Recent evidence suggests that immune cell activity in the decidua is controlled by decidual stromal cells, which promote immune tolerance and shelter the fetus from the maternal immune system while maintaining maternal immune responses. The protective function of the decidua wanes at term leading to decidual activation triggering labour. However, the mechanisms remain unknown. We hypothesised that labour-promoting inflammatory genes in the decidual cells are regulated epigenetically by the BET family of epigenetic reader proteins which specifically recognize lysine-acetylated histones at gene regulatory regions of the chromatin via bromodomains (BRDs).
Decidual stromal cells were purified by Percoll density centrifugation followed by magnetic immune-selection and cultured under appropriate conditions. Purity was confirmed by flow-cytometry and immunocytochemistry. Cultures were treated with the selective BET-BRD inhibitors (+)-JQ1, I-BET-762 and the inactive control compound (-)-JQ1 at 0.5-1 mM as per Structural Genomics Consortium (SGC) guidelines for 48h and subsequently stimulated with lipopolysaccharide (LPS, 1 mg/ml) for 24h. The expression of the prostaglandin synthetic enzymes (PTGS1, PTGS2, PGES), inflammatory factors (IL6, IL8, TNF-a) and anti-inflammatory factors (IL10and IDO-1)was determined by qRT-PCR.
LPS stimulated robustly the expression of PTGS2,IL6, IL8, IL10and IDO-1, moderately the expression of PGESand TNF-a and had no effect on PTGS1. The BET-BRD inhibitors reduced LPS-induced expression of PTGS2,PTGES,IL6, IL8, IL10, TNF-a and IDO-1while PTGS1expression was unaffected. The control probe ((-)-JQ1) was ineffective. We have also found that decidual stromal cells express high levels of the BET-BRD family members BRD2 and BRD4, but low levels of BRD3. These results indicate that the acetyl-histone binding epigenetic reader proteins, especially BRD2 and BRD-4, participate in the regulation of key labour-associated genes in term decidua. We anticipate that histone acetylation is an epigenetic mechanism that controls decidual stromal cell function during pregnancy and labour.