Interleukin (IL)-1 Beta and IL-6 Levels in Human Embryo Culture Supernatants and their Role in Implantation Following IVF: A Prospective, Non-randomized Study

Objective: Interleukin-1 beta (IL-1β) and Interleukin-6 (IL-6) are pro-inflammatory cytokines involved in the mother-embryo interaction during blastocyst adhesion and invasion into the endometrium. IL-1β is also considered as a first signal delivered from blastocyst to the endometrium to influence uterus receptivity. The aim of the present prospective, non-randomized study was to explore whether the measurement of IL-1β and IL-6 secretion by blastocysts could serve as a non-invasive method to predict blastocyst implantation competence following in vitro fertilization (IVF). Methods: IL-1β and IL-6 were measured in the supernatant culture media of 683 blastocysts transferred into 245 women following IVF cycles, and their levels were correlated with implantation and pregnancy rates per transfer. Measurements were performed using a Luminex 200 and commercially available interleukin kits. Statistical analyses were performed using GraphPad Prism 5 software, and a probability of p<0.05 was used to indicate a significant difference. Results: IL-1β was detected in 26.5% of the blastocyst supernatants (179/683), with a mean value 0.099 pg/ml, and IL-6 was detected in 20.35% of blastocysts (139/683), with a mean value of 0.046 pg/ml. Cytokine levels showed no correlation with blastocyst quality or developmental stage. The mean values of IL-1β and IL-6 in the implanted blastocysts were 0.073 and 0.036 pg/ml, respectively. In the non-implanted blastocysts, the corresponding values were 0.0141 and 0.060 pg/ml. The pregnancy and implantation rates in women with detectable IL-1β levels (pregnancy rate (PR): 56.3%; implantation rate (IR): 21.8%) and non-detectable IL-1β levels (PR: 60.23%; IR: 28.37%) and in women with detectable IL-6 levels (PR: 58%; IR: 25%) and non-detectable IL-6 levels (PR: 59.5%; IR: 26.83%) were not significantly different. Conclusion: Blastocysts secrete IL-1β, and to a lesser extent, IL-6. No significant differences in implantation or pregnancy outcomes were identified between patients with detectable and undetectable IL-1β and IL-6 levels. Therefore, the non-invasive measurement of IL-1β and IL-6 secreted by blastocysts prior to transfer should not be considered a useful biomarker of blastocyst development and implantation competence.