High-mobility group box protein 1 and its signalling receptors in human preterm and term cervix

The objective of this study was to identify possible changes in mRNA and protein expression of high-mobility group box protein 1 (HMGB1) and its suggested receptors - receptor for advanced glycation end-products (RAGE) and Toll-like receptor 2 (TLR2) and TLR4 - in human cervix during pregnancy, term and preterm labor. Cervical biopsies were taken from 58 women: 20 at preterm labor, 24 at term labor, 10 at term not in labor and 4 from non-pregnant women. Real-time RT-PCR was used to quantify mRNA expression, and immunohistochemistry and ELISA for protein analysis. HMGB1, RAGE, TLR2 and TLR4 proteins were localized and their mRNA expression was detected in the cervix. There was more extranuclear HMGB1 in the cervical epithelium and stroma in preterm and term labor compared to the term not in labor. TLR2 mRNA expression was upregulated 5-fold in term labor and 3-fold in preterm labor compared to term not in labor and non-pregnant controls. There was lower expression of TLR2 and TLR4 mRNAs in preterm labor compared to term. Lower mRNA expression of HMGB1 was found in the subgroup with preterm premature rupture of membranes than in the rest of the preterm group, where levels were significantly higher than in term labor. In conclusion, extranuclear expression of HMGB1 during labor suggests a possible role of HMGB1 during the process of cervical ripening. Changes in expression of mRNAs encoding HMGB1, TLR2 and TLR4 in preterm labor suggest differences in the mechanism of cervical ripening at preterm and term delivery.