P-497 High-concentration of E2 post-controlled ovarian hyperstimulation promotes cervical extracellular matrix degradation by up-regulating UBA52
Authors: Bai S , Zhang J , Cao C , Chen H 
Published: June 2023

Abstract

Study question
To explore the effect of high concentration of E2 after controlled ovarian hyperstimulation (COH) on the extracellular matrix of cervical tissue in the second trimester.

Summary answer
The high concentration of E2 after COH promotes cervical ECM degradation leading to cervical insufficiency of pregnancy in ART by up-regulating UBA52.

What is known already
Assisted reproductive technology (ART) is a double-edged sword. While effectively solving infertility, ART also associated with many obstetric complications like preterm birth, although, the reason is currently unclear. Cervical insufficiency (CI) caused by degradation of extracellular matrix (ECM) is one of the most important causes of preterm birth. All patients undergoing ART need to receive controlled ovarian hyperstimulation (COH), leading to a sharp rise of the serum level of E2, which has a significant impact on the blood system, liver and kidney, but the effect on the cervix is unclear.

Study design, size, duration
1.Retrospectively analyzed the clinical data of our center to compare the incidence of cervical insufficiency between ART singleton pregnancy and natural singleton pregnancy. 2. Establishing a post-COH pregnancy mice model, to analyze how the concentration of E2 affect the cervical ECM.

Participants/materials, setting, methods
The incidence of CI and the serum level of E2 on the day of human chorionic gonadotropin (HCG) in ART singleton pregnancies and natural singleton pregnancies was compared. The pregnant mice models after COH were established to detect the serum level of E2 and to investigate the structure of the cervical ECM. We detected the overall expression level of collagen and selected the mark gene using RNA-seq.
Relevant biological experiments were used for verification 14/5000

Main results and the role of chance
The incidence of CI in ART singleton pregnancies was significantly higher than that in natural singleton pregnancies (7.80% vs. 3.54%, p&lt;0.0001) and so was the serum level of E2 in patients with CI during pregnancy than those without (3333 ± 1116.61 pg/ml, n = 40 vs. 2437 ± 1072.2 pg/ml, n = 9, p=0.034). Furthermore, the serum level of E2 was markedly higher in the COH pregnant mice models (175.68 ± 38.72 pg/ml, n = 10 vs. 235.43 ± 67.24 pg/ml, n = 11, p=0.024) and the expression of collagen was reduced significantly, and DEGs related to ECM organization pathway was significantly enriched. Our results indicated that matrix metalloproteinases (MMPs) should not be responsible for the collagen degradation in ECM of cervix. Interestingly, the ubiquitination level of type I collagen increased compared with the control group both in vitro and in vivo experiments. UBA52, a component of the ubiquitin-encoding gene, has been shown to strongly upregulated among these ubiquitination related genes (URGs), and its expression was demonstrated to be E2 concentration dependent. Also, an estrogen response element (ERE) was detected in UBA52 promoter region, and direct binding of ER to ERE was validated, implying that UBA52 might be a key regulator for collagen degradation.

Limitations, reasons for caution
Firstly, the findings of clinical data were still inevitably subject to retrospective study limitations. Secondly, we found that UBA52 may be the target gene that causes the increased ubiquitination of type I collagen in mouse cervical tissue after COH, but the deeper related mechanism was still unclear.

Wider implications of the findings
Our research provides evidence that a high concentration of E2 after COH is harmful to cervical function leading to cervical insufficiency, which further underlines the importance of providing special care to women who use ART for pregnancy.

Trial registration number
not applicable