Quantitative real-time polymerase chain reaction (qRT-PCR) analysis
Total RNA was isolated from human placentas and cells via an RNA isolation kit (TIANGEN, Beijing, China) following the manufacturer′s instructions. Following quantification of the RNA, cDNA was synthesized via a reverse transcription kit (Takara, Tokyo, Japan). The cDNA was subsequently subjected to real-time PCR amplification in a thermal cycler via TBGreen Fast qPCR mix (Takara, Tokyo, Japan). All experiments were performed in triplicate, and the data were normalized to those of GAPDH. The specific primer sequences are provided in Table S1.