Changes in IL-16 Expression in the Ovary during Aging and Its Potential Consequences to Ovarian Pathology

The physiological role of macrophages in reproductive organs

Background

Macrophages are essential immune cells critical to reproductive physiology. They regulate key processes such as follicular development, ovulation, and luteinization in the ovaries. Macrophages are also involved in endometrial remodeling, immune tolerance, and placentation in the uterus.

Methods

This review examined the biological characteristics of macrophages and their role in ovarian, uterine, and fallopian tube physiology. It focused on findings from both animal and human studies to provide a comprehensive understanding of macrophage functions.

Main Findings

In the ovaries, M1 macrophages play a role in folliculogenesis and ovulation through the inflammatory and angiogenic pathways. Macrophages also maintain the corpus luteum and vascular integrity. In the uterus, macrophages regulate tissue repair and remodeling during the menstrual cycle and play a critical role in implantation by maintaining immune tolerance and supporting decidualization. Dysregulation of the M1/M2 balance can cause implantation failure. In the fallopian tubes, macrophages mediate tissue repair and immune responses. Macrophage polarization dynamically adapts to physiological and pathological conditions in all reproductive organs highlighting the functional plasticity of these cells.

Conclusion

Macrophage polarization and functions are pivotal in maintaining reproductive health. Hence, understanding the role of macrophages in various reproductive organs provides a foundation for developing new therapies.

Association of the Single Nucleotide Polymorphisms rs11556218, rs4778889, rs4072111, and rs1131445 of the Interleukin-16 Gene with Ovarian Cancer

Single nucleotide polymorphisms (SNPs) of the IL-16 gene have been reported to influence the risk of several cancers, but their role in ovarian cancer (OC) has not been studied. Using the restriction fragment length polymorphism (PCR-RFLP) method, we examined four IL-16 SNPs: rs11556218 (T > G), rs4778889 (T > C), rs4072111 (C > T), and rs1131445 (T > C) in blood samples from 413 women of Central European descent, including 200 OC patients and 213 healthy controls. Among the patients, 62% were postmenopausal, 84.5% were diagnosed in late stages (FIGO IIb-IV), and 73.5% had high-grade serous OC (HGSOC). Minor allele frequencies in controls were 9.2% for rs11556218 (G allele), 13.7% for rs4778889 (C allele), 10.4% for rs4072111 (T allele), and 32.3% for rs1131445 (C allele). We found significant associations of rs11556218 (G vs. T allele: OR 2.76, 95% CI 1.84-4.14, p < 0.0001) with elevated OC risk in the whole cohort (p < 0.001) and in both premenopausal (p < 0.001) and postmenopausal (p = 0.001) subgroups. These associations remained significant across heterozygote (p < 0.001), dominant (p < 0.001), and overdominant (p < 0.001) models. IL-16 rs4778889 was associated with OC risk predominantly in premenopausal women (p < 0.0001 in almost all models). In the whole cohort, the C allele was associated with OC risk (OR 1.54, CI 95% 1.06-2.23, p = 0.024), and the association of rs4778889 was significant in dominant (p = 0.019), overdominant (p = 0.033), and heterozygote (p = 0.027) models. Furthermore, rs4778889 was linked with HGSOC (p = 0.036) and endometriosis-related OC subtypes (p = 0.002). No significant associations were found for rs4072111 or rs1131445 (p = 0.81 or 0.47, respectively). In conclusion, rs11556218 and rs4778889 SNPs are associated with OC risk, especially in premenopausal women.

An eQTL-based approach reveals candidate regulators of LINE-1 RNA levels in lymphoblastoid cells

Long interspersed element 1 (LINE-1; L1) are a family of transposons that occupy ~17% of the human genome. Though a small number of L1 copies remain capable of autonomous transposition, the overwhelming majority of copies are degenerate and immobile. Nevertheless, both mobile and immobile L1s can exert pleiotropic effects (promoting genome instability, inflammation, or cellular senescence) on their hosts, and L1's contributions to aging and aging diseases is an area of active research. However, because of the cell type-specific nature of transposon control, the catalogue of L1 regulators remains incomplete. Here, we employ an eQTL approach leveraging transcriptomic and genomic data from the GEUVADIS and 1000Genomes projects to computationally identify new candidate regulators of L1 RNA levels in lymphoblastoid cell lines. To cement the role of candidate genes in L1 regulation, we experimentally modulate the levels of top candidates in vitro, including IL16, STARD5, HSD17B12, and RNF5, and assess changes in TE family expression by Gene Set Enrichment Analysis (GSEA). Remarkably, we observe subtle but widespread upregulation of TE family expression following IL16 and STARD5 overexpression. Moreover, a short-term 24-hour exposure to recombinant human IL16 was sufficient to transiently induce subtle, but widespread, upregulation of L1 subfamilies. Finally, we find that many L1 expression-associated genetic variants are co-associated with aging traits across genome-wide association study databases. Our results expand the catalogue of genes implicated in L1 RNA control and further suggest that L1-derived RNA contributes to aging processes. Given the ever-increasing availability of paired genomic and transcriptomic data, we anticipate this new approach to be a starting point for more comprehensive computational scans for regulators of transposon RNA levels.

