Nuclear factor of activated T-cell isoform expression and regulation in human myometrium.

Evonne C Chin-Smith,Frances R Willey,Rachel M Tribe,Michael J Taggart,Donna M Slater

doi:10.1186/s12958-015-0086-0

Abstract

BackgroundDuring pregnancy, myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and ultimately prepare for the onset of labour. It is proposed that changes in calcium signalling, may contribute to regulating gene expression and that nuclear factor of activated T-cell (NFAT) transcription factors (isoforms c1-c4) may be involved. Currently, there is little information regarding NFAT expression and regulation in myometrium.MethodsThis study examined NFAT isoform mRNA expression in human myometrial tissue and cells from pregnant women using quantitative PCR. The effects of the Ca2+ ionophore A23187 and in vitro stretch (25 % elongation, static strain; Flexercell FX-4000 Tension System) on NFAT expression were determined in cultured human myometrial cells.ResultsHuman myometrial tissue and cultured cells expressed NFATc1-c4 mRNA. NFATc2 gene expression in cultured cells was increased in response to 6 h stretch (11.5 fold, P < 0.001, n = 6) and calcium ionophore (A23187, 5 μM) treatment (20.6 fold, P < 0.001, n = 6). This response to stretch was significantly reduced (90 %, P < 0.001, n = 10) in the presence of an intracellular calcium chelator, BAPTA-AM (20 μM).ConclusionsThese data suggest that NFATc2 expression is regulated by intracellular calcium and in vitro stretch, and that the stretch response in human myometrial cells is dependent upon intracellular calcium signalling pathways. Our findings indicate a potentially unique role for NFATc2 in mediating stretch-induced gene expression per se and warrant further exploration in relation to the mechanisms promoting uterine smooth muscle growth in early pregnancy and/or labour.

Highlights

During pregnancy, myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and prepare for the onset of labour
nuclear factor of activated T-cell (NFAT) isoforms c1-c4 were expressed in P0 (n = 6) and passage 2 (P2) (n = 6) human myometrial cells, but NFATc1, NFATc2 and NFATc3 expression was suppressed in P0 and P2 human myometrial cells compared to myometrial tissue
NFATc2 expression was lower in P2 compared to P0 cells. (Fig. 1)

Summary

Introduction

Myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and prepare for the onset of labour. There is little understanding of how changes in calcium signalling in response to mechanical signals could drive changes in gene and protein expression in myometrium during early pregnancy or prior to labour to influence uterine development, growth and/or contractility. The link between exogenous signals such as mechanical stretch and endocrine signals and intracellular events to drive human uterine smooth muscle cell hyperplasia in early-mid pregnancy and hypertrophy in human myometrium are not clearly defined. In other cell types and smooth muscles, intracellular calcium signals are well known to regulate gene expression and growth through downstream activation and modulation of transcription factors [11,12,13,14] but in human pregnant myometrium, there is little documented about the role of Ca2+-sensitive transcription factors

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