mRNA expression and localization of bNOS, eNOS and iNOS in human cervix at preterm and term labour.
BACKGROUND
Preterm birth is the primary cause of the neonatal mortality and morbidity. There will be no preterm birth without a cervical softening. Nitric oxide (NO) is shown to be a mediator of term cervical ripening. The aim of this study was to investigate mRNA expression of the three isomers of NO synthases (NOS) and to identify them by immunohistochemistry in the human cervix at preterm birth compared to term.


METHODS
The three isomers of NOS--inducible (iNOS), endothelial (eNOS) and neuronal (bNOS)--were investigated in the human cervix. The expression of mRNA was determined using Real-Time Multiplex RT-PCR. The localisation of synthases in the cervical tissue was analysed using immunohistochemistry. Cervical biopsies were obtained from 4 groups of women without clinical signs of infection: preterm (PTL), term labour (TL), preterm not in labour (PTnotL) and term not in labour (TnotL) patients. One-Way ANOVA, Kruskal-Wallis, Student t-test or Mann-Whitney test were applied as appropriate to determine statistically significant differences among the groups.


RESULTS
Patients in preterm labour had significantly (p < 0.01) higher mRNA levels of all the three NOS isomers compared to those in term labour. Women not in labour, irrespective of gestational age, thus with unripe cervices, had significantly lower eNOS mRNA levels compared to those in labour (p < 0.01). Immunoreactivity for all three NO synthases was observed in each examined sample in all groups. The bNOS staining was the most prominent.


CONCLUSIONS
The mRNA levels were higher in the preterm labour group compared to the women at term labour. The significant increase of the eNOS mRNA expression, from the unripe to the favourable cervical state during labour, may indicate a role of eNOS and supports the role of NO in the cervical ripening process. All the three synthases were identified by immunohistochemistry in all the groups of study.
Törnblom
Susanne Abelin
SA
Division of Obstetrics and Gynaecology, Department of Woman and Child Health, Karolinska University Hospital, Karolinska Institute, 171 76 Stockholm, Sweden. Susanne.Abelin@kbh.ki.se
Maul
Holger
H
Klimaviciute
Aurelija
A
Garfield
Robert E
RE
Byström
Birgitta
B
Malmström
Anders
A
Ekman-Ordeberg
Gunvor
G
D002584:Cervix Uteri / Q000166:cytology / Q000201:enzymology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007743:Labor, Obstetric / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D007752:Obstetric Labor, Premature / Q000201:enzymology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism
D012333:RNA, Messenger; C496320:NOS1 protein, human; C496314:NOS3 protein, human; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III