Oral Virtual Presentation (Virtual only) ESA-SRB-ANZBMS 2021

Assessment of the tocolytic nifedipine in pre-clinical primary models of preterm birth (#114)

Bridget Arman 1 2 , Natalie Binder 1 2 , Natasha de Alwis 1 2 , Sally Beard 1 2 , Danielle Debruin 3 4 5 , Alan Hayes 3 4 5 , Stephen Tong 2 , Tu'uhevaha Kaitu'u-Lino 1 2 , Natalie Hannan 1 2
  1. Department of Obstetrics and Gynaecology, University of Melbourne, Heidelberg, Victoria, Australia
  2. Mercy Perinatal, Heidelberg, Victoria, Australia
  3. Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia
  4. Australian Institute for Musculoskeletal Science, Victoria University, St Albans, Victoria, Australia
  5. Department of Medicine - Western Health, Melbourne Medical School, University of Melbourne, St Albans, Victoria, Australia

Objective

Spontaneous preterm birth is the leading cause of perinatal morbidity and mortality, with ~15 million babies born preterm/year globally. Nifedipine, currently used clinically to delay preterm birth, has limited efficacy. Furthermore preclinical data on nifedipine’s mechanisms of actions are lacking. We hypothesise that nifedipine does not reduce the inflammation central to the pathophysiology of preterm myometrial contractions. We aimed to assess the anti-inflammatory and anti-contractile effects of nifedipine on myometrium using a novel pipeline encompassing in vitro, in vivo and ex vivo human and mouse models of preterm birth. 

Methods

Inflammatory cytokine gene expression was evaluated (qPCR) following treatment of the myometrial cell line PHM1-41 with tumour necrosis factor-α (TNFα;0.1ng/ml) and lipopolysaccharide (LPS;100ng/ml) ±nifedipine (10µM). Myometrial contraction assays (PHM1-41 cells embedded in collagen gel) assessed the anti-contractile efficacy of nifedipine on TNFα/LPS-induced contractions. Primary human myometrial tissue (non-labouring; collected at caesarean-section) was assessed ex vivo (DMT Myograph) to evaluate the effect of nifedipine on spontaneous myometrial contractions. A mouse model of LPS-induced preterm birth was developed to determine whether nifedipine delayed delivery and altered uteri expression of contraction-associated genes following birth.

Results

TNFα/LPS treatment significantly increased gene expression of pro-inflammatory cytokines interleukin (IL)-1B, IL-6 and CXCL8 in myometrial cells compared to control (n=5), and addition of nifedipine had no effect. Myometrial contraction assays demonstrated nifedipine treatment reduced TNFα/LPS-induced contractions to baseline levels (n=3). Nifedipine treatment potently diminished spontaneous myometrial contractions in human primary myometrial tissue assays compared to vehicle (ethanol) treatment (n=3). Preliminary in vivo findings revealed nifedipine delays LPS-induced preterm birth in 25% of mice.

Conclusion

Nifedipine reduced myometrial contractions in both human primary tissue and a cell line. Nifedipine partially prevented preterm birth in a mouse model. Given nifedipine did not reduce pro-inflammatory gene expression, we suggest nifedipine does not modulate inflammatory cytokines in the myometrium.