Stretching of fetal membranes increases the concentration of interleukin-8 and collagenase activity,☆☆,

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Abstract

OBJECTIVE: The aim of this study was to determine whether stretching of fetal membranes can increase interleukin-8 concentration and collagenase activity. STUDY DESIGN: Strips of whole fetal membranes, amnion, or muscles of the lower uterine segment were stretched for 2 or 4 hours. Interleukin-8 and collagenase activity were measured in homogenized control and stretched samples. Immunohistochemical staining for interleukin-8 was carried out. RESULTS: The interleukin-8 concentration increased significantly after the whole fetal membranes were stretched for 2 and 4 hours (p < 0.0007 and 0.001, respectively). Also, stretching of amnion and muscles of the lower uterine segment for 2 and 4 hours increased the concentration of interleukin-8 significantly (p < 0 .0007 after 2 and 4 hours, respectively). Collagenase activity was significantly increased after stretching of amnion, amniochorion, and muscles of the lower uterine segment for 4 hours (p < 0.0007, 0.006, and 0.0007, respectively). After stretching, samples were darkly stained for interleukin-8 compared with control nonstretched samples. CONCLUSION: Stretching of amnion, amniochorion, and muscles of the lower uterine segment increased interleukin-8 production and collagenase activity. (Am J Obstet Gynecol 1996;174:843-9.)

Section snippets

MATERIAL AND METHODS

This research was approved by the research committee of Hamamatsu University. Written consent was obtained from all patients involved in this study.

A muscle biopsy specimen was collected from the lower uterine segment during elective cesarean sections and before any clinical signs of labor (n = 15). Cesarean sections were done because of previous cesarean sections (n = 10) or primigravid women with breech presentations (n = 5). All cases were between 38 and 40 weeks' of gestation. Multiple

RESULTS

Amnion, whole fetal membranes, and muscle strips from the lower uterine segment increased in length in response to stretching for 4 hours. Fig. 2 shows the percent increase in length of stretched biopsy specimens in response to traction in grams. Amnion has a remarkable ability for stretching, compared with whole fetal membranes.

. Percentage of increase in length of amnion, amniochorion, and uterine muscles in relation to traction in grams.

High concentrations of IL-8 were found in control whole

COMMENT

Fetal membranes do not line the uterine cavity passively, but they are in a state of continuous stretching and tension during pregnancy. The maximum stretching and tension are reached at term, and more stretching will occur with the start of uterine contractions.3 It was found that amnion can be stretched more than the whole fetal membranes. This observation is similar to normal cervical dilatation where the chorion, usually torn earlier, and the amnion will form the bag of forewater.

Mechanical

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    From the Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine.

    ☆☆

    Reprint requests: Emad El Maradny, Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine, 3600 Handa-cho, 431-31 Hamamatsu, Japan.

    0002-9378/96 $5.00 + 0 6/1/68535

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