Problem: Are toll-like receptors (TLRs) expressed by human endometrium and endometrial cell lines?
Methods of study: Expression of each TLR mRNA species was determined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of proliferative-phase human endometrium, separated endometrial epithelial cells, and the Ishikawa and RL95-2 endometrial epithelial cell lines. U-937 and SKW 6.4 cell lines were used as positive controls. Functional relevance of PCR findings was tested by enzyme-linked immunsorbent assay (ELISA)analysis of IL-8 production after stimulating cell lines with ligands for TLR2-5.
Results: TLR1-6 and 9 mRNA species were detected in both whole endometrium and separated endometrial epithelial cells. Ishikawa cells expressed TLR2 and TLR5, while RL95-2 cells expressed TLR3, 5, and 9. Response of RL95-2, Ishikawa, and U-937 cells to TLR2-5 ligands was consistent with RT-PCR findings except response to flagellin by Ishikawa cells.
Conclusion: These studies provide the first evidence of TLR expression in the endometrium of any species and suggest the usefulness of endometrial cell lines to study TLR function.