Establishment of a Simple and Effective Rat Model for Intraoperative Parathyroid Gland Imaging
August 17th, 2022
To date, the development of parathyroid gland (PG) identification methods is limited by the lack of animal models in preclinical research. Here, we establish a simple and effective rat model for intraoperative PG imaging and evaluate its effectiveness by using iron oxide nanoparticles as a novel PG contrast agent.
Parathyroid gland is a small organ with very important functions. Our protocol can be used for developing new PG identification technologies which can help surgeons to protect it during the thyroidectomy for thyroid cancer. The main advantage of this model is that it can observe a clear difference between the thyroid and PGs through the negative imaging of IONP.
In addition, the cost and operational difficulty are considerably lower for this rat model than for large animal models. To begin, place a prewarmed heating pad on the surgical table in order to sustain the animal's body temperature during the surgery, and then transfer the anesthetized rat down to a surgical drape placed on the operation table. Using rubber bands, fix the rat's limbs to the operation table and place a cylindrical pillow made of drape under the rat's shoulder to lean its head back, completely exposing the neck area, then apply depilatory cream to the neck area, up to the submandibular space, down to the xiphoid process, and on both sides to the outside of the sternocleidomastoid muscle.
After three minutes, gently wipe the hair and depilatory cream with a tissue. Next, using an iodophor cotton ball, sterilize the middle of the neck and surrounding area. from which hair is removed.
Cover the animal with a surgical drape, keeping the hole aligned with disinfected area. Using the scalpel, make approximately a five-centimeter longitudinal incision in the anterior midline of the rat's neck. Lift the skin along both sides of the incision and using scissors, longitudinally cut along the linea alba cervicalis.
Use forceps to separate the sternohyoid and sternothyroid muscle. Clamp the separated muscles in front of the neck using vascular forceps and pull the clamped tissue outside. Using the needle, pass the suture through the clamped tissue.
Make a knot and fix the suture to the surgical drape of the operation table. Locate the thyroid cartilage based on its shield shape and cricoid cartilage based on its ring shape as the upper boundary in the operation area, then locate the trachea based on its tubular cartilage ring shape in the front and middle of the neck as the lower boundary in the operation area. Locate the thyroid gland, a red butterfly-shaped gland on the opposite side of the trachea between the upper and lower boundaries.
Next, locate two parathyroid glands in a fusiform shape that are reddish, but lighter than the surrounding thyroid gland with a certain boundary on the upper and outer sides of the thyroid gland. Take a frontal photograph of the parathyroid glands with the trachea, thyroid, and larynx. Dissect the back of the esophagus and using a retractor, expose the right side of the parathyroid glands.
Take a right-side photograph of the parathyroid glands with the thyroid gland and trachea, and similarly expose and capture the left side of the glands. Use an insulin syringe to locally inject 10 microliters of black iron oxide nanoparticles suspension into the center of the thyroid gland, and gently press the injection site with gauze for five seconds, then observe the rapid diffusion of the black iron oxide nanoparticles within the thyroid glands, but not the parathyroid glands, as it negatively stains the parathyroid glands and differentiates them from the surrounding thyroid. Capture the front, left, and right-side photographs of the negatively stained parathyroid glands together with the trachea, thyroid gland, and larynx.
After injection, the contrast agent, black iron oxide nanoparticles, readily diffuse within the thyroid gland and stain it black, but cannot infiltrate the parathyroid gland due to their high tissue density. Histological analysis of black iron oxide nanoparticles injected-thyroid gland revealed that the parathyroid glands are enriched with closely aligned chief cells, whereas the thyroid gland features many loose lumens indicating much lower tissue density. Two important things should be remembered in this procedure.
First, the posture of the rat. We recommended to lean ears and head back, completely exposing the neck area. Second, when we inject the IONPs, we should be use fine-ensuring needle because the thyroid surface is full of blood vessels.
This procedure can also be performed by autofluorescence imaging of the PG, which is non-invasive, provides real-time information, and does not use dye as a contrast agent, but the autofluorescence signal is weak and the imaging efficiency is also poor. Other researchers can use this simple and effective rat model to develop and evaluate new PG identification technologies and products instead of using more complicated and expensive large animals such as dogs and pigs.
