Preterm birth is the leading cause of neonatal morbidity and mortality in the developed country and its prevalence increased in the last years. Administration of progesterone in high risk women may reduce the risk of preterm birth. The aim of this study was to explore the effect of progesterone on the biomechanical properties of cervixes from rats injected with lipopolysaccharides (LPS) to create an inflammatory status.
Time-pregnant Sprague-Dawley rats were intraperitoneally injected with LPS (500 μg/kg), or an equivalent volume of vehicle, for 3, 6, 12, or 24 hours before laparotomy performed at 22 days of gestational age. Trachelectomy were performed and cervixes were equilibrated in isolated organ baths. This system was used as cervimeter, which stretches the cervical tissues in incremental steps of 0.74 mm at 10-minutes intervals. Biomechanical properties were analyzed in term of maximal amplitude, residual tension and contractions frequency of the cervix. Cervixes were randomly assigned into two groups, with or without progesterone pre-treatment in organ bath (100 μM for 30 min). Statistical analysis included Student′s t-test and p <0.05 were considered significant.
Mechanical responses from 15 cervixes were analyzed in this new model. The maximal amplitude (p<0.0001) and contractions frequency (p=0.19) were increased in the LPS group compared to the control group. Our data also showed differences in term of passive tension between cervixes exposed to LPS for 3 and 12 h (p<0.0001), the tension being higher in the 3 h group. In the LPS group, we didn′t observe any effect of progesterone in term of maximal amplitude (p=0.56) and residual tension (p=0.32) of the cervix.
Our data demonstrate that cervixes, from pregnant rat treated with LPS, display significant differences in their passive and active biomechanical properties. However, acute progesterone treatment didn′t modify the mechanical behavior of the cervix.
© 2008 Mosby, Inc. Published by Elsevier Inc. All rights reserved.