Differential expression of smooth muscle regulatory proteins in the uterosacral ligaments of women with uterine prolapse

Proteomic Analysis of the Uterosacral Ligament in Postmenopausal Women with and without Pelvic Organ Prolapse

BACKGROUND

Pelvic organ prolapse (POP) is a major health problem in adult women that involves many factors. No proteomic analysis has been conducted exclusively in POP patients. This study aimed to identify the differential expression of proteins that may be involved in POP by proteomic analysis.

METHODS

Samples of the uterosacral ligament (USL) were collected from five POP patients and five non-POP patients matched according to age, parity, and menopausal status and analyzed using two-dimensional electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the mRNA expression of proteins that showed differential expression in the proteomic analyses.

RESULTS

Proteins differentially expressed between POP and non-POP patients were detected. Eight proteins that were down-regulated in the POP group were identified by MALDI-TOF-MS. These proteins included electron transfer flavoprotein, apolipoprotein A-I, actin, transgelin, cofilin-1, cyclophilin A, myosin, and galectin-1, and their expression was verified by qRT-PCR.

CONCLUSION

Using comparative proteomics, we identified eight differentially expressed proteins (including four cytoskeleton proteins and three proteins related to apoptosis) in the USL that may be involved in apoptosis associated with the tissue effects in POP pathophysiology.

Effect of estrogen on molecular and functional characteristics of the rodent vaginal muscularis

INTRODUCTION

Vaginal atrophy is a consequence of menopause; however, little is known concerning the effect of a decrease in systemic estrogen on vaginal smooth muscle structure and function. As the incidence of pelvic floor disorders increases with age, it is important to determine if estrogen regulates the molecular composition and contractility of the vaginal muscularis.

AIM

The goal of this study was to determine the effect of estrogen on molecular and functional characteristics of the vaginal muscularis utilizing a rodent model of surgical menopause.

METHODS

Three- to 4-month old Sprague-Dawley rats underwent sham laparotomy (Sham, N = 18) or ovariectomy (Ovx, N = 39). Two weeks following surgery, animals received a subcutaneous osmotic pump containing vehicle (Sham, Ovx) or 17β-estradiol (Ovx). Animals were euthanized 1 week later, and the proximal vagina was collected for analysis of contractile protein expression and in vitro studies of contractility. Measurements were analyzed using a one-way analysis of variance followed by Tukey's post hoc analysis (α = 0.05).

MAIN OUTCOME MEASURES

Protein and mRNA transcript expression levels of contractile proteins, in vitro measurements of vaginal contractility.

RESULTS

Ovariectomy decreased the expression of carboxyl-terminal myosin heavy chain isoform (SM1) and h-caldesmon and reduced the amplitude of contraction of the vaginal muscularis in response to KCl. Estradiol replacement reversed these changes. No differences were detected in the % vaginal muscularis, mRNA transcript expression of amino-terminal MHC isoforms, l-caldesmon expression, and maximal velocity of shortening.

CONCLUSION

Systemic estrogen replacement restores functional and molecular characteristics of the vaginal muscularis of ovariectomized rats. Our results indicate that menopause is associated with changes in the vaginal muscularis, which may contribute to the increased incidence of pelvic floor disorders with age.

TGF-beta 1 is a potential regulator of vaginal tropoelastin production

INTRODUCTION AND HYPOTHESIS

Our aims were to correlate transforming growth factor (TGF)-β1 and elastin mRNA expression in the vagina of women and to measure the effects of TGF-β1 on vaginal smooth muscle cell (SMC) proliferation and tropoelastin production.

METHODS

Vaginal walls were sampled in women (n = 20). TGF-β1 and elastin mRNA expression was assessed by RT-PCR. SMC cultures were performed from vaginal wall biopsies. SMC were incubated with TGF-β1, and cell proliferation was assessed by MTT-assay. Tropoelastin production was measured by the Fastin Elastin Assay.

RESULTS

There was a significant positive correlation between TGF-β1 and elastin mRNA (r = 0.784, P < 0.01). SMC proliferation was significantly increased by 10 ng/mL TGF-β1 [relative cell number, mean ± SD, 198% ± 32% of control (P = 0.01)]. Tropoelastin production was significantly increased by TGF-β1 [mean ± SD, 645% ± 180% of control (P = 0.01)].

CONCLUSIONS

There is a positive correlation between TGF-β1 and elastin mRNA expression in the vaginal wall. In vitro, TGF-β1 increases vaginal tropoelastin production in vaginal SMC.

The calpain system as a potential target for pelvic muscle reinforcement

The fascial and muscular components within the pelvic floor create a support mechanism that facilitates storage and voiding of urine. Their constituents are mainly fibrillar collagens I and III, which are responsible for maintaining tensile strength. Stretching and recoiling is enabled by the elastic fibers consisting of elastin on a scaffold of microfibrils, fibrillin-1 and -2. Calpains are intracellular Ca2+ -dependent cysteine proteases found in almost all eukaryotes and some bacteria. Calpains display limited proteolytic activity at neutral pH, proteolyzing substrates to transform and modulate their structures and activities, and are therefore called “modulator proteases”. By making selective limited proteolytic cleavages, they modulate the activity of enzymes, including key signaling molecules, and induce specific cytoskeletal rearrangements, accounting for their roles in signal transduction and structural stabilization. Understanding these mechanisms should provide avenues for novel therapeutic strategies to treat pathological processes such as urinary incontinence and pelvic prolapse.