New insight into the role of macrophages in ovarian function and ovarian aging

Macrophages (MΦs) are the most abundant leukocytes in mammalian ovaries that have heterogeneity and plasticity. A body of evidence has indicated that these cells are important in maintaining ovarian homeostasis and they play critical roles in ovarian physiological events, such as folliculogenesis, ovulation, corpus luteum formation and regression. As females age, ovarian tissue microenvironment is typified by chronic inflammation with exacerbated ovarian fibrosis. In response to specific danger signals within aged ovaries, macrophages polarize into different M1 or M2 phenotypes, and specialize in unique functions to participate in the ovarian aging process. In this review, we will focus on the physiologic roles of MΦs in normal ovarian functions. Furthermore, we will discuss the roles of MΦs in the process of ovarian senescence, as well as the novel techniques applied in this field.

Facilitation of Ovarian Response by Mechanical Force-Latest Insight on Fertility Improvement in Women with Poor Ovarian Response or Primary Ovarian Insufficiency

The decline in fertility in aging women, especially those with poor ovarian response (POR) or primary ovarian insufficiency (POI), is a major concern for modern IVF centers. Fertility treatments have traditionally relied on gonadotropin- and steroid-hormone-based IVF practices, but these methods have limitations, especially for women with aging ovaries. Researchers have been motivated to explore alternative approaches. Ovarian aging is a complicated process, and the deterioration of oocytes, follicular cells, the extracellular matrix (ECM), and the stromal compartment can all contribute to declining fertility. Adjunct interventions that involve the use of hormones, steroids, and cofactors and gamete engineering are two major research areas aimed to improve fertility in aging women. Additionally, mechanical procedures including the In Vitro Activation (IVA) procedure, which combines pharmacological activators and fragmentation of ovarian strips, and the Whole Ovary Laparoscopic Incision (WOLI) procedure that solely relies on mechanical manipulation in vivo have shown promising results in improving follicle growth and fertility in women with POR and POI. Advances in the use of mechanical procedures have brought exciting opportunities to improve fertility outcomes in aging women with POR or POI. While the lack of a comprehensive understanding of the molecular mechanisms that lead to fertility decline in aging women remains a major challenge for further improvement of mechanical-manipulation-based approaches, recent progress has provided a better view of how these procedures promote folliculogenesis in the fibrotic and avascular aging ovaries. In this review, we first provide a brief overview of the potential mechanisms that contribute to ovarian aging in POI and POR patients, followed by a discussion of measures that aim to improve ovarian folliculogenesis in aging women. At last, we discuss the likely mechanisms that contribute to the outcomes of IVA and WOLI procedures and potential future directions.

Sex-Specific Associations between Serum IL-16 Levels and Sarcopenia in Older Adults

Epidemiological studies of older adults have suggested a differential sex-specific prevalence of sarcopenia, which is a condition characterized by a progressive loss of skeletal muscle mass and function. Recently, we collected serum samples from 80 fully evaluated older adults and identified CXCL12α as a sex-independent serum marker of sarcopenia. Here, we used this serum collection to find potential sex-specific serum markers via the simultaneous quantification of 34 inflammatory cytokines/chemokines. The appendicular skeletal muscle index (ASMI) was used as a decisive criterion for diagnosing sarcopenia. A Pearson correlation analysis revealed a negative correlation between ASMI and serum IL-16 in females only (p = 0.021). Moreover, women with sarcopenia exhibited significantly higher IL-16 (p = 0.025) serum levels than women in a control group. In contrast, males with sarcopenia had lower IL-16 (p = 0.013) levels than males in a control group. The further use of Fisher's exact test identified obesity (p = 0.027) and high serum levels of IL-16 (p = 0.029) as significant risk factors for sarcopenia in females. In male older adults, however, malnutrition (p = 0.028) and low serum levels of IL-16 (p = 0.031) were the most significant risk factors for sarcopenia. The differential sex-specific associations of IL-16 in older adults may contribute to the development of more precise regression models for future research and elucidate the role of IL-16 in the progression of sarcopenic obesity.

