Despite acceptance that alveolar basement membranes are critical to normal alveolar structure and function, there is limited information about the cellular sources and regulation of alveolar basement membrane components or about alveolar cell responses to alveolar basement membrane damage. Laminins are major components of basement membranes. Each laminin is a heterotrimer composed of an alpha, beta, and gamma chain. We will focus on recently-identified laminin alpha chains, alpha3A, alpha3B, alpha4, and alpha5, which are more prominent in adult mouse lung parenchyma than alpha1, the alpha chain in the much studied laminin-1. We will define the cellular expression of laminin alpha chains in lung through mouse development. We will determine the distribution of laminin alpha chains in alveolar walls using immunoelectron microscopy. Using alpha5 """"""""knockout"""""""" mice, which we have made, we will determine the effect of laminin alpha5 on lung development. We will compare laminin alpha5-deficiency with laminin beta2-deficiency using laminin beta2 """"""""knockout"""""""" mice, which we also have. In preliminary observations, we have found that TGFbeta1 and KGF up-regulate laminin alpha5 expression by alveolar epithelial cells. We will extend these observations to other laminin alpha chains and other lung cell types. We will use co-cultures to determine the effects of epithelial-mesenchymal interactions on laminin alpha chain expression. Because we hypothesize that the regulation of laminin alpha5 expression by TGFbeta1 and KGF is transcriptional, we will characterize the 5' end of the mouse laminin alpha 5 gene, including the promoter elements. We will determine the expression of laminin alpha chains in experimental alveolar damage and whether KGF affects expression of basement membrane components in models of alveolar damage. We will assess expression of basement membrane components in human alveolar damage using reagents we are developing specifically for human tissue. Preliminary studies show up- regulation of laminin alpha5 in human pulmonary fibrosis. We believe that better understanding of alveolar basement membrane biology will lead to improved capacity to monitor and influence lung damage and repair in conditions such as ARDS and idiopathic pulmonary fibrosis.
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