OBJECTIVERecent progress in developmental biology has shown that the thyroid transcription factor-1 (TTF-1) plays an important role in lung development. The aim of this study was to investigate the expression and distribution of TTF-1 and its function during the development of epithelial stem cells in fetal human lungs.

METHODSHuman lung tissues were obtained with parental consent from 32 fetuses (10-27 weeks) and from seven newborn infants (28-36 weeks) who had not died from pulmonary diseases. The expression of TTF-1 was examined by immunohistochemistry.

RESULTSTTF-1 was expressed in the nuclei of columnar nonciliated epithelial cells of the fetal human lung as early as 10 weeks of gestation. With the development of bronchus TTF-1 positive cells were present in scattered nonciliated cells and were predominantly expressed in the nuclei of epithelial cells of the distal tubules and lung buds. By the late phase of fetal development or neonatal period, TTF-1 was expressed in only type II alveolar epithelium cells and their precursor cells but was absent in ciliated cells and type I alveolar epithelium cells.

CONCLUSIONSTTF-1 can stimulate the growth of both bronchial trees and alveolar cells and regulate the type II alveolar epithelium cells and their precursors to secret surfactants.