Elucidation of the factors that regulate maintenance of the adult lung elastin matrix, including a better understanding of the role played by fibroblasts and by Hox5 genes, will ultimately lead to better treatments for lung disease diseases related to lung mesenchymal behavior such as BPD, emphysema, and idiopathic pulmonary fibrosis (IPF). Here, ELN is linked to idiopathic pulmonary fibrosis.