Trophoblast Cell Recovery from Angiogenesis-Tube Formation Assay for Differentiation Marker Expression Analysis

During placenta development, extravillous trophoblast (EVT) cells invade the maternal decidua to remodel the uterine spiral arteries by a process of mesenchymal to endothelial-like transition. Traditionally, this process is evaluated by an in vitro tube-formation assay, where the cells organize themselves into tube-like structures when seeded over a polymerized basement membrane preparation. Although several structural features can be measured in photomicrographs of the structures, to assess the real commitment of EVT to the endothelial-type phenotype, biochemical analysis of cell extracts is required. Scraping the cells from the culture dish to obtain RNA and/or protein extracts is not an alternative since the tube-like structures are severely contaminated by the bulk of proteins from the polymerized basement membrane. Thus, a strategy to separate the cells from the basement membrane proteins prior to the preparation of cell extracts is needed. Here, a simple, fast, and cost-effective method to recover the tube-like structures from the in vitro tube-formation assay and the subsequent analysis by biochemical techniques is presented. Tube-like structures formed by HTR8/SVneo cells, an EVT cell line, were liberated from the polymerized basement membrane by a short incubation with PBS supplemented with ethylenediaminetetraacetic acid (EDTA). After serial washes, a ready-to-use pellet of purified tube-like structures can be obtained. This pellet can be subsequently processed to obtain RNA and protein extracts. qPCR analysis evidenced the induced expression of VE-cadherin and alphav-integrin, two endothelial cell markers, in EVT-derived tube-like structures compared to control cells, which was consistent with the induction of the endothelial cell marker, CD31, evaluated by immunofluorescence. Western blot analysis of the tube-like structures' protein extracts revealed the overexpression of RECK in transfected HTR8/SVneo cells. Thus, this simple method allows to obtain cell extracts from the in vitro tube-formation assay for the subsequent analysis of RNAs and protein expression.