IMMUNOHISTOCHEMICAL LOCALIZATION OF CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR IN HUMAN FETAL AIRWAY AND DIGESTIVE MUCOSA

The cellular distribution of the cystic fibrosis transmembrane conduct ance regulator (CFTR) in human fetal digestive and respiratory mucosa has been studied by immunohistochemistry. The streptavidin-biotin immu noperoxidase method was applied to paraffin-embedded specimens collect ed from normal fetuses ranging from 7 to 39 wk of gestation. By the 7t h wk, CFTR protein was strongly detected in the yolk sack; in contrast , the staining was weak in the undifferentiated epithelium of the inte stine and the airways. At 12 wk, the intestine showed strongly and dif fusely stained enterocytes and a basal cytoplasmic reactivity in the f irst secretory cells. During development, only slight changes could be detected in the digestive epithelial distribution of CFTR. In the air ways, the CFTR distribution followed the cephalocaudal maturation. In the tracheal ciliated cells, the CFTR protein was diffusely detected i n the cytoplasm as early as 7 wk. After 24-25 wk, CFTR was localized a t the apical domain of the ciliated cells and was also present in the collecting ducts and in the glands of the airways, predominantly in th e periphery of the acini. Our data suggest that the CFTR is present as early as 7 wk during organogenesis and probably plays an important ro le during fetal life. There is an evolution in the CFTR distribution d uring airway development, whereas, in the intestine, CFTR is highly ex pressed through the epithelium as early as 12 wk and keeps the same di stribution until birth.