Seminal Plasma Enhances and Accelerates Progesterone-Induced Decidualization of Human Endometrial Stromal Cells

In preparation for embryo implantation endometrial stromal cells (ESC) undergo differentiation, termed decidualization. Enhancing endometrial decidualization may overcome reduced endometrial receptivity, a major limiting factor in natural and assisted reproduction. To determine whether seminal plasma (SP) influences decidualization, primary human ESC were treated with progesterone (P4, 50 ng/ml) in the presence or absence of dialysed SP (0.5%) for 24 hours or for up to 27 days to investigate immediate early effects or the effects of prolonged exposure, respectively. Combined SP & P4 treatment induced ESC morphological differentiation. Relative to control, P4 alone, and SP alone, combined treatment with SP & P4 for 27 days significantly up-regulated mRNA levels of the decidua-specific markers prolactin (PRL) and insulin-like growth factor binding protein 1 (IGFBP1). Consistently, PRL protein secretion was significantly increased over the course of 27 days combined SP & P4 treatment relative to control, P4 alone and SP alone. Likewise, IGFBP1 secretion was significantly greater relative to control and P4 alone over the course of 27 days. Thus, SP enhances and accelerates P4-mediated decidualization of human ESC and may enhance endometrial receptivity