Vaginal Expression of LOXL1 in Premenopausal and Postmenopausal Women With Pelvic Organ Prolapse

Advancing our understanding of genetic risk factors and potential personalized strategies for pelvic organ prolapse

Pelvic organ prolapse is a common gynecological condition with limited understanding of its genetic background. In this work, we perform a genome-wide association meta-analysis comprising 28,086 cases and 546,291 controls from European ancestry. We identify 19 novel genome-wide significant loci, highlighting connective tissue, urogenital and cardiometabolic as likely affected systems. Here, we prioritize many genes of potential interest and assess shared genetic and phenotypic links. Additionally, we present the first polygenic risk score, which shows similar predictive ability (Harrell C-statistic (C-stat) 0.583, standard deviation (sd) = 0.007) as five established clinical risk factors combined (number of children, body mass index, ever smoked, constipation and asthma) (C-stat = 0.588, sd = 0.007) and demonstrates a substantial incremental value in combination with these (C-stat = 0.630, sd = 0.007). These findings improve our understanding of genetic factors underlying pelvic organ prolapse and provide a solid start evaluating polygenic risk scores as a potential tool to enhance individual risk prediction.

Although pelvic organ prolapse is a common gynecological condition, the genetic component of disease risk is not well known. Here the authors find common genetic variants associated with the disease and present a polygenic risk score to enhance individual risk prediction.

The rs2165241 polymorphism of the Loxl1 gene in postmenopausal women with pelvic organ prolapse

OBJECTIVE

This study aimed to verify the presence of polymorphism rs2165241 of the lysyl oxidase-like 1 (Loxl1) gene and its association with pelvic organ prolapse (POP) in Brazilian women and determine risk factors for POP development.

METHODS

The study was previously approved by the local research and ethics board. Postmenopausal women were included and divided into POP (stages III and IV) and control (stages 0 and I) groups. Peripheral blood samples were collected, and the DNA sequence of interest was analyzed by real-time reverse-transcriptase polymerase chain reaction. We used logistic regression and considered a recessive model of inheritance for the analysis, with p < 0.05 for significance.

RESULTS

A total of 836 women were assessed: 426 POP cases and 410 controls. The frequencies of CC, CT and TT genotypes were similar in both groups. Age (odds ratio [OR] = 1.1, 95% confidence interval [CI] = 1.07; 1.14), number of vaginal births (OR = 17.06, 95% CI = 5.94; 48.97), family history (OR = 2.87, 95% CI = 1.57; 5.22) and weight of largest newborn (OR = 1.001, 95% CI = 1.0003; 1.001) were independent risk factors for POP, while multiple cesarean sections (two or more) was protective (OR = 0.17, 95% CI = 0.07; 0.42).

CONCLUSION

No association was detected between rs2165241 of the Loxl1 gene and POP.

Mouse Knockout Models for Pelvic Organ Prolapse: a Systematic Review

INTRODUCTION AND HYPOTHESIS

Mouse knockout (KO) models of pelvic organ prolapse (POP) have contributed mechanistic evidence for the role of connective tissue defects, specifically impaired elastic matrix remodeling. Our objective was to summarize what mouse KO models for POP are available and what have we learned from these mouse models about the pathophysiological mechanisms of POP development.

METHODS

We conducted a systematic review and reported narrative findings according to PRISMA guidelines. Two independent reviewers searched PubMed, Scopus and Embase for relevant manuscripts and conference abstracts for the time frame of January 1, 2000, to March 31, 2021. Conference abstracts were limited to the past 5 years.

RESULTS

The search strategy resulted in 294 total titles. We ultimately included 25 articles and an additional 11 conference abstracts. Five KO models have been studied: Loxl1, Fbln5, Fbln3, Hoxa11 and Upii-sv40t. Loxl1 and Fbln5 KO models have provided the most reliable and predictable POP phenotype. Loxl1 KO mice develop POP primarily from failure to heal after giving birth, whereas Fbln5 KO mice develop POP with aging. These mouse KO models have been used for a wide variety of investigations including genetic pathways involved in development of POP, biomechanical properties of the pelvic floor, elastic fiber deposition, POP therapies and the pathophysiology associated with mesh complications.

CONCLUSIONS

Mouse KO models have proved to be a valuable tool in the study of specific genes and their role in the development and progression of POP. They may be useful to study POP treatments and POP complications.

