Single-cell mechanics and calcium signalling in organotypic slices of human myometrium

Abstract

Elucidation of cellular mechanisms regulating myometrial contractility is crucial for improvement in management of many obstetric abnormalities, such as premature delivery, uterine dystocia and post-partum haemorrhage. Myometrial contractions are triggered by periodic synchronous rises in intracellular calcium concentration ([Ca2+]i) elicited by spontaneously generated action potentials propagating throughout the entire myometrium. During labour, hormones like oxytocin and prostaglandins potentiate uterine contractions by increasing their duration, strength and frequency. The most informative approach to studying the mechanisms underlying hormonal modulation of uterine contractility is to record [Ca2+]i responses to hormones in intact myometrial samples that have not been subjected to enzymatic treatment for cell isolation or cell culture conditions. However, the spatio-temporal resolution of such recording is limited due to the motion artifacts occurring in contracting tissue. Here we describe the application of our newly developed motion correction algorithm to investigate the [Ca2+]i dynamics in control and oxytocin stimulated slices of human myometrium on a cellular level. We present evidence that oxytocin induces asynchronous [Ca2+]i oscillations in individual myocytes within intact myometrium which are similar to those observed in cultured cells. The oscillations occur between synchronous action potential-driven [Ca2+]i transients but appear to be unrelated to contractions. Furthermore, the oxytocin-triggered [Ca2+]i oscillations wane within 30–50 min of hormone application, while the action potential induced [Ca2+]i transients remain augmented. We conclude that oxytocin-induced [Ca2+]i oscillations are not relevant to the acute regulation of myometrial contractility but may play a role in longer-term regulatory processes, for example, by triggering gene expression.

Calcium Signaling in Interstitial Cells: Focus on Telocytes

“…Oxytocin-induced [Ca 2+ ]i oscillations have been demonstrated in primary cultures of human uterine myocytes [ 98 , 99 ], but data recorded in intact cells residing within the myometrium are limited. However, a recent study on organotypic slices from human myometrium indicated that oxytocin-induced [Ca 2+ ]i oscillations occurred only in a proportion of cells and were not relevant for the acute regulation of myometrial contractility, but the authors suggested the involvement of [Ca 2+ ]i oscillations in long-term regulatory processes, e.g., gene expression triggering [ 100 ]. These cells were identified to be ICCs or ICLCs and described to be morphologically and phenotypically distinct by SMCs.…”

“…Modulation of TCs’ growth by mechanical factors via calcium channels has a degree of mechanical sensitivity [ 123 ] and correlates with the TCs’ ability to communicate through gap junctions [ 40 , 46 ], the calcium involvement in myometrium proliferation [ 154 , 155 ] and contraction [ 100 ]. Therefore, we propose the hypothesis that TCs contribute to smooth muscle growth in areas with high mechanical forces.…”

Seipin deficiency leads to defective parturition in mice†

“…Myometrial contraction is a prerequisite for natural parturition. It is mediated by elevated [Ca 2+ ] i [2][3][4]. Both SR Ca 2+ efflux [5,6] and extracellular Ca 2+ influx [7,8] in the myometrium.…”

“…It is known that the myometrium plays an essential role in regulating uterine quiescence and contraction, and progesterone and estrogen play important roles in regulating myometrium activities [1]. Similar as other muscle cell contractions, myometrial contractions are also mediated by elevated intracellular calcium concentration ([Ca 2+ ] i ), which is regulated by both Ca 2+ release from intracellular stores in the sarcoplasmic reticulum (SR) and Ca 2+ entry from the extracellular space [2][3][4]. Both SR Ca 2+ efflux [5,6] and extracellular Ca 2+ influx [7,8] in myometrial smooth muscle cells are important for myometrial contractions during pregnancy.…”

A new molecular risk pathway for postpartum mood disorders: clues from steroid sulfatase–deficient individuals

“…Additionally, compared to non-postpartum mice, lactating female mice show gene expression changes in the gonadotropes of the anterior pituitary gland in pathways relating to metal ion transport, cell adhesion, and positive regulation of cGMP metabolic processes (Qiao et al 2016). Finally, these physiological (Loftus et al 2015), immune system activation (Kimura et al 2006), and structural changes in the mammary gland, uterus, and ovaries (Thorne et al 2015). The ideas discussed above suggest a number of interrelated predictions.…”