The extent and variability of effects of culture conditions on the secretion of human chorionic gonadotrophin and interleukin-6 by human, term placental explants in culture

Abstract

Culture of explants derived from third trimester human placenta is used in a range of contexts as an experimental model that retains tissue architecture. This study aimed to explore the variability between, and within, individuals of secretion by explants of human chorionic gonadotrophin (hCG) and interleukin-6 (IL-6). Standard culture medium contained hydrocortisone, insulin, retinoic acid and serum. Under these conditions explants displayed significant differences in the time-course and extent of hCG secretion. Peak hCG secretion varied between 1.19 and 242 mIU/mg protein/h (coefficient of variation (CV) = 111%) and could occur between days 4 and 7 of culture. hCG secretion was more variable if explant protein was <400 μg. Unadjusted day 7 hCG secretion showed marked variation: intra-placental CV = 15%, inter-placental CV = 86%. When day 7 hCG secretion was standardised by day 6 secretion, intra-placental CV was 6.9%, inter-placental CV was 4.0%. When this standardisation was applied, hCG secretion during day 7 of culture was not affected by removal of hydrocortisone, insulin or serum from the medium or by the addition of tumour necrosis factor-α (TNF-α). The secretion of IL-6 during day 7 of culture (standardised by taking natural logarithms) was increased markedly by the addition of TNF-α but unaltered by removing hydrocortisone, insulin or serum. Thus, we have shown that although variable, secretion by placental explants can be used to investigate how placental tissue adapts to different culture conditions. However, explants of the same protein content may have markedly different secretory properties.