ranging between the 4th and the 7th gestational week. Laminin was detected within the basement membranes of mesonephric duct, vesicles, glomerular vessels and celomic epithelium. The metanephric anlage reacted with anti-laminin immunoglobulins in the basement membrane underlying the ampullae and in few blastemic cap cells. Low levels of beta-1 integrin reactivity were found in both the mesonephric and metanephric structures. This study provides for the first time data about the distribution of laminin and beta-1 integrin in the early stages of human renal organogenesis suggesting a key role for these molecules in the epithelial-mesenchymal interactions necessary for kidney development.