Relationship between the expressions of mitofusin-2 and procollagen in uterosacral ligament fibroblasts of postmenopausal patients with pelvic organ prolapse

Is there an association between pelvic organ prolapse and oxidative stress? A systematic review

Introduction and hypothesis

The pathophysiology of pelvic organ prolapse (POP) has not been fully elucidated, although accumulating evidence suggests that oxidative stress is involved. The present systematic review comprehensively discusses this topic.

Methods

The PubMed/Medline, Scopus, and Web of Science databases were searched for relevant studies published up to May 2021. This systematic review was registered in the PROSPERO database (registration number CRD42021242240). Two independent researchers screened and selected articles that fulfilled predefined inclusion criteria, performed a quality assessment, and extracted the relevant data. Of 901 original articles retrieved, 8 fulfilled the selection criteria and were included in the review.

Results

Elevated levels of markers of oxidative stress, such as advanced glycation end products, hydroxynonenal and hydroxydeoxyguanosine, were found in various parts of the pelvic floor of patients with POP. Accordingly, the levels of glutathione peroxidase and superoxide dismutase, known as major antioxidant enzymes, were reduced, compared to those in healthy controls. Levels of two other markers (mitofusin 2 and nuclear factor erythroid derived 2) also support hypotheses suggesting the involvement of oxidative stress in POP.

Conclusions

In the literature available, an association between oxidative stress and pelvic organ prolapse was confirmed.

Treatment of Pelvic Organ Prolapse by the Downregulation of the Expression of Mitofusin 2 in Uterosacral Ligament Tissue via Mesenchymal Stem Cells

Background: The relationship between pelvic organ prolapse (POP), an aging-related disease, and the senescence-related protein mitofusin 2 (Mfn2) has rarely been studied. The aim of the present study was to explore the therapeutic effects of the downregulation of Mfn2 expression by stem cells on POP through animal experiments. Methods: First, a rat POP model was constructed by ovariectomy and traction. The rats in the non-pelvic organ prolapse (NPOP) and POP groups were divided into four groups for negative controls (N1−N4, N1: NPOP-normal saline; N2: NPOP-untransfected stem cells; N3: NPOP-short hairpin negative control (NPOP-sh-NC); N4: NPOP-short hairpin-Mfn2 (NPOP-sh-Mfn2)), and four groups for prolapse (P1−P4, P1: POP-normal saline; P2: POP-untransfected stem cells; P3: POP-sh-NC; P4: POP-sh-Mfn2), respectively. Stem cells were then cultured and isolated. The expression of Mfn2 was inhibited by lentivirus transfection, and the stem cells were injected into the uterosacral ligament of the rats in each group. The expression levels of Mfn2 and procollagen 1A1/1A2/3A1 in the uterosacral ligaments of the rats were observed at 0, 7, 14, and 21 days after injection. Results: Compared to the rats in the NPOP group, the POP rats had significant prolapse. The Mfn2 expression in the uterosacral ligaments of the POP rats was significantly increased (p < 0.05, all), and the expression of procollagen 1A1/1A2/3A1 was significantly decreased (p < 0.001, all). The POP rat model maintained the same trend after 21 days (without stem cell injection). At day 14, compared to the rats in the N1 group, the Mfn2 expression in the uterosacral ligament of the rats in the N4 group was significantly decreased (p < 0.05, all), and the expression of procollagens was significantly increased (p < 0.05, all). Similarly, compared to the rats in the P1 group, the Mfn2 expression in the uterosacral ligament of the rats in the P4 group was significantly decreased (p < 0.05, all), and the expression of procollagens was significantly increased (p < 0.05, all). Similarly, on day 21, the Mfn2 mRNA and protein expression in the uterosacral ligament of the POP and NPOP rats was significantly decreased (p < 0.05, all), and the expression of procollagens was significantly increased (p < 0.05, all) in the rats in the sh-Mfn2 group (N4, P4) compared to the rats in the saline group (N1, P1). Conclusions: The downregulation of Mfn2 expression by stem cells decreased the expression of Mfn2 and increased the expression of procollagen1A1/1A2/3A1 in the uterosacral ligament of the POP rats; this effect was significant 14−21 days after the injection. Thus, Mfn2 may be a new target for POP control.

