Developmental expression of SP-A and SP-A mRNA in the proximal and distal respiratory epithelium in the human fetus and newborn.
We used immunolocalization and in situ hybridization to determine the distribution of SP-A and SP-A mRNA in lungs of human fetuses and normal newborn infants. Early in the second fetal trimester a few immunostained cells were observed in tracheal epithelium, often in mucosal folds near the origin of submucosal gland ducts. Non-mucous tracheal gland cells were immunostained for SP-A as they became differentiated. Expression of SP-A mRNA was similar to that of immunolocalization in the second trimester. Immunostained cells and SP-A mRNA also appeared about the same time in gestation in isolated cells of bronchial epithelium and glands. SP-A mRNA was seen in bronchiolar cells and pre-Type II cells lining terminal airways of fetuses at 19-20 weeks of gestation. Only in liveborn infants did cells of bronchioloalveolar portals and mature Type II cells contain SP-A mRNA or immunostain for SP-A. In postnatal infants, luminal material was also stained for SP-A. Although some alveolar macrophages contained immunoreactive material, SP-A mRNA was never detected. The abundance of SP-A in tracheal and bronchial glands and epithelium of conducting airways supports the importance of non-surfactant-associated functions for SP-A and may be related to a role in host defense.
Khoor
A
A
Department of Pathology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2370.
Gray
M E
ME
Hull
W M
WM
Whitsett
J A
JA
Stahlman
M T
MT
D000367:Age Factors; D000375:Aging / Q000378:metabolism; D005260:Female; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007231:Infant, Newborn; D008168:Lung / Q000737:chemistry* / Q000196:embryology* / Q000378:metabolism; D009092:Mucous Membrane / Q000737:chemistry / Q000378:metabolism; D011247:Pregnancy; D011510:Proteolipids / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D014132:Trachea / Q000737:chemistry / Q000196:embryology / Q000378:metabolism
D006023:Glycoproteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger