Metabolic Changes Of Collagen Type Ⅰ&Ⅲ Of Anterior Vaginal Tissue In Women With Pelvic Organ Prolapse

OBJECTIVE: The aim is to investigate the content of type I &III collagen and their synthesis and degradation products including carboxyterminal propeptide of type I procollagen (PICP), carboxyterminal telopeptide of type I collagen (ICTP) and aminotermimal propeptide of type III procollagen (PIIINP) in anterior wall of vaginal tissue, and to explore whether the metabolic changes in anterior vaginal tissue could contribute to the etiology of pelvic organ prolapse(POP).METHODS: Transvaginal biopsies were obtained from anterior vaginal tissue in premenopausal and postmenopausal patients with POP and comparable premenopausal and postmenopausal control groups during transvaginal operations. Sixty-three women participated in the study. They were divided into 4 groups as follows: 16premenopausal patients with POP (group 1), 19 premenopausal patients with neither UI(urinary incontinence) nor POP (group 2), 18 postmenopausal patients with POP(group 3), 10 postmenopausal patients with neither UI nor POP (group 4).The concentration of type I & III collagen, PICP, ICTP and PIIINP in specimen were biochemically detected by enzyme linked immunosorbent assay (ELISA commercial kits), followed by tissue specimen homogenization. RESULTS: The content of type I collagen in premenopausal POP group and postmenopausal POP group are significantly lower than that in the control groups(-21.28% and -24.06%, respectively). The content of ICTP reduced significantly both in premenopausal POP group and in postmenopausal POP group. High relativity was found in the variability of type I collagen and ICTP, the correlation coefficient of them was -0.876 (P<0.05) of the premenopausal groups and -0.842 (P<0.05) of the postmenopausal groups. Compared to premenopausal controls and postmenopausal control group, the mean' concentration of PICP was higher in POP groups, premenopausal or postmenopausal, but the difference between them was not statistically significant (P>0.05).There was significant difference in the level of type III collagen between the POP groups and control groups whether in premenopausal patients or in postmenopausal patients(-29.70% and -29.18%, respectively, P<0.05). Compared to the control groups, the concentration of PIIINP was also significantly lower in POP patients, whether in premenopausal group or postmenopausal group. Significant positive correlation was found between type III collagen and PIIINP (premenopausal groups: r =0.732 ; postmenopausal groups: r =0.713 ).Significant differences of premenopausal groups' content of type I collagen , type III collagen and ICTP were found only between slight stage and gravis stage(P<0.05), while among the postmenopausal groups the content of I collagen , type III collagen , ICTP and PIIINP were found significances between slight stage and between gravis stage(P<0.05). No significant difference was found in varies stages of PICP, whether in premenopausal or in postmenopausal groups(P>0.05).As to age, parity and menopausal time, we found that postmenopausal POP patients (group 3) had significantly older age when compared to premenopausal patients with POP(groupl). CONCLUSION: The content of type I &IIIcollagen in anterior vaginal tissue are significantly lower in premenopausal and postmenopausal women with POP, while the expression of ICTP significantly elevated and PIIINP significantly reduced. We also found a strong correlation between the quantity of type I collagen and ICTP, and between type III collagen and PIIINP in anterior vaginal tissue, suggesting that collagen metabolism altered in pelvic organ prolapse patients. Increased degradation of type I collagen and less synthesis of type III collagen should result in a decreased concentration of collagen, a less flexible form of extracellular matrix, also suggesting a connective tissue with impaired mechanical function. Those tissues probably were less elastic and less strong, more likely to be broken, which suggested that the degeneration of biomechanical properties in pelvic support construction might lead to the occurrence of POP.As to different stage of POP, slight stage and gravis stage had much more significant differences, which suggested that the slight stage maybe the best curable opportunity, especially for the conservative therapy.Also, we found that postmenopausal patients with POP (group 3) had significantly older age and much longer postmenopausal time, when compared to premenopausal patients in group 1. Basing on these investigations, we could reached the conclusion that the collagen metabolism in anterior vaginal tissue in postmenopausal patients with POP might be modulated by aging process and reproductive hormones, which suggested that age and the level of estrogen might be involved in the pathogenesis of POP postmenopausally.