Gonadotrophin-releasing hormone receptor autoantibodies induce polycystic ovary syndrome-like features in a rat model

Unraveling the complexity of polycystic ovary syndrome with animal models

Polycystic ovary syndrome (PCOS) is a highly familial and heritable endocrine disorder. Over half of the daughters born to women with PCOS may eventually develop their own PCOS-related symptoms. Progress in the treatment of PCOS is currently hindered by the complexity of its clinical manifestations and incomplete knowledge of its etiopathogenesis. Various animal models, including experimentally induced, naturally occurring, and spontaneously arising ones, have been established to emulate a wide range of phenotypical and pathological traits of human PCOS. These studies have led to a paradigm shift in understanding the genetic, developmental, and evolutionary origins of this disorder. Furthermore, emerging evidence suggests that animal models are useful in evaluating state-of-the-art drugs and treatments for PCOS. This review aims to provide a comprehensive summary of recent studies of PCOS in animal models, highlighting the power of these disease models in understanding the biology of PCOS and aiding high-throughput approaches.

Immune Regulation in Polycystic Ovary Syndrome

A polycystic ovarian syndrome (PCOS) is the most common endocrine disorder affecting females . Furthermore, it is a heterogeneous disease with a variety of etiologies and outcomes. Patients frequently complain about infertility, irregular menstruation, acne, seborrheic dermatitis, hirsutism, and obesity. PCOS can be caused by hypothalamic-pituitary-ovarian axis dysfunction, heredity, or metabolic abnormalities. PCOS is characterized by chronic low-level inflammation, which includes an imbalance in pro-inflammatory factor secretion, endothelial cell dysfunction, and leukocytosis. PCOS is also distinguished by hormonal and immune dysregulation. During PCOS, immune cells and immune regulatory molecules play critical roles in maintaining metabolic homeostasis and regulating immune responses. Because of oligo/anovulation, patients with PCOS have low progesterone levels. Therefore, low progesterone levels in PCOS overstimulate the immune system, causing it to produce more estrogen, which leads to a variety of autoantibodies. This review aims to summarize the immune regulation involved in the pathogenesis of PCOS and pave the way for the development of better PCOS treatment options in the near future.

GnRH receptor-activating autoantibodies in polycystic ovary syndrome: identification of functional epitopes and development of epitope mimetic inhibitors

PURPOSE

We have recently demonstrated that gonadotrophin-releasing hormone receptor-activating autoantibodies (GnRHR-AAb) are associated with polycystic ovary syndrome (PCOS). The aim of this study was to map the antigenic epitopes of GnRHR-AAb from PCOS patients, and develop retro-inverso peptide inhibitors that specifically target GnRHR-AAb.

METHODS

Serum samples from ten GnRHR-AAb-positive PCOS patients and ten GnRHR-AAb-negative healthy controls were tested. Epitope mapping for GnRHR-AAb was performed using a set of 11 overlapping octapeptides spanning the second extracellular loop of GnRHR. Antibody-blocking effect of the designed retro-inverso peptide inhibitors was evaluated in a cell-based bioassay.

RESULTS

Two peptide sequences, FSQCVTHC and HCSFSQWW, were found to react with all PCOS sera, but not with control sera. Two retro-inverso peptides that mimic the identified epitopes, d-CHTVCQSF and d-WWQSFSCH, significantly inhibited PCOS serum IgG-induced GnRHR activation. One of these two peptide inhibitors, d-CHTVCQSF, largely suppressed autoantibody-induced GnRHR activation, suggesting that the epitope sequence FSQCVTHC may be a major functional target of GnRHR-AAb.

CONCLUSION

We have identified a dominant functional epitope for GnRHR-AAb associated with PCOS, and demonstrated effective blocking of GnRHR-AAb activity with epitope-mimicking retro-inverso peptide inhibitors. These proteolytically stable decoy peptides may have important therapeutic implications in subjects who harbor these autoantibodies.

Increased testosterone and proinflammatory cytokines in patients with polycystic ovary syndrome correlate with elevated GnRH receptor autoantibody activity assessed by a fluorescence resonance energy transfer-based bioassay

PURPOSE

The recently identified agonistic autoantibodies (AAb) to the gonadotropin-releasing hormone receptor (GnRHR) are a novel investigative and therapeutic target for polycystic ovary syndrome (PCOS). In this study, we used a new cell-based fluorescence resonance energy transfer (FRET) bioassay to analyze serum GnRHR-AAb activity and examine its relationship with testosterone and proinflammatory cytokines in patients with PCOS.

METHODS

Serum samples from 33 PCOS patients, 39 non-PCOS ovulatory infertile controls and 30 normal controls were tested for GnRHR-AAb activity and proinflammatory cytokines in a FRET-based bioassay and multiplex bead-based immunoassay, respectively. Correlation was analyzed using the Spearman's correlation test.

RESULTS

Serum GnRHR-AAb activity was significantly higher in the PCOS patients than for the ovulatory infertile (p < 0.05) and normal (p < 0.01) controls. GnRHR-AAb were positive in 39% of PCOS patients, 10% of ovulatory infertile controls, and 0% of normal controls. PCOS IgG-induced GnRHR activation was specifically blocked by the GnRHR antagonist cetrorelix. Serum levels of proinflammatory cytokines interleukin-2, interleukin-6, interferon-γ, and tumor necrosis factor-α were significantly increased in PCOS patients compared with ovulatory infertile and normal controls (p < 0.01). Correlation analysis demonstrated positive correlations of GnRHR-AAb activity with testosterone and proinflammatory cytokine levels in the PCOS group.

CONCLUSIONS

Elevated GnRHR-AAb activity, as assessed by a new FRET assay, is associated with increased testosterone and proinflammatory cytokines in PCOS, suggesting autoimmune activation of GnRHR may contribute to the pathogenesis of this common disorder.