TLR-1, TLR-2, and TLR-6 MYD88-dependent signaling pathway: A potential factor in the interaction of high-DNA fragmentation human sperm with fallopian tube epithelial cells.

Objective: The DNA integrity of spermatozoa that attach to fallopian tube (FT) cells is higher than spermatozoa that do not attach. FT epithelial cells can distinguish normal and abnormal sperm chromatin. This study investigated the effects of sperm with a high-DNA fragmentation index (DFI) from men with unexplained repeated implantation failure (RIF) on the Toll-like receptor (TLR) signaling pathway in human FT cells in vitro.

Methods: Ten men with a RIF history and high-DFI and 10 healthy donors with low-DFI comprised the high-DFI (>30%) and control (<30%) groups, respectively. After fresh semen preparation, sperm were co-cultured with a human FT epithelial cell line (OE-E6/E7) for 24 hours. RNA was extracted from the cell line and the human innate and adaptive immune responses were tested using an RT2 profiler polymerase chain reaction (PCR) array.

Results: The PCR array data showed significantly higher TLR-1, TLR-2, TLR-3, TLR-6, interleukin 1α (IL-1α), IL-1β, IL-6, IL-12, interferon α (IFN-α), IFN-β, tumor necrosis factor α (TNF-α), CXCL8, GM-CSF, G-CSF, CD14, ELK1, IRAK1, IRAK2, IRAK4, IRF1, IRF3, LY96, MAP2K3, MAP2K4, MAP3K7, MAP4K4, MAPK8, MAPK8IP3, MYD88, NFKB1, NFKB2, REL, TIRAP, and TRAF6 expression in the high-DFI group than in the control group. These factors are all involved in the TLR-MyD88 signaling pathway.

Conclusion: The MyD88-dependent pathway through TLR-1, TLR-2, and TLR-6 activation may be one of the main inflammatory pathways activated by high-DFI sperm from men with RIF. Following activation of this pathway, epithelial cells produce inflammatory cytokines, resulting in neutrophil infiltration, activation, phagocytosis, neutrophil extracellular trap formation, and apoptosis.