Toll-Like Receptor 4 Expression in Decidual Cells and Interstitial Trophoblasts Across Human Pregnancy

Problem Toll-like receptor-4 (TLR-4) protects against Gram-negative bacteria expressed lipopolysaccharide and danger signals from injured or dying cells. Although decidual cells (DCs) and interstitial trophoblasts (ITs) are in close contact, TLR-4 has been studied extensively only in ITs. Method of study Formalin-fixed, paraffin-embedded serial sections of endometrium in follicular and luteal phases and deciduas from first and second trimester elective terminations and third trimester normal deliveries were immunostained for TLR-4, trophoblast-specific cytokeratin, and DC-specific vimentin. HSCORE assessed TLR-4 immunostaining in DCs versus ITs. Results TLR-4 HSCORES were significantly higher in: (i) first trimester DCs than luteal phase pre-decidual stromal cells; (ii) first and third versus second trimester DCs, but similar between third trimester deciduas parietalis and basalis; (iii) first versus second trimester ITs; (iv) DCs versus ITs across gestation. Conclusion Higher TLR-4 in DCs than ITs suggests DCs as primary targets for Gram-negative bacteria and/or inflammation-related danger signals.