ESTROGEN-DEPENDENT EXPRESSION OF THE CYSTIC-FIBROSIS TRANSMEMBRANE REGULATOR GENE IN A NOVEL UTERINE EPITHELIAL-CELL LINE

We have demonstrated previously the modulation of CFTR expression by e strogen in vivo in the rat uterine epithelium. The purpose of this stu dy was to establish a suitable in vitro system to investigate the regu lation of CFTR by steroid hormones. Primary cultures of rat uterine ep ithelial cells, which showed high levels of CFTR expression in vitro, were infected with an adeno/SV40 virus. One clone, UIT 1.16, which ret ained the morphology of the primary epithelial cells yet proliferated beyond the life span of the primary culture, was isolated and characte rized. Successful immortalization of UIT 1.16 cells was verified by th e presence of a band corresponding to the SV40 large T-antigen in west ern blots, as well as by their ability to proliferate continuously. Tr ansmission electron microscopy studies revealed that these cells maint ained the characteristics of a polarized epithelium with well-establis hed membrane domains and specialized intercellular junctions. A high t ransepithelial electrical resistance was also observed when cells were assayed in modified Ussing chambers. When the basolateral cellular me mbrane of cells grown in vitrogen-coated filters was permeabilized wit h nystatin, a forskolin-stimulated Cl- permeability was observed in th e apical membrane, similar to that present in other CFTR-expressing ep ithelial cells. UIT 1.16 cells showed high levels of CFTR expression o n northern blots. The expression of CFTR was dependent on the presence of estrogen in the culture medium, since almost undetectable levels o f CFTR mRNA were observed when the cells were cultured in medium conta ining serum depleted of steroid hormones. However, addition of estroge n to this medium prevented the disappearance of CFTR mRNA, confirming estrogen-regulated expression of CFTR in the UIT 1.16 cell line. The n ewly developed UIT 1.16 cell line provides a valuable model to analyze the regulation of CFTR expression by steroid hormones. Moreover, the cell line could also be used to investigate the role of CFTR in the ut erus during the normal female cycle as well as for the study of other uterine epithelial functions and the agents that regulate them.