Mitofusin2 regulates the proliferation and function of fibroblasts: The possible mechanisms underlying pelvic organ prolapse development

The present study aimed to investigate the effects of Mitofusin2 (Mfn2) on the proliferation of human uterosacral ligament fibroblasts and on the expression of procollagen. We also aimed to identify the possible signal transduction pathway involved in the development of pelvic organ prolapse (POP). For this purpose, uterosacral ligaments were harvested from POP and non‑pelvic organ prolapse (NPOP) patients for fibroblast culture. Cellular proliferation and the cell cycle were assessed following transduction with lentiviral vectors for the overexpression and suppression of Mfn2. The expression levels of the proteins Mfn2, procollagens, phosphoprotein 21 wild‑type p53 activating fragment (p21Waf1), cyclin‑dependent kinase 2 (CDK2), extracellular signal‑regulated kinase1/2 (ERK1/2) and rapidly accelerated fibrosarcoma‑1 (Raf‑1) were examined. Overexpression of Mfn2 resulted in the decreased proliferation of cells and the induction of G0/G1 phase arrest. Concomitantly, the relative expression levels of procollagen proteins, CDK2 and the phosphorylation levels of ERK1/2 and Raf‑1 proteins were notably decreased, while the levels of the p21waf1 protein were increased in the Mfn2 overexpressing group. Opposing results were reported cells following Mfn2 silencing via RNA interference. The results of the present study indicated that the cell cycle of the fibroblasts, their cellular proliferation and the levels of the procollagen proteins could be inhibited via the Ras‑Raf‑ERK axis as a result of the increased levels of Mfn2 during the development of POP.

Collagen changes in pelvic support tissues in women with pelvic organ prolapse

Pelvic organ prolapse is a group of diseases caused by weakened pelvic supportive tissue, but the pathophysiology is not completely understood. Collagen is one of the most important components of the extracellular matrix in connective tissue, as it maintains the supportive functions of the pelvic floor. Collagen I and III are two major subtypes in pelvic tissues. With conflicting results of different studies, changes of their content and ratio are still disputed. The structure of collagen fibrils of pelvic organ prolapse patients become loose, disorderly and discontinuous and become stiffer than control group. Strong mechanical stress and imbalance matrix metalloproteinases /tissue-derived inhibitors of metalloproteinases can lead to collagen anabolism abnormalities causing changes of collagen content and structure. These changes are inter-influenced and are involved by multiple signaling pathways, including TGF-β/Smad, AGE/RAGE, MAPK, PI3K/AKT, and NF-κB. Collagen changes, including content, morphologic and biomechanical changes and catabolism abnormalities, can destroy the supportive function of the pelvic floor and are closely related to the development of pelvic organ prolapse. Epidemiological data also show a genetic predisposition to collagen changes. Research about collagen changes in the pelvic floor supportive tissues is limited and controversial. Small sample sizes and different recruitment criteria, biopsy sites, and research methods make comparisons between various studies difficult. More research concerning collagen changes is needed to better understand the pathogenesis of pelvic organ prolapse.

Levator Avulsion Is Associated With Pelvic Organ Prolapse 23 Years After the First Childbirth

OBJECTIVES

This study aimed to ascertain the association between levator avulsion and pelvic organ prolapse (POP).

METHODS

This was a cross-sectional study involving 195 women enrolled in a longitudinal cohort study and seen 20 years after an index birth. All had a standardized patient-administered questionnaire, the International Continence Society Pelvic Organ Prolapse Quantification assessment and 4D translabial ultrasound. Main outcome measures were objective POP clinically and on translabial ultrasound. Postimaging assessment of levator integrity and sonographically determined pelvic organ descent was done blinded against other data.

