preparation of letrozole filled mini pumps for the induction of polycystic ovarian syndrome in mice

Polycystic Ovary Syndrome Induction in Mice Through Controlled Letrozole Release 

Polycystic ovary syndrome (PCOS) is one of the most common conditions among women of reproductive age1. It affects up to 18% of women globally and is the leading cause of female infertility worldwide2,3. PCOS is characterized by a series of interrelated reproductive abnormalities, including disturbed gonadotropin secretion, chronic anovulation, increased androgen production, and polycystic ovarian morphology4. In addition to gynecological disorders, PCOS also increases the risk of cardiovascular diseases5,6. Despite decades of research, the etiology of PCOS remains unclear7,8.
To gain better insights into the pathogenesis of PCOS and develop novel therapies, the creation of animal models that closely mimic human physiology is of tremendous importance9. Currently reported rodent models of PCOS include those induced by treatments with testosterone, letrozole, and estradiol valerate, among others. Testosterone induces hyperandrogenemia and is more commonly used as a PCOS inducer in rats10. DHEA has been used to induce PCOS in rodents, increasing testosterone levels, LH/FSH (luteinizing hormone/follicle-stimulating hormone) ratios, and causing irregular estrous cycles11. Estradiol valerate (EV) is a long-acting estrogen, and studies using this method show that levels of sex steroid hormones and gonadotropins vary depending on the dose of EV administered12,13,14. Letrozole is a nonsteroidal aromatase inhibitor15. Letrozole treatment induces non-cyclic estrus, increases ovarian weight, body weight, enlarges adipocytes, maximizes follicle development, and elevates testosterone levels in rats16,17. Letrozole-treated mice exhibit increased numbers of sinus follicles and hemorrhagic cysts, as well as elevated concentrations of LH, FSH, estradiol, and progesterone18,19.
Currently, the main methods for letrozole-induced PCOS modeling involve oral administration and subcutaneous injection, both of which require repeated daily dosing20,21,22. These methods are time-consuming and labor-intensive, and the repetitive administration likely causes significant stress to the animals23. Although some studies use letrozole pellets24,25, these products need to be customized and are expensive. This report describes a technique for inducing PCOS in mice using mini-pumps. This method is simple, time-saving, and uses surgical tools and equipment that are readily available in most laboratories.

Author Spotlight: Investigating the Mechanisms and Inducing Models of Polycystic Ovary Syndrome

A Modified Technique for Inducing Polycystic Ovary Syndrome in Mice

Our research focuses primarily on the physiological and the pathological mechanisms related to polycystic ovary syndrome. Specifically, this research aims to develop a simple and efficient technique in inducing PCOS in mouse in order to better stimulate and study the physiological policies of PCOS, P-C-O-S. In 2023, academician Huang's team published a study in circulation that proposed a new mechanism involving chronic inflammation in the development of high-risk cardiovascular disease in patients with polycystic ovary syndrome.Our protocol offers a time-saving and flexible method to faithfully induce PCOS in mice, avoids repeated drug administration, and reduces the influence of non-experimental factors. Our laboratory will focus on investigating the mechanism behind the developmental origins of disease. We aim to uncover how adverse early life exposure contribute to the onset of metabolic, cardiovascular, and neurological disorders later in life.

Preparation of Letrozole Filled Mini Pumps for the Induction of Polycystic Ovarian Syndrome in Mice

To begin, place mini pumps on a clean, sterile countertop. With the thumb and forefinger, gently pinch the cap that matches the pump body and hold the pump body with the other hand. Use the thin tube attached to the cap to poke the filling port of the pump several times.Now take a needle that matches the pump and the one milliliter syringe. Attach the needle to the syringe tightly. Slowly draw up the final solution of letrozole into the syringe.Next, carefully pinch a mini pump with one hand so that it stands upright. With the other hand, insert the one milliliter syringe into the bottom of the pump. Slowly inject the letrozole solution into the pump.When the pump is full, withdraw the syringe. Carefully insert the cap into the pump body and tighten it. Wipe away any spillage that occurs.With the outlet of the filled pump facing outwards, immerse the pump into sterile saline in a prepared centrifuge tube. Cap the tube and place it on the tube rack. Place the tubes in a thermostat at 37 degrees Celsius for 48 hours.

preparation-letrozole-filled-mini-pumps-for-induction-polycystic

Research

JoVE Journal

Medicine

Polycystic ovary syndrome (PCOS) is one of the leading causes of infertility in women. Animal models are widely used to study the etiologic mechanisms of PCOS and for related drug development. Letrozole-induced mouse models replicate the metabolic and reproductive phenotypes of patients with PCOS. The traditional method of letrozole treatment in PCOS mice requires daily dosing over a certain period, which can be labor-intensive and cause significant stress to the mice. This study describes a simple and effective method for inducing PCOS in mice by implanting a controlled letrozole-releasing mini-pump. A mini-pump capable of stable, continuous release of a quantitative amount of letrozole was fabricated and implanted subcutaneously in mice under anesthesia. This study demonstrated that the mouse model successfully mimicked PCOS features after letrozole mini-pump implantation. The materials and equipment used in this study are readily available to most laboratories, requiring no special customization. Collectively, this article provides a unique, easy-to-perform method for inducing PCOS in mice.

This protocol introduces a technique for inducing polycystic ovary syndrome (PCOS) models in mice through controlled letrozole release using mini-pumps. Under adequate anesthesia, the mini-pump was implanted subcutaneously, and PCOS was successfully induced in the mice after a certain period of the mini-pump release.

Polycystic ovary syndrome (PCOS) is one of the leading causes of infertility in women. Animal models are widely used to study the etiologic mechanisms of ...

Induction of Polycystic Ovarian Syndrome in Mice Using Letrozole-Filled Mini Pumps

To begin, secure an anesthetized mouse in the prone position on an operating plate. Use forceps to pick up the skin at the midline of the back of the neck, favoring the skin on the hairless side. With a scalpel, laterally make a 0.5 centimeter long incision.Then, open the epidermis underneath the incision and access it with a hemostat to free the skin, making room for a mini pump. Next, use sterile forceps to take letrozole filled mini pump out of the saline with the open end of the pump facing downward. With a pair of forceps, clamp up one side of the skin incision.Then, push the pump into the subcutaneous space. Once the pump is inside, use your fingers to gently squeeze the pump as inward as possible. Then use 4-0 surgical sutures to suture the incision site.The Letrozole mini pump treated mice exhibited significantly elevated serum testosterone levels relative to the female control mice. Histological analysis of the mice ovaries showed that the treated mice had a significant reduction in the corpora lutea number. They also showed significant estrous cyclicity and were heavier than the control mice.The treated mice developed glucose intolerance and had higher changes in serum lipid profiles.