RNA profiling of laser microdissected human trophoblast subtypes at mid-gestation

Human placental architecture is complex. Its surface epithelium, specialized for transport, forms by fusion of cytotrophoblast progenitors into multinucleated syncytiotrophoblasts. Near the uterine surface, these progenitors assume a different fate, becoming cancer-like cells that invade its lining and blood vessels. The latter process physically connects the placenta to the mother and shunts uterine blood to the syncytiotrophoblasts. Isolation of trophoblast subtypes is technically challenging. Upon removal, syncytiotrophoblasts disintegrate and invasive cytotrophoblasts are admixed with uterine cells. We used laser capture to circumvent these obstacles. This enabled isolation of syncytiotrophoblasts and two subpopulations of invasive cytotrophoblasts—cell column and endovascular. Transcriptional profiling revealed numerous genes whose placental or trophoblast expression was not known, including neurotensin and C4ORF36. Using mass spectrometry, discovery of differentially expressed mRNAs was extended to the protein level. We also found that invasive cytotrophoblasts expressed cannabinoid receptor 1. Unexpectedly, screening agonists and antagonists showed signals from this receptor promote invasion. Together these results revealed novel gene expression patterns that translate to the protein level. Our data also suggested that endogenous and exogenous cannabinoids can affect human placental development. This was a cross-sectional analysis of placentas collected at mid-gestation(n=4). Laser microdissection enabled the isolation of samples that were enriched for syncytiotrophoblasts, villus cytotrophoblasts or endovascular cytotrophoblasts. A microarray approach was used for global transcriptional profiling.