RESULTS

Of 195 women who were seen a mean of 23 (range, 19.4-46.2) years after their first birth, one declined ultrasound assessment and was excluded, leaving 194. Mean age was 50.2 (range 36.9-66.5) years with a mean body mass index (BMI) of 27.6 (range, 18.3-54.3) kg/m² . Median parity was 3 (range 1-14). Ninety-one percent (n = 176) had delivered vaginally. Eighteen percent (n = 34) were symptomatic of prolapse. Clinically, 36% (n = 69) had significant POP. Levator avulsion was diagnosed in 16% (n = 31). Mean levator avulsion defect score was 2.2 (range, 0-12). On univariate analysis, levator avulsion and levator avulsion defect score were associated with clinically and sonographically significant POP, that is, odds ratio 2.6 (1.2-5.7), P = .01; and odds ratio 3.3 (1.4-7.7); P = .003, respectively; Ba (P < .001); bladder (P < .001); uterine (P < .001) and rectal ampulla (P = .009) descent, but not POP symptoms, C, and Bp. Multivariate analysis controlling for potential confounders confirmed our findings.

CONCLUSIONS

Levator avulsion is associated with female pelvic organ prolapse, especially of the anterior and central compartments. This association may become stronger with aging.

Correlations between Mitofusin 2 Expression in Fibroblasts and Pelvic Organ Prolapse: An In vitro Study

BACKGROUND

Both Mitofusin 2 (Mfn2) and pelvic organ prolapse (POP) are related to aging. The aim of the present study was to investigate the variations of Mfn2 expression in the uterosacral ligaments of patients with and/or without POP and their correlations with the expression of procollagen.

METHODS

Fibroblasts were cultured using tissue specimens that were harvested from the uterosacral ligaments of POP and non-POP (NPOP) patients (n = 10 for each group) from September 2016 to December 2016. The Cell Counting Kit-8 (CCK-8) assay was used to compare the differences in cell proliferation between the two groups. Relative quantitative reverse transcription-polymerase chain reaction and Western blotting assays were employed to assess the differences in the mRNA and protein expression levels of Mfn2 and procollagen 1A1/1A2/3A1 between the two groups. The changes in procollagen expression were assessed following the downregulation of Mfn2 in the POP group using RNAi. The data were assessed with independent sample t- test or general linear model univariate analysis using the SPSS 13.0 software.

RESULTS

The results from CCK-8 assay indicated that cell viability in the POP group was significantly lower compared with that of the NPOP group (td5, 7, 9, 11= -5.925, -6.851, -9.129, and -9.661, respectively, all P < 0.001, from D5 to D11). The mRNA and protein expression levels of Mfn2 in the cultured fibroblasts of the POP group were significantly higher compared with those of the NPOP group (mRNA: t = 2.425, P = 0.032; protein: t = 2.392, P = 0.037, respectively), whereas only the expression levels of procollagen 1A1/1A2/3A1 were significantly higher in the NPOP group (mRNA: t = -2.165, P1A1 = 0.041; t = -2.741, P1A2 = 0.026; t = -2.147, P3A1 = 0.045, respectively; protein: t = -2.418, P1A1 = 0.029; t = -2.405, P1A2 = 0.033; t = -2.470, P3A1 = 0.012, respectively). The expression levels of procollagen in the POP group increased following the downregulation of Mfn2.

CONCLUSIONS

The proliferation rate and cell viability of the fibroblasts in the POP group were significantly lower compared with those in the NPOP group. In the POP fibroblasts, Mfn2 expression was increased, while procollagen expression was decreased.

