Seminal plasma enhances and accelerates progesterone-induced decidualisation of human endometrial stromal cells

In preparation for embryo implantation, endometrial stromal cells (ESC) undergo differentiation, termed decidualisation. Enhancing endometrial decidualisation may overcome reduced endometrial receptivity, a major limiting factor in natural and assisted reproduction. To determine whether seminal plasma (SP) influences decidualisation, primary human ESC were treated with progesterone (P-4, 50 ng mL(-1)) in the presence or absence of dialysed SP (0.5%) for 24 h or for up to 27 days to investigate immediate early effects or the effects of prolonged exposure, respectively. Combined SP and P-4 treatment induced ESC morphological differentiation. Relative to control, P-4 alone, and SP alone combined treatment with SP and P-4 for 27 days significantly upregulated 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 and P-4 treatment relative to control, P-4 alone and SP alone. Likewise, IGFBP1 secretion was significantly greater relative to control and P-4 alone over the course of 27 days. Thus, SP enhances and accelerates P-4-mediated decidualisation of human ESC and may enhance endometrial receptivity.