Transcriptomic analysis of the interaction of choriocarcinoma spheroids with receptive vs. non-receptive endometrial epithelium cell lines: an in vitro model for human implantation

The aim of this study was to establish an in vitro model to investigate the initial stages of human implantation based on co-culture of a) immortalized cells representing the receptive (Ishikawa) or non-receptive (HEC-1-A) endometrial epithelium with b) spheroids of a trophoblastic cell line (JEG-3) modified to express green fluorescent protein. After co-culturing Ishikawa cells with trophoblast spheroids, 310 and 298 genes increased or decreased their expression compared to non-co-cultured Ishikawa control cells, respectively; only 9 genes (5 increased and 4 decreased) were differentially expressed in HEC-1-A upon co-culture with trophoblast spheroids. Compared to HEC-1-A, the trophoblast challenge to Ishikawa cells differentially regulated the expression of 495 genes. In summary, upon co-culture with the trophoblast spheroids, non-receptive epithelium is characterized by a muted transcriptional response which in turn fails to activate the full transcriptional response that trophoblast spheroids undergo when co-cultured with receptive epithelium. GFP expressing JEG-3 spheroids were co-cultured with confluent monolayers of receptive Ishikawa or non-receptive HEC-1-A epithelia. After 48 hours of co-culture, GFP+ (trophoblast JEG-3 spheroid cells) and GFP- cell fractions (receptive Ishikawa or non-receptive HEC-1-A epithelial cells) were isolated by fluorescence-activated flow cytometry (FACS). The specific transcriptional changes of the isolated cell populations were analyzed by RNA-seq profiling. Statistical significance of gene expression differences was set at an absolute log2 fold change (log2FC) ≥1 and an adjusted p-value <0.05.