EXTRACELLULAR MATRIX-DRIVEN ALVEOLAR EPITHELIAL CELL DIFFERENTIATION IN VITRO

• Published in: Experimental lung research 2005-06, Vol.31 (5), p.461-482
• Main Authors: Olsen, Colin E., Isakson, Brant E., Seedorf, Gregory J., Lubman, Richard L., Boitano, Scott
• Format: Article
• Language: English
• Subjects: Air breathing; alveolar cell differentiation; Animals; Biological and medical sciences; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cells, Cultured; collagen; Collagen - pharmacology; ECM; Epithelial Cells - cytology; Extracellular Matrix - physiology; Extracellular Matrix Proteins - pharmacology; Fundamental and applied biological sciences. Psychology; Laminin - pharmacology; lung epithelial repair; Male; Phenotype; Proteins - metabolism; Pulmonary Alveoli - cytology; Rats; Rats, Sprague-Dawley; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Vertebrates: respiratory system
• ISSN: 0190-2148; 1521-0499
• DOI: 10.1080/01902140590918830

During homeostasis and in response to injury, alveolar type II (AT2) cells serve as progenitor cells to proliferate, migrate, differentiate, and reestablish both alveolar type I (AT1) and AT2 cells into a functional alveolar epithelium. To understand specific changes in cell differentiation, we monitored morphological characteristics and cell--specific protein markers over time for isolated rat AT2 cells cultured on combinations of collagen, fibronectin and or laminin-5 (Ln5). For all matrices tested, cultured AT2 cells displayed reduced expression of AT2 cell--specific markers from days 1 to 4 and increased expression of AT1-specific markers by day 3, with continued expression until at least day 5. Over days 5 to 7 in culture, cells took on an AT1-like phenotype (on collagen fibronectin; collagen alone; or Ln5 alone), an AT2-like phenotype (on collagen fibronectin Ln5; or collagen Ln5), or both AT1-like and AT2-like phenotypes (on collagen fibronectin matrix with a subsaturating amount of Ln5). Cells transferred between matrices at day 4 of culture retained the ability to alter day 7 phenotype. We conclude that in vitro, (1) AT2 cells exhibited phenotypic plasticity that included an intermediate cell type with both AT1 and AT2 cell characteristics independent of day 7 phenotype; (2) both collagen and Ln5 were needed to promote the development of an AT2-like phenotype at day 7; and (3) components of the extracellular matrix (ECM) contribute to phenotypic switching of alveolar cells in culture. The described tissue culture models provide accessible models for studying changes in alveolar epithelial cell physiology from AT2 cell progenitors to the establishment of alveolar epithelial monolayers that represent AT1-like, AT2-like, or a mix of AT1- and AT2-like cells.