Whole blood RNA sequencing reveals a differential transcriptomic profile associated with cervical insufficiency: a pilot study

BACKGROUND

The uterine cervix is a mechanical and immunological barrier against ascending infection during pregnancy. Cervical insufficiency (CI), a painless cervical dilation that occurs in the mid-trimester, is an important cause of extremely preterm birth. We hypothesized that women with CI have a differential transcriptomic profile. Therefore, we compared the transcriptomic profile of peripheral blood in women with CI and that of controls.

METHODS

RNA sequencing was used to generate the global gene expression profiles of 11 women with CI and 4 controls, and differential expression analysis was performed to identify genes showing significant expression changes between the CI (n = 11) and control (n = 4) groups as well as between the CI-preterm (n = 7) and CI-term (n = 4) groups. Gene set enrichment was assessed in terms of Gene Ontology processes, and a subset of differentially expressed genes in CI was validated in a different sample-set by qRT-PCR and ELISA.

RESULTS

Thirty genes were differentially expressed between the CI and control groups. Differentially upregulated genes in the CI group included neutrophil-mediated immunity-associated (DEFA3 and ELANE) and bicarbonate transport-related genes. The serum concentration of alpha defensin 3 was significantly higher in women with CI than in controls (P = 0.014). Analysis of differential gene expression according to pregnancy outcomes revealed 338 differentially expressed genes between the CI-term and CI-preterm groups. Immune and defense response to organism-associated genes and influenza A and NOD-like receptor signaling pathways were upregulated in the CI-term group.

CONCLUSIONS

Our results revealed significant differences in the whole blood transcriptomic profiles of women with CI compared to those of controls. Different immune responses in women with CI may affect pregnancy outcomes.

Cervical collagen and biomechanical strength in non-pregnant women with a history of cervical insufficiency

BACKGROUND

It has been suggested that cervical insufficiency (CI) is characterized by a "muscular cervix" with low collagen and high smooth muscle concentrations also in the non-pregnant state. Therefore, the aim of this study was to investigate the biomechanical properties, collagen concentration, smooth muscle cell density, and collagen fiber orientation in cervical biopsies from non-pregnant women with a history of CI.

METHODS

Cervical punch biopsies (2 x 15 mm) were obtained from 57 normal non-pregnant women and 22 women with a history of CI. Biomechanical tensile testing was performed, and collagen content was determined by hydroxyproline quantification. Histomorphometry was used to determine the volume densities of extracellular matrix and smooth muscle cells from the distal to the proximal part of each sample. Smooth muscle cells were identified using immunohistochemistry. Finally, collagen fiber orientation was investigated. Data are given as mean +/- SD.

RESULTS

Collagen concentration was lower in the CI group (58.6 +/- 8.8%) compared with the control group (62.2 +/- 6.6%) (p = 0.033). However, when data were adjusted for age and parity, no difference in collagen concentration was found between the two groups. Maximum load of the specimens did not differ between the groups (p = 0.78). The tensile strength of cervical collagen, i.e. maximum load normalized per unit collagen (mg of collagen per mm of specimen length), was increased in the CI group compared with controls (p = 0.033). No differences in the volume density of extracellular matrix or smooth muscle cells were found between the two groups. Fibers not oriented in the plane of sectioning were increased in CI patients compared with controls.

CONCLUSIONS

Cervical insufficiency does not appear to be associated with a constitutionally low collagen concentration or collagen of inferior mechanical quality. Furthermore, the hypothesis that a "muscular cervix" with an abundance of smooth muscle cells contributes to the development of cervical insufficiency is not supported by the present study.

[Levels of fetal and plasma fibronectin in patients with cervical incompetence]

In 45 gravidae (below 24 weeks) fetal fibronectin (fF) was measured in cervico-vaginal discharge and plasma fibronectin (pF) was evaluated in venous blood. Twenty women had cervical incompetence (CI) diagnosed and 25 healthy gravidae served as a control. The fF level in patients with CI (0.073 +/- 0.014 mg/ml) was significantly (p < 0.01) higher than that found in the control group (0.058 +/- 0.011 mg/ml). The same was true for pF (p < 0.001). A diagnostic value of fibronectin levels in patients suspected of cervical incompetence is suggested.

Cervical collagen in non-pregnant women with previous cervical incompetence

OBJECTIVE

To study the cervical collagen in non-pregnant women with a history of congenital cervical incompetence.

SUBJECTS

Ten non-pregnant women with congenital cervical incompetence, defined as cervical incompetence in the first pregnancy in a woman without previous cervical trauma. Seventy-one normal non-pregnant women (31 nulligravidae, nine nulliparous and 31 parous women) served as controls.

METHOD

Cervical biopsies were analysed for the hydroxyproline concentration and extractability to express the concentration and the stability of the collagen.

RESULTS

Women with cervical incompetence had markedly lower median cervical hydroxyproline concentration when compared to normal parous women (11.1 (range 6.11-18.5) micrograms/mg wet weight vs. 16.9 (range 7.7-29.8) micrograms/mg wet weight; P = 0.003, Mann Whitney test) and the extractability was almost twice the value found in normal parous women (80.2% vs. 49.5%; P = 0.03, Mann Whitney test). Both pregnancy per ce and parturition caused a significant decrease in the hydroxyproline concentration when compared to values found in nulligravidae (P < 0.0001, Kruskall Wallis test).

CONCLUSIONS

Congenital cervical incompetence seems associated with a low collagen concentration in the cervical connective tissue in the non-pregnant state.

Connective tissue changes in the cervix during normal pregnancy and pregnancy complicated by cervical incompetence

When postpartum cervical biopsy specimens were compared with biopsy specimens from nonpregnant women, they revealed a 12-fold decrease in mechanical strength, a 50% reduction in the concentrations of collagen and sulfated glycosaminoglycans, a 35% reduction in hyaluronic acid, an increase in collagen extractability, and a fivefold increase in collagenolytic activity. Primiparas with relatively high concentrations of collagen and hyaluronic acid had relatively long cervical dilatation times during established labor, suggesting a physiologic importance to these variables. This correlation was not found in multiparas, even though the mean values of the biochemical parameters tested were similar to those in primiparas. Second-trimester biopsy specimens taken from patients with cervical incompetence contained normal collagen concentrations, but relatively high collagen extractabilities and collagenolytic activities, exceeding normal postpartum values. A biopsy specimen that was tested biomechanically had a very low strength and very high extensibility. Most likely, these data reflect a high turnover of collagen in incompetent cervices, resulting in a high proportion of newly synthesized collagen with low biomechanical strength.

Decreased elastic fibers and desmosine content in incompetent cervix

Incompetence of the uterine cervix is a syndrome of painless, progressive dilatation and effacement occurring between the sixteenth and twenty-fourth weeks of gestation that represents abnormal functioning. It may serve as a model to elucidate normal function. Because the incompetent cervix results in painless opening of this organ without uterine contraction before term gestation, it is considered one of the causes of midtrimester spontaneous abortion, habitual spontaneous abortion, and early preterm labor. Untreated, it leads to rapid expulsion and often death of the fetus. We used light microscopy to compare decreased elastic fibers in incompetent cervices with those of normal nonpregnant and pregnant cervices. Morphologic analysis of this difference was extended to biochemical quantification of elastin content in one patient with cervical incompetence. The decrease in elastin suggests that one function of cervical elastin may be to maintain a closed and undilated cervix throughout gestation. There may be a relationship between changes in cross-linked elastin and the incompetent cervix; further studies are therefore indicated.