Is α2-macroglobulin important in female stress urinary incontinence?

Abstract

BACKGROUND: Loss of mechanical stability of the urethra and bladder is thought to be important in the development of stress urinary incontinence (SUI). The vaginal wall is the main supporting tissue for pelvic organs and changes in components of supporting tissues are known to be involved in the pathophysiology of SUI. METHODS: We evaluated changes in expression of α2-macroglobulin (α2-M), a protease inhibitor, in vaginal wall tissues from premenopausal women (aged 42-45 years) with SUI (n = 28) compared with menstrual cycle-matched continent women (controls, n = 29). The distribution of α2-M in vaginal wall tissues and fibroblasts was analysed by immunohistochemistry and immunofluorescence. Expression levels of α2-M mRNA and protein was determined by relative real-time quantitative PCR and enzyme-linked immunosorbent assay, respectively. Protease inhibition was measured to assess bioactivity. RESULTS: Vaginal wall tissues do express α2-M. Expression of α2-M mRNA and protein was significantly higher in tissues from controls compared to women with SUI in both proliferative and secretory phases (P < 0.05). Protease inhibitory activity of α2-M was significantly higher in tissues from controls compared to women with SUI in the secretory phase (P < 0.05), but we found no difference in the proliferative phase between groups. α2-M protein level was lower in the proliferative phase than the secretory phase in both controls and SUI patients, while for α2-M mRNA this was found only in controls. CONCLUSIONS: Decreased expression of α2-M mRNA and protein and protease inhibitory activity in the vaginal wall tissues of women with SUI may contribute to the development of SUI. © The Author 2007. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.