Figure 4.

Effects of ambient O₂ on cell fusion and expression of fusion–related proteins in primary human peri-term villous cytotrophoblast cell cultures. (A) Expression of fusion-associated genes using semi-quantitative RT-PCR under various O₂ conditions. Gels have been cropped exactly as in Fig. 3A for clarity, conciseness and comparison. (B) Detection of SUPYN protein by a SUPYN-specific ELISA. Data represent relative fold change compared with 3 H timepoint. Experiments were performed using 4 independent placenta samples, each in duplicate. Statistical analysis was performed using the Mann Whitney U test with Bonferroni correction. Values represent means ± SDs (n = 4). Statistical significance (*p < 0.05, **p < 0.01) compared with the 20% O₂ condition at each time point. (C) Fusion indices for cells grown under 2% to 20% O₂ conditions. 4 independent microscopic views were used to calculate fusion rates and paired-t-tests were used for statistical analysis. Values represent means ± SDs (n = 4) Statistical significance (*p < 0.05) compared with the 2% O₂ condition. (D) Expression of SUPYN protein in primary cytotrophoblast cells cultured for 96 H in various O₂ environments. Fluorescence immunocytochemistry analyses show an overlay with SUPYN protein (red), E-cadherin (green) and nucleus (blue). The scale bar = 50 micrometers. ASCT2–Alanine, Serine, Cysteine Transporter 2, the syncytin 1 receptor; MFSD2–major facilitator superfamily domain-containing protein 2, the syncytin 2 receptor; hCG–human chorionic gonadotropin.