Preservation of the characteristics of the cultured human type II alveolar epithelial cells.
The human type II alveolar epithelial cells lost their specific characteristics during cultivation. We examined the ultrastructural and biochemical nature of the human type II cells cultured by two culture systems. To make a physiological alveoli model, the epithelial cells were seeded onto the cell culture insert and allowed contact with the air directly. The cells exposed to the air expressed polarity and immature lamellar bodies in their cytoplasm. Separately, the alveolar epithelial cells were cultured as spheroids to construct the three-dimensional condition. These cells expressed mature morphological characteristics as epithelial cells and lamellar bodies. The expression of the surfactant apoprotein-A (SP-A) and -C (SP-C) mRNA was compared in the cells cultured as a monolayer, the air exposed and the spheroids. SP-A mRNA was detected in all the cultured epithelial cells, but SP-C mRNA, a specific protein for the type II cells, was expressed only in the cells forming spheroids. The expression of uPA, one of the fibrinolytic enzymes, its receptor (uPAR) and its inhibitor-1 (PAI-1) were also examined. The epithelial cells exposed to the air and formed spheroids expressed a larger amount of uPA mRNA than the monolayer, although the amount of uPAR mRNA were comparable in these cells. The amount of PAI-1 mRNA significantly increased when the epithelial cells were exposed to the air. These results indicate that the type II alveolar epithelial cells induced and preserved their specific characteristics by taking the physiological three-dimensional structure, and these characteristics were partially restored by exposure to the air. Those findings suggest that the alveolar epithelial cells should be cultivated in three-dimensional form with contact to the air to regenerate an appropriate alveolar tissue.
Takahashi
Kimiko
K
Fifth Department of Internal Medicine, Kasumigaura Hospital Tokyo Medical University, 3-20-1, Chuo, Ami, Inashiki, Ibaraki 300-0395, Japan. kimikot@tokyo-med.ac.jp
Mitsui
Masako
M
Takeuchi
Kyoko
K
Uwabe
Yasuhide
Y
Kobayashi
Katsuyuki
K
Sawasaki
Yoshio
Y
Matsuoka
Takeshi
T
D001059:Apoproteins / Q000096:biosynthesis; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured; D006801:Humans; D010960:Plasminogen Activators / Q000096:biosynthesis; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000648:ultrastructure*; D037661:Pulmonary Surfactant-Associated Proteins / Q000096:biosynthesis; D020545:Respiratory Mucosa / Q000378:metabolism / Q000648:ultrastructure*; D018874:Spheroids, Cellular / Q000648:ultrastructure; D014021:Tissue Preservation / Q000379:methods*
D001059:Apoproteins; D037661:Pulmonary Surfactant-Associated Proteins; C046616:pulmonary surfactant apoprotein; D010960:Plasminogen Activators