Mass cytometry and transcriptomic profiling reveal body-wide pathology induced by Loxl1 deficiency

Objective

The loss of LOXL1 expression reportedly leads to the prolapse of pelvic organs or to exfoliation syndrome glaucoma. Increasing evidence suggests that LOXL1 deficiency is associated with the pathogenesis of several other diseases. However, the characterization of the systemic functions of LOXL1 is limited by the lack of relevant investigative technologies.

Materials and Methods

To determine the functions of LOXL1, a novel method for body‐wide organ transcriptome profiling, combined with single‐cell mass cytometry, was developed. A body‐wide organ transcriptomic (BOT) map was created by RNA‐Seq of tissues from 17 organs from both Loxl1 knockout (KO) and wild‐type mice.

Results

The BOT results indicated the systemic upregulation of genes encoding proteins associated with the immune response and proliferation processes in multiple tissues of KO mice, and histological and immune staining confirmed the hyperplasia and infiltration of local immune cells in the tissues of KO mice. Furthermore, mass cytometry analysis of peripheral blood samples revealed systemic immune changes in KO mice. These findings were well correlated with results obtained from cancer databases. Patients with tumours had higher Loxl1 mutation frequencies, and patients with Loxl1‐mutant tumours showed the upregulation of immune processes and cell proliferation and lower survival rates.

Conclusion

This study provides an effective strategy for the screening of gene functions in multiple organs and also illustrates the important biological roles of LOXL1 in the cells of multiple organs as well as in systemic immunity.

Elastin homeostasis is altered with pelvic organ prolapse in cultures of vaginal cells from a lysyl oxidase-like 1 knockout mouse model

Pelvic organ prolapse (POP) decreases quality of life for many women, but its pathophysiology is poorly understood. We have previously shown that Lysyl oxidase‐like 1 knockout (Loxl1 KO) mice reliably prolapse with age and increased parity, similar to women. Both this model and clinical studies also indicate that altered elastin metabolism in pelvic floor tissues plays a role in POP manifestation, although it is unknown if this is a cause or effect. Using Loxl1 KO mice, we investigated the effects of genetic absence of Loxl1, vaginal parity, and presence of POP on the expression of genes and proteins key to the production and regulation of elastic matrix. Cultured cells isolated from vaginal explants of mice were assayed with Fastin for elastic matrix, as well as RT‐PCR and Western blot for expression of genes and proteins important for elastin homeostasis. Elastin synthesis significantly decreased with absence of LOXL1 and increased with parity (p < .001), but not with POP. Cells from prolapsed mice expressed significantly decreased MMP‐2 (p < .05) and increased TIMP‐4 (p < .05). The results suggest changes to elastin structure rather than amounts in prolapsed mice as well as poor postpartum elastin turnover, resulting in accumulation of damaged elastic fibers leading to abnormal tropoelastin deposition. POP may thus, be the result of an inability to initiate the molecular mechanisms necessary to clear and replace damaged elastic matrix in pelvic floor tissues after vaginal birth.

Quantitative Morphometry of Elastic Fibers in Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is common among older women who have delivered children vaginally. While the pathophysiology is not fully delineated, POP can occur in part from insufficient repair of disrupted elastic matrix fibers. Quantification of structural changes to elastic fibers has not been described previously for POP. The goal of this paper is to present a validated technique for morphometric analysis of elastic fibers in vaginal tissue cultures from lysyl oxidase like-1 knock out (LOXL1 KO) mice with POP. The effect of LOXL1 KO, effect of POP, effect of culture, and effect of elastogenic treatment on the changes in elastin fiber characteristics were tested using vaginal tissues from wild type multiparous (WT), LOXL1 KO multiparous prolapsed (POP) and LOXL1 KO multiparous non-prolapsed (NP) mice. Our results show significantly higher mean aspect ratio, maximum diameter and perimeter length in POP compared to NP after 3 weeks of tissue culture. Further, treatment of POP tissues in culture with growth factors with previously documented elastogenic effects caused a significant increase in the mean area and perimeter length of elastic fibers. This technique thus appears to be useful in quantifying structural changes and can be used to assess the pathophysiology of POP and the effect of elastogenic treatments with potential for POP.

