Procollagen Aminoterminal Propeptide Type I in Endometriosis

Abstract

Fibrosis is frequent in endometriotic lesions; procollagen aminoterminal propeptide type I (PINP) is a degradation product of collagen synthesis. This study aims to measure the levels of PINP in peritoneal fluid (PF) and plasma (PL) of women with and without endometriosis, in order to evaluate whether they correlate with the severity of the disease. Cross-sectional study. PF and PL samples were obtained from 93 women with endometriosis and 68 controls (infertility, n=16; uterine myomas, n=25; ovarian cyst, n=21; pelvic pain, n=5; tubal sterilization, n=1). Only patients of reproductive age were included in the study; none of the subjects had used hormonal therapies in the 6 months before surgery. The extent of endometriosis was scored using the revised American Fertility Society (rAFS) classification. The phase of the cycle was determined according to the menstrual history and progesterone levels. The serum concentration of PINP was measured by a sandwich enzyme-linked immunosorbent assay utilizing purified alpha 1-chain specific rabbit antibodies. PINP concentration was not normally distributed as determined by the Shapiro-Wilks test; therefore, the Mann-Whitney U test was used to compare its concentration between the two groups. The relationship between PL and PF PINP concentration was evaluated by the non-parametric Spearman correlation coefficient. No significant difference was observed in the mean age of patients in the two groups. PINP concentration was significantly higher in PF in women with severe endometriosis (rAFS stage III-IV, mean ± SEM, 1067.2±198.4 ng/mL) than in mild endometriosis (rAFS stage I-II, 266.5±59.7 ng/mL) (p<0.001) and in controls subjects (p=0.015). PINP concentration was significantly higher in the PF than in PL both in women with endometriosis (p<0.001) and in controls (p<0.001). No significant correlation was observed between PL and PF PINP concentration both in women with endometriosis (p=0.780) and in controls (p=0.970). No significant change in PINP PF and PL levels was observed during the menstrual cycle. By contrast, no significant difference (p=0.328) was observed in the PINP PF concentration between all women with endometriosis (780.4±137.0 ng/mL) and controls (526.5±135.1 ng/mL). No significant difference (p=0.967) was observed in PINP PL concentration between women with endometriosis (47.5±2.5 ng/mL) and controls (50.0±2.9 ng/mL). Similarly, no significant difference was observed in PL PINP concentration between women with mild (42.0±4.7 ng/mL) and severe endometriosis (49.5±3.0 ng/mL). PF PINP levels are significantly higher than PL levels both in women with and without endometriosis. Women with severe endometriosis have higher PINP PF levels than subjects with mild endometriosis and controls, these observations being in accord with previous studies showing that PINP levels are associated with increased fibroblast activity.