Bhunia, Sudeshna (2021) Investigation of correlation of biochemical marker expression and mechanical properties of preterm membranes. Doctoral thesis, Keele University.

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Abstract

The fetal membrane surrounds and supports the developing fetus during the pregnancy. The cellular structure of the fetal membrane and the proteins synthesized by the cells of amniotic and chorionic membranes, maintain the mechanical integrity of the tissue membrane. Rupture of the fetal membrane is a fundamental stage in normal term delivery. However, preterm premature rupture of membranes (PPROM) leads to preterm birth, which remains a major concern worldwide as the largest contributor of perinatal and neonatal mortality and morbidity. The underlying mechanism of PPROM is complicated and requires further investigation. The aim of this project is to newly reveal the underlying mechanisms of PPROM through the study of mechanical and biochemical properties of fetal membranes in both full term and preterm via new experimental protocols. With ethical approval, 42 fetal membranes were collected for this study from women who had full term normal vaginal delivery, preterm (less than 37 weeks) vaginal delivery (PPROM), full term and preterm delivery via caesarean sections. Mechanical characterisation was conducted for fetal membrane from full term and PPROM normal vaginal deliveries. Two new mechanical test techniques were established. Ball indentation test and Optical Coherence Elastography, were applied for the first time to study fetal membrane comprehensively in ruptured, non-ruptured areas and at different sublayers using optical coherence tomography for the thickness study. Biochemical assays; histological and immunological staining, plus Western Blotting were performed to study the microstructural and biochemical molecular (Collagen, sGAG, MMP 9 and 13, fibronectin, IL-1β & progesterone receptors) changes on the same categories of samples. Furthermore, this study investigated the changing biochemical molecule expression levels of the membranes in response to the applied external mechanical stimulation and maternal risk factors (smoking and maternal hypoglycaemia). In addition, mechanotransduction signalling molecules (such as, nifedipine) and anti-inflammatory agent (dexamethasone) response was also studied in a new biomimetic experimental set up which was designed and implemented in full term and preterm fetal membranes from caesarean section deliveries. The mechanical test results revealed new evidence of noticeable difference between full term and preterm membranes. Preterm membranes showed great heterogeneity between ruptured and non-ruptured sites (creep property: 36%, modulus: 55%, thickness: 48%, collagen content: 59%, sGAG: 48%, and MMP 9: 57%) in comparison to their full term counterparts (creep property: 15%, modulus: 33%, thickness: 23%, collagen content: 24%, sGAG: 27% and MMP9: 23%). For the first time, a clear correlation between biomechanical and biochemical relations in full term and preterm was drawn. The in vitro loading model for the study of biochemical behaviours of fetal membrane in the presence of external force implied that cyclic force, either from fetal movement or fetal fluid can accelerate the synthesis of matrix degradation enzymes (MMPs) or trigger inflammation marker expression, leading to the weakening of the membranes. Preterm membrane was more sensitive to the force and biochemical environment than full term membrane, which might lead to premature rupture accidently. Downregulation of these biomarkers’ expressions by addition of nifedipine during culture suggested that the calcium signalling pathway may play an important role in mechanotransduction in fetal membrane cells. In addition, maternal smoking correlated with membrane weakness; however, diabetes did not show any direct correlation with it under the influence of external force in the current experimental model. Finally, the addition of dexamethasone in the cyclic loading environment decreased expressions of membrane weakening biomarkers, which reinstated dexamethasone’s beneficial effects on the prevention of fetal membrane rupture.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QD Chemistry > QD415 Biochemistry
Divisions: Faculty of Medicine and Health Sciences > School of Pharmacy and Bioengineering
Contributors: Yang, Y (Thesis advisor)
O'Brien, Shaughn (Thesis advisor)
Wu, P (Thesis advisor)
Depositing User: Lisa Bailey
Date Deposited: 24 Mar 2021 09:44
Last Modified: 24 Mar 2021 09:44
URI: https://eprints.keele.ac.uk/id/eprint/9296

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