Advanced glycation products' levels and mechanical properties of vaginal tissue in pregnancy

Weli, Homayemem K.; Akhtar, Riaz; Chang, Zhuo; Li, Wen-Wu; Cooper, Jason; Yang, Ying

Abstract

Objectives
Non-enzymatic glycation is closely associated with altered mechanical properties of connective tissue. Pregnancy, marked with high levels of female hormones, confers unique alteration to the mechanical properties of pelvic connective tissues in order to meet their physiological demands. However, there are few studies on glycation content and its influence on the mechanical properties of pelvic connective tissues during pregnancy. We hypothesise that the glycation content in pelvic tissues will change with a corresponding alteration in their mechanical properties, and that these changes are influenced by hormone levels. This study aims to investigate the correlation of vaginal tissue glycation content and mechanical property changes during pregnancy in association with the expression of a key pregnancy hormone (oestrogen) receptor, and an antioxidant enzyme, glyoxalase I.

Study design
A rat vaginal tissue model (tissues from non-pregnant and E15-E18 (last trimester) pregnant rats) was used in this study. Mechanical characteristics of vaginal tissues were analysed by a ball-indentation technique while modulus and morphology of the collagen fibrils within the tissues were measured with atomic force microscopy. A glycation marker, pentosidine, was quantified by a high performance liquid chromatography. The expression of oestrogen receptor and glyoxalase I in the tissue was qualified by immunochemical staining. The glycosaminoglycan (GAG) concentration difference in the tissues were quantified by a biochemical assay.

Results
Pregnant rat vaginal tissue was characterised by significantly lower amounts of pentosidine, higher oestrogen receptor and glyoxalase I expression with larger creep, lower elastic modulus, larger fibril diameter and higher GAG content than their non-pregnant counterpart. There was a negative correlation between pentosidine and vaginal tissue creep.

Conclusion
There was a reduction in vaginal tissue pentosidine in pregnancy with an associated increase in oestrogen receptor and glyoxalase I immunoexpression. Reduced glycation was associated with increased creeping of vaginal tissue. Oestrogen may therefore play a role in the increase of the vaginal wall’s capacity to stretch through glyoxalase I up-regulation and subsequent glycation reduction. The new insight of the correlation of women’s oestrogen level, glycation reaction and pelvic tissue mechanical property from this study may enhance our understanding of some pelvic organ diseases.

Citation

Weli, H. K., Akhtar, R., Chang, Z., Li, W., Cooper, J., & Yang, Y. (2017). Advanced glycation products' levels and mechanical properties of vaginal tissue in pregnancy. European Journal of Obstetrics and Gynecology and Reproductive Biology, 78-85. https://doi.org/10.1016/j.ejogrb.2017.04.037

• Acceptance Date: Apr 19, 2017
• Publication Date: Apr 23, 2017
• Journal: European Journal of Obstetrics and Gynecology and Reproductive Biology
• Print ISSN: 0301-2115
• Publisher: Elsevier
• Pages: 78-85
• DOI: https://doi.org/10.1016/j.ejogrb.2017.04.037
• Keywords: pregnancy; mechanics; oestrogen; glyoxalase I; advanced glycation products
• Publisher URL: https://doi.org/10.1016/j.ejogrb.2017.04.037