Culture of first-trimester and full-term human chorionic villus explants: role of human chorionic gonadotropin and human placental lactogen as a viability index

Abstract

In long-term cultures of human chorionic villus explants, the viability of the tissue must be controlled to ensure the reliability of functional studies. Ionic levels (pH), gas concentrations (pO2, pCO2) and metabolic markers (glucose, lactate) in the culture medium are often utilized. Analyses of hormone, enzyme and protein levels are also frequently used to estimate viability. The purpose of this study was to evaluate whether in vitro release and immunoreactivity of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) were correlated with the viability of first-trimester and full-term chorionic villus explants as determined by histopathology. Villus explants of first-trimester and full-term pregnancies were incubated in 6-well plates of RPMI medium which was supplemented with 10% fetal calf serum. Incubations were performed for 10 days, and the plates were kept at 37 degrees C under a water-saturated atmosphere containing 5% CO2 and 95% O2. The medium was replaced every day and samples of supernatant were frozen for later testing of hCG (first trimester) or hPL (full term), glucose consumption and lactate production. The tissue was also fixed and embedded for light-microscopic examination and immunocytochemistry. The hCG release remained stable during 6-7 days at a high level before decreasing, whereas hPL release decreased during the first 5-6 days then stabilized at a relatively low level. Only hCG kinetics were significantly different between tissue incubated with and without cycloheximide or iodoacetic acid. Both hCG and hPL immunoreactivity were not significantly different between tissue cultures with, and without, addition of cycloheximide or iodoacetic acid and even with morphological evidence of trophoblast and endothelial necrosis. The immunoreactivity for both hormones remains highly positive when the significant release has stopped, and does not reflect the tissue viability.