Expression of CISH, an Inhibitor of NK Cell Function, Increases in Association with Ovarian Cancer Development and Progression

Epithelial ovarian cancer (OVCA), a fatal malignancy of women, disseminates locally. Although NK cells mount immune responses against OVCA, tumors inhibit NK cells, and the mechanism is not well understood. Cytokines stimulate NK cells; however, chronic stimulation exhausts them and induces expression of cytokine-inducible SH2-containing protein (CISH). Tumors produce anti-inflammatory cytokine interleukin (IL)-10 which may induce NK cell exhaustion. The goal of this study was to examine if CISH expression in NK cells increases during OVCA development and to determine the mechanism(s) of OVCA-induced CISH expression in NK cells. Normal ovaries (n = 7) were used for CISH, IL-10 and GRP78 expression. In tumor ovaries, CISH was examined in early and late stages (n = 14 each, all subtypes) while IL-10 and GRP78 expression were examined in early and late stage HGSC (n = 5 each). Compared to normal, the population of CISH-expressing NK cells increased and the intensity of IL-10 and GRP78 expression was significantly higher in OVCA (p < 0.05). CISH expression was positively correlated with IL-10 expression (r = 0.52, r = 0.65, p < 0.05 at early and late stages, respectively) while IL-10 expression was positively correlated with GRP78 expression (r = 0.43, r = 0.52, p < 0.05, respectively). These results suggest that OVCA development and progression are associated with increased CISH expression by NK cells which is correlated with tumor-induced persistent cellular stress.

Changes in Nucleolin Expression during Malignant Transformation Leading to Ovarian High-Grade Serous Carcinoma

OBJECTIVE

Ovarian high-grade serous carcinoma (HGSC) is a fatal malignancy of women. Alterations in the expression of nuclear proteins are early steps in malignant transformation; nucleolin is one such protein. Changes in nucleolin expression and circulatory levels during ovarian HGSC development are unknown. The study goal was to determine if tissue and circulatory levels of nucleolin change in response to malignant transformation leading to ovarian HGSC.

METHODS

Sera, ovaries, and BRCA+ fimbria from healthy subjects, and sera and tumor tissues from patients (n = 10 each), and healthy hens and hens with HGSC were examined in exploratory and prospective studies for nucleolin expression by immunohistochemistry, immunoblotting, gene expression, and immunoassay, and analyzed by analysis of variance (ANOVA).

RESULTS

Compared with normal, nucleolin expression was higher in patients and hens with ovarian HGSC and in women with a risk of HGSC (P < 0.05). Compared with normal (1400 + 105 pg/mL, n = 8), serum nucleolin levels were 1.5 and 1.7-fold higher in patients with early- (n = 5) and late-stage (n = 5) HGSC, respectively. Additionally, serum nucleolin levels increased significantly (P < 0.05) prior to the formation of detectable masses.

CONCLUSION

This pilot study concluded that tissue and serum levels of nucleolin increase in association with malignant changes in ovaries and fimbriae leading to ovarian HGSC.

Detection of Cannabinoid Receptor Expression by Endometriotic Lesions in Women with Endometriosis as an Alternative to Opioid-Based Pain Medication

Emerging information suggests a potential role of medicinal cannabis in pain medication in addition to enhancing immune functions. Endometriosis is a disease of women of reproductive age associated with infertility and reproductive failure as well as chronic pain of varying degrees depending on the stage of the disease. Currently, opioids are being preferred over nonsteroidal anti-inflammatory drugs (NSAID) due to the latter’s side effects. However, as the opioids are becoming a source of addiction, additional pain medication is urgently needed. Cannabis offers an alternative therapy for treating the pain associated with endometriosis. Information on the use and effectiveness of cannabis against endometriotic pain is lacking. Moreover, expression of receptors for endocannabinoids by the ovarian endometriotic lesions is not known. The goal of this study was to examine whether cannabinoid receptors 1 and 2 (CB1 and CB2) are expressed by ovarian endometriotic lesions. Archived normal ovarian tissues, ovaries with endometriotic lesions, and normal endometrial tissues were examined for the presence of endometrial stromal cells using CD10 (a marker of endometrial stromal cells). Expression of CB1 and CB2 were determined by immunohistochemistry, immunoblotting, and gene expression studies. Intense expression for CB1 and CB2 was detected in the epithelial cells in ovarian endometriotic lesions. Compared with stroma in ovaries with endometriotic lesions, the expression of CB1 and CB2 was significantly higher in the epithelial cells in endometriotic lesions in the ovary ( $P<0.0001$ and $P<0.05$ , respectively). Immunoblotting and gene expression assays showed similar patterns for CB1 and CB2 protein and CNR1 (gene encoding CB1) and CNR2 (gene encoding CB2) gene expression. These results suggest that ovarian endometriotic lesions express CB1 and CB2 receptors, and these lesions may respond to cannabinoids as pain medication. These results will form a foundation for a clinical study with larger cohorts.