Advanced glycation end products decrease collagen I levels in fibroblasts from the vaginal wall of patients with POP via the RAGE, MAPK and NF-κB pathways

The present study was carried out to observe the impact of advanced glycation end products (AGEs) on collagen I derived from vaginal fibroblasts in the context of pelvic organ prolapse (POP), and explore the downstream effects on MAPK and nuclear factor-κB (NF-κB) signaling. After treating primary cultured human vaginal fibroblasts (HVFs) derived from POP and non-POP cases with AGEs, cell counting was carried out by sulforhodamine B. The expression levels of collagen I, receptor of advanced glycation end products (RAGE), matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were detected by western blot analysis and PCR. RAGE, MAPK and NF-κB were molecularly and pharmacologically-inhibited by siRNA, SB203580 and PDTC, respectively, and downstream changes were detected by western blot analysis and PCR. Inhibition of HVF proliferation by AGEs occurred more readily in POP patients than that noted in the controls. After treatment with AGEs, collagen I levels decreased and MMP-1 levels increased to a greater extent in the HVFs of POP than that noted in the controls. During this same period, RAGE and TIMP-1 levels remained stable. Following treatment with AGEs and RAGE pathway inhibitors by siRNA, SB203580 and PDTC, the impact induced by AGEs was diminished. The inhibition of p-p38 MAPK alone was not able to block the promoting effect of AGEs on the levels of NF-κB, which suggests that AGEs may function through other pathways, as well as p-p38 MAPK. On the whole, this study demonstrated that AGEs inhibited HVF proliferation in POP cases and decreased the expression of collagen I through RAGE and/or p-p38 MAPK and NF-κB-p-p65 pathways. Our results provide important insights into the collagen I metabolism in HVFs in POP.

Role of transforming growth factor β‑1 in the pathogenesis of pelvic organ prolapse: A potential therapeutic target

The present study aimed to reveal the metabolic alterations of the extracellular matrix (ECM) in uterosacral ligament (USL) with pelvic organ prolapse (POP) and to explore the role of transforming growth factor-β1 (TGF-β1) in pathogenesis of POP. For this purpse, 60 participants who underwent hysterectomy for benign indications were enrolled, 30 of which had symptomatic POP (grade II, III or IV) and composed the POP group, and the other 30 had asymptomatic POP (grade I or less) and served as the controls. Collagen fibers, elastin, matrix metalloproteinase (MMP)-2/9, tissue inhibitor of matrix metalloproteinases (TIMP)-2 and TGF-β1 were examined by Masson's trichrome staining, immunohistochemistry and RT-qPCR using USL biopsies. In vitro, human USL fibroblasts (hUSLFs) were primary cultured, pre-treated with recombinant TGF-β1 (0, 5, or 10 ng/ml) and then subjected to cyclic mechanical stretching (CMS; 0 or 5,333 με strain). Changes in the expression levels of collagen type I/III, elastin, TIMP-2, MMP-2/9 and Smad were detected. Our results revealed that at the tissue level, the expression of collagen fibers, elastin, TIMP-2 and TGF-β1 was significantly reduced in the POP group, while the activities of MMP-2/9 were significantly upregulated, compared with the control group. Statistical analysis indicated that the mRNA expression of TGF-β1 inversely correlated with the severity of POP partially. Our in vitro experimental data demonstrated that a CMS of 5333 με strain promoted the degradation of ECM proteins, inhibited the synthesis of TIMP-2, and upregulated the proteolytic activities of MMP-2/9. Pre-treatment with TGF-β1 attenuated the loss of ECM by stimulating the synthesis of TIMP-2 and inhibiting the activities of MMP-2/9 through the TGF-β1/Smad3 signaling pathway. On the whole, our data indicate that the reduced anabolism and increased catabolism of ECM proteins in USL are the pathological characteristics of POP. TGF-β1 not only has a specific value in predicting the severity of POP, but should also be considered as a novel therapeutic target for POP.

MicroRNA-92 expression may be associated with reduced estrogen receptor β1 mRNA levels in cervical portion of uterosacral ligaments in women with pelvic organ prolapse

OBJECTIVE

This study examined microRNA-92 (miR-92) expression level in relation to the mRNA level of its potential target gene, estrogen receptor β1 (ERβ1), in female patients diagnosed with pelvic organ prolapse (POP).