Single-cell transcriptome profiling of the vaginal wall in women with severe anterior vaginal prolapse

Anterior vaginal prolapse (AVP) is the most common form of pelvic organ prolapse (POP) and has deleterious effects on women's health. Despite recent advances in AVP diagnosis and treatment, a cell atlas of the vaginal wall in AVP has not been constructed. Here, we employ single-cell RNA-seq to construct a transcriptomic atlas of 81,026 individual cells in the vaginal wall from AVP and control samples and identify 11 cell types. We reveal aberrant gene expression in diverse cell types in AVP. Extracellular matrix (ECM) dysregulation and immune reactions involvement are identified in both non-immune and immune cell types. In addition, we find that several transcription factors associated with ECM and immune regulation are activated in AVP. Furthermore, we reveal dysregulated cell-cell communication patterns in AVP. Taken together, this work provides a valuable resource for deciphering the cellular heterogeneity and the molecular mechanisms underlying severe AVP.

Role of lysyl oxidase like 1 in regulation of postpartum connective tissue metabolism in the mouse vagina†

Pelvic organ prolapse (POP) in lysyl oxidase like-1 knockout (Loxl1 KO) mice occurs primarily in parous mice and is rare in nulliparous mice. We determined the effect of Loxl1 deficiency on postpartum regulation of connective tissue metabolism genes and degradative enzyme activity in the vagina at 20 days gestation or 4 h, 48 h, 7 days, 15 days, 25 days, 7 weeks, or 12 weeks postpartum. Nulliparous Loxl1 KO and wildtype (WT) mice aged 11, 18, or 23 weeks were controls. Gene expression and enzyme activity were assessed using real-time quantitative reverse transcription PCR and fluorescein conjugated gelatin zymography, respectively. Parity, but not aging, had a significant influence on gene expression both with time postpartum and between KO and WT mice. Mmp2, Timp1, Timp2, Timp3, Timp4, Col1a1, Col3a1, Acta2, and Bmp1 were differentially expressed between KO and WT mice. Correlational analysis of gene-gene pairs revealed 10 significant differences between parous KO and WT groups, 5 of which were due to lack of co-expression of Bmp1 in KO mice. The overall enzyme activity that could be attributed to MMPs was significantly higher in WT compared to KO mice both 25 days and 12 weeks postpartum, and MMP activity was significantly lower 15 days and 25 days postpartum compared to KO nulliparous controls, but not WT. These findings suggest that Loxl1 deficiency combined with parity has a significant impact on postpartum regulation of connective tissue metabolism, particularly as it relates to co-expression of Bmp1 and altered proteolytic activity.

Role of sex steroid hormones in pelvic organ prolapse

OBJECTIVE

Pelvic organ prolapse (POP) affects a significant percentage of women and contributes to major healthcare costs both in the United States and worldwide. This review examines the current understanding of the role of sex steroid hormones (estrogens, androgens, and progesterone) in POP in premenopausal, perimenopausal, and postmenopausal women.

METHODS

We reviewed the relevant studies on POP related to estrogens, androgens, and progesterone in both animal models and humans.

RESULTS

Estrogen has a profound influence on the synthesis and metabolism of pelvic connective tissues, and may have the ability to both prevent POP and improve prognosis if used therapeutically. There is limited research regarding the role of androgens and progesterone and their receptors in POP and results so far have been contradictory, warranting further study to determine whether changes in androgen and progesterone receptor expression are a cause or effect of POP.

CONCLUSIONS

Because of the role that estrogen plays in maintaining the integrity of pelvic floor connective tissues, we propose that rigorous and well-controlled studies are needed on the role of exogenous estrogen administration as a form of POP prevention. : Video Summary:http://links.lww.com/MENO/A583.

Transcriptional Regulation of Connective Tissue Metabolism Genes in Women With Pelvic Organ Prolapse

OBJECTIVE

The aim of this study was to compare differences in expressions and relationships between key genes involved in extracellular matrix metabolism and tissue cellularity in women with and without pelvic organ prolapse (POP).

METHODS

A total of 80 biopsies (anterior cuff, posterior cuff, and/or leading edge) were obtained from 30 women: n = 10 premenopausal without POP (controls), n = 10 premenopausal with POP, and n = 10 postmenopausal with POP. Quantitative reverse-transcriptase polymerase chain reaction was used to assess gene expression of bone morphogenetic protein 1 (BMP1), collagen types I (COL1) and III (COL3), relaxin family peptide receptor 1 (RXFP1), matrix metallopeptidase 2, and TIMP metallopeptidase inhibitors 2 and 3. Hematoxylin and eosin staining was used to assess cellularity of the connective tissue layer. Kruskal-Wallis test, Mann-Whitney U test, Pearson correlation, or linear regression analyses were used, as appropriate.

