Ultrasonography in Experimental Reproductive Investigations on Rats

Summary

This manuscript describes the utility of ultrasound performed on female rats to design experimental models for reproductive and gynecological investigation. A step-by-step explanation of how to perform ultrasonographic evaluation is shown.

Abstract

With the development of assisted reproductive technology and the ethical limitations of research on humans, rat animal models have been widely used in reproductive medicine. In the past, the study of reproductive system development in rodents has been based on one-time histological examination of excised tissues. Recently, with the development of high-resolution transabdominal ultrasound, high-quality sonography can now be performed to evaluate the reproductive organs of rats, allowing a new method for studying the reproductive system. Images were obtained using a high-resolution ultrasonographic system. Gynecological ultrasonography was performed on 28 eight-week-old non-pregnant rats and 5 pregnant Sprague-Dawley rats. We describe how to recognize organs of the reproductive system and associated structures in typical views during different phases of the estrus cycle. Color flow Doppler was used to measure uterine artery blood flow and evaluate uterine blood flow pattern changes during different stages of pregnancy. We have demonstrated that ultrasound exploration is a useful method for evaluating changes in internal reproductive organs. Its use raises the possibility of conducting additional experiments, including medical or surgical procedures, and provides the ability to monitor sonographic changes to internal organs without sacrificing animals.

Introduction

Rat animal models have been widely used in reproductive medicine, including in embryo and ovarian transplantation^1,2. However, in the past, the study of reproductive system development in rodents has been based on one-time histological examination of excised tissues, and the longitudinal study of day-to-day reproductive organ changes has not been possible in rats³. Ultrasound has been widely used in assisted reproductive technology in humans for over 30 years, but this valuable technology has only been applied to rats recently.

Our objective was to establish ....

Protocol

This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health and in accordance with the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines. The protocol received a license for animal experimentation complying with Directive 2010/63/EU with the authorization number A13170404 (Anexo 1). All experiments were performed in a European Union-certified laboratory following national guidelines for the ethical care of animals (RD 53/2013, EU Directive 63/2010). The protocol was approved by the Committee on the Ethics of Animal Experiments of the University of....

Results

There were no significant differences in antero-posterior uterine horn diameters or in the thickness of the endometrium between the two sides of the uterine horn (Table 1). Compared with the group 2, the mean endometrial thickness in the group 1 was thicker, but no significant differences (P>0.05) were found between the two groups (Figure 3). Nevertheless, we found fluid inside the uterus (in 8 out of 28 rats) near the estrus cycle associated with changes in endometrium m.......

Discussion

Due to the procedural modifications and troubleshooting that was required in this study, despite our aim of identifying all the phases of the estrus cycle in rats using ultrasound, we were unable to find any significant differences. We hypothesize that these difficulties may be because the estrus cycle only lasts a few days in rats, unlike the cycle in women. We are sure that all measurements were done at exactly the right time to determine any differences. Therefore, we regrouped the estrus cycle phases into only two ph.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Vevo3100 high-resolution in vivo micro-imaging system*	Visual Sonics, inc.		www.visualsonics.com/products
Vevo integrated rail system including physiological monitoring unit.	Visual Sonics, inc.		www.visualsonics.com/products
MX400 Transducter	Visual Sonics, inc.		www.visualsonics.com/products
Vevo Lab Software	Visual Sonics, inc.		www.visualsonics.com/products
HSD: Sprague Dawley SD	Envigo, inc.		Rat strain
Lubricating Gel	General Supply
CIBERTEC CA-EAC20 Anesthesia Trolley System	Cibertec S.A		Anesthesia Machine
Ecogel 100 ultrasound gel	Eco-Med Pharmaceuticals Inc.
Hair removal lotion (Nair)	General Supply
Isoflurane	Esteve Veterinaria		Inhalatory anesthesia
* Required software is Vevo software including B-Mode application, pulse wave Doppler application, and vascular strain analysis tools package.