Proceedings of The Physiological Society

University of Oxford (2011) Proc Physiol Soc 23, C57

Oral Communications

Distinct responses to prostaglandin E2 (PGE2) by human myometrial smooth muscle cells isolated from the upper and lower segment of the pregnant human uterus

A. A. Mosher1, R. M. Tribe3, S. Wood2, D. M. Slater1,2

1. Physiology & Pharmacology, University of Calgary, Calgary, Alberta, Canada. 2. Obstetrics & Gynaecology, University of Calgary, Calgary, Alberta, Canada. 3. St Thomas' Hospital, Kings College, London, United Kingdom.

A better understanding of the molecular pathways involved in the onset and maintenance of human labour could lead to improved management of preterm labour. Prostaglandins have long been implicated to play a role and our research has focused on the regulation of prostaglandin (PG) pathway in the uterus during pregnancy. Our overall hypothesis is the differential regulation of PG synthesis and PG receptors are important for maintaining the balance of myometrial quiescence throughout pregnancy and contractility during labour. We have demonstrated PGE2 can repress inflammatory chemokine output from primary human myometrial smooth muscle (MSM) cells isolated from lower segment of the uterus. This effect is mediated via EP2 and EP4, but not EP1 or EP3. As it has been suggested that there may be functional differences between upper and lower regions of the pregnant uterus, we wanted to investigate whether PGE2 would elicit the same effect in upper segment MSM cells. We hypothesize that MSM cells isolated from distinct uterine sites (upper versus lower segment) are capable of producing unique responses. Methods: Paired upper and lower segment myometrial biopsies were obtained from Caesarean section procedures at term, prior to labour onset and utilised to isolate RNA (n=12) or MSM cells (n=3). MSM cells were cultured to confluence and incubated over-night in serum free medium prior to treatment, with PG receptor agonists (10uM - 300pM) in the presence or absence of IL-1β (1ng/ml). Elaboration of interleukin-8 into the culture medium was assessed by ELISA. Results: Robust increases in IL-8 release by MSM cells from both the upper and lower segment of the pregnant uterus was observed following treatment with IL-1β compared to non-stimulated controls. In the lower segment MSM cells PGE2 significantly repressed IL-1β induced IL-8 output in a dose-dependent manner (Student’s t test, p*<0.05 at 30nM); however, this PGE2-mediated repression was not observed in upper segment HMSM cells. Furthermore, selective EP2 and EP4 agonists repressed IL-1β-induced IL-8 output in lower segment HMSM cells but failed to do so in upper segment HMSM cells. In addition, a prostacyclin receptor agonist elicited repression of IL-8 in lower segment but not upper segment HMSM cells. Conclusions: We demonstrate that within the uterus, smooth muscle cells isolated from two distinct uterine sites are capable of producing unique responses. We intend to further characterize these cells in order to use them as a model to study different regions of the uterus and improve our understanding of PG signalling within the pregnant human uterus.

Where applicable, experiments conform with Society ethical requirements