Localization of Epidermal Growth Factor Receptor in Alveolar Epithelium During Human Fetal Lung Development in Vitro

Abstract

Epidermal growth factor (EGF) enhances alveolar type II cell differentiation. In human fetal lung explants, EGF stimulates surfactant protein A (SP-A) synthesis. This effect may occur through a direct interaction of the ligand on EGF receptors located within distal pulmonary epithelium during alveolar type II cell differentiation. To determine if EGF receptor is present in alveolar epithelium, immunostaining for EGF receptor and in situ hybridization for EGF receptor mRNA were performed in human fetal lung explants undergoing alveolar type II cell differentiation in vitro. After 4 days in culture, EGF receptor immunostaining was present in alveolar epithelium from human fetal lung explants compared to minimal immunostaining in undifferentiated human fetal lung epithelium prior to culture. In situ hybridization revealed increased EGF receptor mRNA in differentiated type II cells from cultured explants, with minimal EGF receptor mRNA detected in undifferentiated epithelium from tissue prior to culture. Immunogold staining revealed EGF receptors on the cytoplasmic membranes of epithelial cells lining the prealveolar ducts in human fetal lung explants after 2 days in culture. Alveolar type II cell differentiation in vitro was confirmed ultrastructurally by the presence of lamellar bodies and biochemically by an increase in SP-A content. Thus, EGF receptor is found in alveolar epithelium during differentiation, which suggests an important role for EGF during human fetal lung development.

The proliferative effects of retinoic acid on primary cultures of adult rat type II pneumocytes depend upon cell density

“…Previously, others have demonstrated that RA increased EGFRs in kidney epithelial cells (Kawaguchi et al 1994), fetal lung cell lines (Oberg et al 1988;Oberg and Carpenter 1991), and mouse fibroblast lines (Jetten 1980). The isolation of EGFRs from the membrane surface of the type II pneumocyte in the present study is consistent with the localization of the receptor in the alveolar epithelium as reported by others (Klein et al 1995;Rice et al 1999). While RA did increase expression of the EGFR in the ELISA at high cell density (1×10 5 cells/well), it inhibited thymidine incorporation at high cell density.…”

“…Alveolar cells express both EGF and EGFR proteins (Raaberg et al 1991;Raaberg et al 1992;Klein et al 1995). To our knowledge, no information is available on regulation of EGFRs by RA in adult type II pneumocytes.…”

“…EGF is present in the lungs during developmental stages (Raaberg et al 1991), and EGF and its receptor are localized in the alveolar epithelium (Klein et al 1995). EGF is a natural ligand for the EGFR, and its mechanism of action is thought to occur through binding to the EGFR, increasing the tyrosine kinase activity of the receptor, and subsequently triggering a cascade of intracellular events leading to increased DNA synthesis and cell proliferation (Rice et al 1999).…”

Antisense Inhibition of Epidermal Growth Factor Receptor Decreases Expression of Human Surfactant Protein A

“…Furthermore, messenger RNA (mRNA) for both ligands is found in mesenchymal tissue from human fetal lung throughout gestation (17), observations suggestive of a paracrine effect of EGF/TGF-␣ on alveolar type II cell differentiation. EGF receptor protein and mRNA are found in alveolar epithelium from midtrimester human fetal lung explants that have undergone spontaneous differentiation in vitro (19). Thus, the presence of EGF receptor and its ligands in distal pulmonary epithelium during human fetal lung development suggests a regulatory role for EGF in type II cell differentiation.…”

The lungs in congenital diaphragmatic hernia: Do we understand?

“…This process depends on interaction between epithelium and mesenchyme 32 as first described in 1976 33 and with further support provided by recent studies in transgenic mice. 34 The control of growth of airways and epithelium is mediated by extracellular matrix (ECM) molecules, 35,36 transcription factors, 5,32,[37][38][39] growth factors, [40][41][42][43][44][45] neuropeptides, [46][47][48][49] fetal lung liquid, 50,51 and mechanical stress elicited by respiratory movements. 52,53 However, the clinical significance of these factors and their interactions are still under study.…”