Expression of scaffolding, signalling and contractile-filament proteins in human myometria: effects of pregnancy and labour

Abstract

Successful parturition requires the co‐ordination of numerous myometrial signalling events to allow for timely and efficient uterine contractions. Late pregnancy and labour onset in humans may be associated with changes in the expression of myometrial proteins implicated in such uterine contractile signal integration. Accordingly, in myometria from non‐pregnant women and pregnant women, not in labour or in labour, we examined the content of putative plasmalemmal scaffolding proteins (caveolin‐1 and ‐2) and compared these to the proportions of signal transducing rho‐associated kinases (ROK α and β) and contractile filament‐associated proteins α‐actin, myosin regulatory light chain (MLC20) and h‐caldesmon. There was no effect of pregnancy or labour on the proportion of caveolin, ROK β or α‐actin. However, pregnancy was associated with a decrease in ROK α and MLC20 such that ROK α: α‐actin and MLC20: α‐actin ratios were reduced compared to myometria of non‐pregnant women. In contrast, h‐caldesmon was up‐regulated in pregnancy resulting in an elevated h‐caldesmon: α ‐actin ratio. There were, however, no further significant changes in ROK α, MLC20 or h‐caldesmon expression with spontaneous or oxytocin‐induced labour. These data suggest that the mechanism(s) integrating myometrial signalling events with the onset of human labour does not involve differential alterations of the cellular expressions of caveolins, ROK, α ‐actin, MLC20 or h‐caldesmon.

Secreted surfactant protein A from fetal membranes induces stress fibers in cultured human myometrial cells

“…In line with this proposal, we first confirmed our previous data indicating that human cultured myometrial cells expressed functional binding sites and respond to purified SP-A to induce stress fiber formation via a pathway involving Rho-kinase (11). In human myometrium, Rho-kinase inhibition has been associated with reduction of uterotonic-induced myometrial contractions (9,12,35). We confirmed that pharmacological inhibition of Rho-kinase resulted in a clear reduction of stress fiber formation induced by SP-A.…”

<i>In vivo</i> and <i>in vitro</i> effects of <i>Bidens pilosa</i> l. (asteraceae) leaf aqueous and ethanol extracts on primed-oestrogenized rat uterine muscle.

“…Estrogens are steroid hormones with important functions in the regulation of specific sexual processes in females; they affect the myometrium at the end of the pregnancy by decreasing cellular membrane potential which increases the excitability of the uterus (Kurowicka et al, 2005;Riley et al, 2005) and then intervene in the initiation of labour during child birth. In addition, uterotrophic substances such as oxytocin, a neurohypophysial hormone, are frequently used to enhance myometrial contractile activity during labour (Lopez Bernal, 2003), and it is known that the physiological regulation of the oxytocin system is strongly steroid-dependent (Gimpl and Fahrenholz, 2001).…”

Gene and protein expression in the myometrium in pregnancy and labor

“…Whatever it may be, genomic studies constitute a necessary first step of orientation which should lead to a more elaborate hierarchical vision of the physiological mechanisms of gestation, in particular by establishing new links between the generic signaling pathways that are activated during normal or pathological gestation. Genomic studies also represent an indicative step that will need to be correlated with a systematic proteomic analysis of the myometrium (Riley et al 2005a, Riley et al 2005b. The latter will undoubtedly develop in the very near future.…”