STUDY DESIGN

Between July 2012 and September 2014, a total of 104 patients were recruited at the First Affiliated Hospital of Sun Yat-sen University, which included 56 POP patients and 48 non-POP control subjects. Based on POP-Q score, the POP patients were further categorized into POP II and POP III groups. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to quantify miR-92 expression level. ERβ1 tissue expression was measured by western blot and immunohistochemistry (IHC) methods. SPSS 19.0 software was used for statistical analysis.

RESULTS

No remarkable differences were observed between the POP group and non-POP group, and between the POP II and POP III groups, with respect to age, body mass index (BMI), parity, menopause status, and family history of POP. The expression level of miR-92 in the POP group was dramatically higher than the non-POP group (P<0.05). Consistent with the disease status, miR-92 expression level in POP III group was markedly higher than the POP II group (P<0.05). Western blot analysis revealed significantly reduced levels of ERβ1 in the POP group compared to the non-POP group, with similar results obtained between the POP III and POP II groups (all P<0.05). IHC results showed ERβ1 staining mainly in the nucleus and semi-quantitative measurements, expressed as positive expression rate, revealed that ERβ1 level in the POP group was clearly lower than non-POP group. Finally, statistical analysis of IHC results from uterosacral ligament tissue showed inverse correlation between miR-92 and ERβ1 expression levels in POP patients (P<0.05).

CONCLUSIONS

Our results revealed increased miR-92 expression and decreased ERβ1 level in uterosacral ligaments of women diagnosed with POP, compared to non-POP subjects POP III patients exhibited more severe changes than POP II patients. Further, ERβ1expression is inversely correlated to miR-92 expression. Taken together, our results suggest that miR-92 and ERβ1 expression levels may be used as reliable diagnostic markers for assessing the severity of POP.

Novel minimally invasive laser treatment of urinary incontinence in women

BACKGROUND AND OBJECTIVE

Urinary incontinence (UI) is a common disorder that affects women of various ages and impacts all aspects of life. Our aim was to evaluate the non-invasive erbium:yttrium-aluminum-garnet (Er:YAG) laser that exploits its thermal effect and has been used in reconstructive and rejuvenation surgery as a potential treatment strategy for stress UI (SUI) and mixed UI (MUI).

STUDY DESIGN/MATERIALS AND METHODS

We included 175 women (aged 49.7 ± 10 years) with newly diagnosed SUI (66% of women) and MUI (34%), respectively. Patients were clinically examined and classified by incontinence types (SUI and MUI) and grades (mild, moderate, severe, and very severe) using International Consultation on Incontinence Modular Questionnaire (ICIQ) and assessing Incontinence Severity Index (ISI). Using Er:YAG laser, we performed on average 2.5 ± 0.5 procedures in each woman separated by a 2 month period. At each session, clinical examination was performed, ICIQ and ISI assessed and treatment discomfort measured with visual analog system (VAS) pain scale, and adverse effects and patients' satisfaction were followed. Follow-ups were performed at 2, 6, and 12 months after the treatment.

RESULTS

After the treatment, ISI decreased for 2.6 ± 1.0 points in patients diagnosed with mild UI before the treatment, for 3.6 ± 1.4 points in those with moderate UI, for 5.7 ± 1.8 points in those with severe UI and for 8.4 ± 2.6 in those with very severe UI (P < 0.001, paired samples t-test). Altogether, in 77% patients diagnosed with SUI, a significant improvement was found after treatment, while only 34% of women with MUI exhibited no UI at one year follow-up. Age did not affect the outcome. No major adverse effects were noticed in either group.

CONCLUSION

The results of our study, have shown that new non-invasive Er:YAG laser could be regarded as a promising additional treatment strategy for SUI with at least one year lasting positive effects. On the other hand, it does not seem appropriate for treating MUI.