Spatiotemporal expression of α1, α3 and β1 integrin subunits is altered in rat myometrium during pregnancy and labour

Abstract

Integrins are transmembrane extracellular matrix (ECM) receptors composed of α- and β-subunits. Integrins can cluster to form focal adhesions and, because there is significant ECM remodelling and focal adhesion turnover in the rat myometrium during late pregnancy, we hypothesised that the expression of α1, α3 and β1 integrin subunits in the rat myometrium would be altered at this time to accommodate these processes. Expression of α1 and β1 integrin subunit mRNA was significantly increased on Days 6–23 of pregnancy compared with non-pregnant (NP) and postpartum (PP) time points (P < 0.05). In contrast, α3 integrin subunit mRNA expression was significantly increased on Days 14, 21 and 22 compared with NP, Day 10, 1 day PP and 4 days PP (P < 0.05). A relative gene expression study revealed that, of the integrins studied, the expression of β1 integrin mRNA was highest in pregnant rat myometrium. The α1, α3 and β1 integrin subunit proteins became immunolocalised to myocyte membranes in situ by late pregnancy and labour in both myometrial muscle layers. Increased α1, α3 and β1 integrin gene expression during gestation and the specific detection of these subunits in myocyte membranes during late pregnancy and labour may contribute to the cell–ECM interactions required for the development of a mechanical syncytium.