RESULTS

Bone morphogenetic protein 1 expression was significantly up-regulated in patients with POP compared with controls. Bone morphogenetic protein 1 expression was correlated with COL1 expression in all groups but only correlated with TIMP metallopeptidase inhibitor 3 expression in controls. Similarly, COL3 expression was correlated with RXFP1 expression in women with POP but not in controls. The degree of dependence (slope of the regression line) between COL1 and COL3 expressions was significantly elevated in premenopausal women with POP compared with the other 2 groups. The slopes between COL1-COL3, COL3-matrix metallopeptidase 2, COL1-RXFP1, and COL3-RXFP1 expressions were significantly lower in postmenopausal women compared with premenopausal women with POP. No differences were found in overall tissue cellularity.

CONCLUSIONS

Bone morphogenetic protein 1 expression may play a significant role in the pathophysiology of POP. The finding that BMP1 expression was correlated with COL1 expression in all groups suggests a conserved association between BMP1 and collagen synthesis in the vaginal wall. The elevated slope between COL1 and COL3 expressions may be associated with early (premenopausal) development of POP. The expression of RXFP1 in postmenopausal women and its altered intergene regulation suggests a role for RXFP1 in connective tissue metabolism outside pregnancy.

Expression changes in pelvic organ prolapse: a systematic review and in silico study

Pelvic organ prolapse (POP) is a highly disabling condition common for a vast number of women worldwide. To contribute to existing knowledge in POP pathogenesis, we performed a systematic review of expression studies on both specific gene and whole-genome/proteome levels and an in silico analysis of publicly available datasets related to POP development. The most extensively investigated genes in individual studies were related to extracellular matrix (ECM) organization. Three premenopausal and two postmenopausal sets from two Gene Expression Omnibus (GEO) studies (GSE53868 and GSE12852) were analyzed; Gene Ontology (GO) terms related to tissue repair (locomotion, biological adhesion, immune processes and other) were enriched in all five datasets. Co-expression was higher in cases than in controls in three premenopausal sets. The shared between two or more datasets up-regulated genes were enriched with those related to inflammatory bowel disease (IBD) in the NHGRI GWAS Catalog. ECM-related genes were not over-represented among differently expressed genes. Up-regulation of genes related to tissue renewal probably reflects compensatory mechanisms aimed at repair of damaged tissue. Inefficiency of this process may have different origins including age-related deregulation of gene expression.

Major review: Exfoliation syndrome; advances in disease genetics, molecular biology, and epidemiology

Exfoliation syndrome (XFS) is a common age-related disorder that leads to deposition of extracellular fibrillar material throughout the body. The most recognized disease manifestation is exfoliation glaucoma (XFG), which is a common cause of blindness worldwide. Recent developments in XFS genetics, cell biology and epidemiology have greatly improved our understanding of the etiology of this complex inherited disease. This review summarizes current knowledge of XFS pathogenesis, identifies gaps in knowledge, and discusses areas for future research.

Methylation of LOXL1 Promoter by DNMT3A in Aged Human Skin Fibroblasts

Lysyl oxidase-like 1 (LOXL1) is an amino-oxidase involved in maturation of elastic fibers. Its downregulation has been associated with elastic fibers repair loss in aging aorta, lung, ligament, and skin. Several evidences of LOXL1 epigenetic silencing by promoter methylation were reported in cancer and cutis laxa syndrome. We hypothesized that this mechanism could be implicated in skin aging process, as far as elastic fibers are also concerned. Anti-DNMT3A chromatin immunoprecipitation was conducted with nuclear extracts from skin fibroblasts isolated from young and elderly individuals, and showed a higher level of DNMT3A protein binding to the LOXL1 promoter in older cells concomitantly to the decrease of LOXL1 mRNA expression and the increase of LOXL1 promoter methylation. Using luciferase reporter assay driven by LOXL1 promoter in HEK293 cells, we demonstrated that LOXL1 transcriptional activity was dramatically reduced when a recombinant DNMT3A was concomitantly overexpressed. LOXL1 promoter transcriptional activity was restored in the presence of a broad-spectrum inhibitor of DNMT activity, 5-aza-2'-deoxycytidine. Finally, to assess whether the interplay between DNMT3A and LOXL1 promoter could be targeted to increase LOXL1 mRNA expression level, an Origanum majorana extract was selected among 43 plant extracts as a new inhibitor of human DNMT3A activity to restore LOXL1 secretion without cytotoxicity in aged skin fibroblasts.