Establishment of an immortalized human extravillous trophoblast cell line by retroviral infection of E6/E7/hTERT and its transcriptional profile during hypoxia and reoxygenation

Investigation into the function of human trophoblasts has been largely restricted by a lack of suitable cell models. We aimed to produce normal human trophoblast cell lines with a long lifespan and to provide an ideal in vitro cell model. Primary human trophoblast cells were derived from a placenta that had undergone elective abortion at the 7th week of gestation. The cells were immortalized by infection with retroviral expression vectors containing the type 16 human papillomaviruses E6 and E7 in combination with human telomerase reverse transcriptase (hTERT). Characterization of the cell line was performed by immunocytochemistry using a panel of antibodies, Western blotting, real-time RT-PCR, an invasion assay, gelatin zymography, karyotype analysis and a nude mouse assay. Gene expression profiles under hypoxia (1% O2, 1 h) and subsequent reoxygenation (20% O2, 6 h) were analyzed using cDNA microarray. Immunocytochemistry revealed an extravillous trophoblastic phenotype by positive staining for hCGβ, cytokeratin 7, HLA-G and CD9. A transwell insert invasion assay showed the invasiveness of this cell line and gelatin zymography detected the secretion of MMP-2 and MMP-9. Karyotype analysis exhibited an almost normal chromosomal number which ranged from 46 to 48 and the cells showed no tumorigenecity in a nude mouse assay. Forty-three genes showing reversible up- or down-regulation during hypoxia were detected using an oligonucleotide array. This newly immortalized cell line, HChEpC1b, is a useful model for the study of extravillous trophoblast function.