Local injury of the endometrium induces an inflammatory response that promotes successful implantation

Objective: To study whether an injury-induced inflammation might be the mechanism underlying the favorable effect of endometrial biopsy on the implantation rate in in vitro fertilization (IVF) patients. Design: Controlled clinical study. Setting: A medical center IVF unit and a research institute. Patient(s): Women undergoing IVF who had previous failed treatment cycles. Intervention(s): Endometrial samples were collected from two groups of patients on day 21 of their spontaneous menstrual cycle. The experimental, but not the control group underwent prior biopsy treatment on days 8 or/and 11 to 13 of that same cycle. Main Outcome Measure(s): Abundance of immune cells, cytokines/chemokines level, correlation between these parameters and pregnancy outcome. Result(s): A statistically significantly higher amount of macrophages/dendritic cells (HLA-DR⁺ CD11c⁺ cells) and elevated proinflammatory cytokines, tumor necrosis factor-α (TNF-α), growth-regulated oncogene-α (GRO-α), interleukin-15 (IL-15), and macrophage inflammatory protein 1B (MIP-1B), were detected in day-21 endometrial samples of the experimental group. A direct stimulatory effect of TNF-α on MIP-1B, GRO-α, and IL-15 messenger RNA (mRNA) expression was demonstrated. A positive correlation was found between the levels of macrophages/dendritic cells, MIP-1B expression, and TNF-α expression and the pregnancy outcome. Conclusion(s): A biopsy-induced inflammatory response may facilitate the preparation of the endometrium for implantation. Increased MIP-1B expression could possibly serve for prediction of implantation competence.