title: Mechanical distention modulates alveolar epithelial cell phenotypic expression by transcriptional regulation.
abstract: The development of a normal pulmonary alveolar epithelium, essential for gas exchange, is critical for the successful adaptation to extrauterine life. From observations of natural and experimental developmental abnormalities, it has been hypothesized that mechanical factors may play a role in regulating differentiation of the pulmonary alveolar epithelium. To test this hypothesis directly, we have investigated the in vitro effects of mechanical distention on the expression of specific markers for the type I and type II cell phenotypes. Fetal rat lung (18-d) explants were mechanically distended in culture for 18 h. Mechanical distention caused an increase in RTI 40 messenger RNA (mRNA), a marker of the type I cell phenotype, of 10.6 times (n = 3, P < 0.05) that of undistended controls. In contrast, mechanical distention resulted in a decrease in mRNA content of two markers of the type II cell phenotype, surfactant protein (SP)-B and SP-C. SP-B was reduced to 10 +/- 9% (n = 3, P < 0.005) and of SP-C to 12 +/- 7% (n = 3, P < 0.0001) of undistended controls. Mechanical distention had no effect on content of mRNA for SP-A or 18S ribosomal RNA. Examined by nuclear run-on assays, mechanical distention caused changes in transcriptional rates of RTI 40, SP-B, and SP-C. These data show that mechanical distention stimulates expression of a type I cell marker and inhibits expression of markers for the type II phenotype; these effects occur at least in part at the transcriptional level. These studies support the hypothesis that mechanical distention of fetal lung tissue stimulates expression of the type I cell phenotype and inhibits expression of the type II phenotype.
authors.affiliation: Departments of Pediatrics and Medicine and the Cardiovascular Research Institute, University of California San Francisco, San Francisco, California, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Gutierrez
authors.forename: R
authors.initials: R
authors.lastname: Ertsey
authors.forename: L M
authors.initials: LM
authors.lastname: Scavo
authors.forename: E
authors.initials: E
authors.lastname: Collins
authors.forename: L G
authors.initials: LG
authors.lastname: Dobbs
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D008168:Lung / Q000196:embryology / Q000378:metabolism*; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000378:metabolism; D010641:Phenotype; D011510:Proteolipids / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D014158:Transcription, Genetic; D000098853:Podoplanin
chemical_list: D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012337:RNA, Ribosomal, 18S; C092025:Pdpn protein, rat; D000098853:Podoplanin