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Overview
This study establishes a rat model for intraoperative imaging of the parathyroid gland (PG) using iron oxide nanoparticles as a contrast agent. The model aims to improve PG identification during thyroid surgeries, enhancing surgical outcomes.
Key Study Components
Area of Science
- Neuroscience
- Biology
- Surgical Techniques
Background
- The parathyroid gland plays a crucial role in calcium homeostasis.
- Current PG identification methods are limited by the lack of suitable animal models.
- Improving PG visibility during thyroidectomy is essential for preserving gland function.
- Iron oxide nanoparticles (IONP) offer a novel approach for enhancing imaging contrast.
Purpose of Study
- To develop a cost-effective rat model for PG imaging.
- To evaluate the effectiveness of IONP as a contrast agent.
- To facilitate better surgical techniques for thyroid cancer treatment.
Methods Used
- Preparation of a rat model for surgery.
- Application of IONP for imaging contrast.
- Intraoperative imaging techniques to differentiate PG from thyroid tissue.
- Assessment of the model's effectiveness in a surgical setting.
Main Results
- The rat model successfully demonstrated clear imaging of PGs.
- IONP provided significant contrast between PG and surrounding tissues.
- The model proved to be less costly and easier to operate than larger animal models.
- Enhanced visibility of PGs can lead to improved surgical outcomes.
Conclusions
- The established rat model is effective for intraoperative PG imaging.
- Using IONP as a contrast agent significantly aids in PG identification.
- This approach may enhance surgical techniques and patient safety during thyroidectomies.
Frequently Asked Questions
Executive Industry Relevance
Reliable intraoperative identification of the parathyroid gland (PG) is a critical challenge in endocrine surgery, with direct implications for surgical safety and post-operative outcomes. The establishment of a simple, cost-effective rat model using iron oxide nanoparticles (IONPs) as a contrast agent addresses a major preclinical bottleneck for developing and validating PG imaging technologies. This model enables translational research teams to accelerate the evaluation of novel PG identification tools, supporting predictive confidence and de-risking at the discovery and preclinical interface.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables systematic evaluation of PG imaging agents in a controlled, reproducible animal model.
- Supports mechanistic de-risking by clarifying tissue-specific contrast agent distribution.
- Facilitates functional validation of imaging targets relevant to surgical guidance.
Screening & Assay Development
- Provides a standardized platform for quantitative assessment of imaging contrast and tissue selectivity.
- Enables reproducible comparison of candidate agents or imaging modalities for PG identification.
- Supports assay development for preclinical screening of novel contrast agents.
Translational & Preclinical Research
- Aligns preclinical imaging outputs with surgical workflow requirements for translational continuity.
- Reduces reliance on large animal models, improving scalability and cost-efficiency for early-stage validation.
- Facilitates risk-adjusted advancement of imaging technologies toward clinical evaluation.
Pipeline & Workflow Integration
This rat model positions PG imaging agent evaluation at the intersection of early discovery, lead identification, and preclinical validation, enabling iterative optimization before large animal or clinical studies.
- Discovery Biology: Supports hypothesis testing for tissue-specific imaging agent uptake and distribution.
- Screening: Provides quantitative, reproducible readouts for contrast agent performance.
- Analytics: Enables direct measurement of imaging contrast and tissue differentiation.
- Translational Research: Bridges discovery-stage findings with surgical application requirements.
- Enterprise Reuse: Offers a reusable, low-cost platform for ongoing imaging technology development.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in imaging agent performance and tissue selectivity.
- Operational Value: Standardizes preclinical evaluation, reducing cost and complexity versus large animal models.
- Strategic Value: Accelerates go/no-go decisions for imaging agent advancement and portfolio triage.
- Portfolio Impact: Enables risk-adjusted prioritization of imaging technologies for surgical guidance.
Implementation Considerations
- Requires expertise in small animal surgery and imaging agent administration.
- Needs access to histological and imaging analysis infrastructure for quantitative assessment.
- Demands cross-team standardization of injection and imaging protocols for reproducibility.
- Adaptable to evaluation of both nanoparticle-based and autofluorescence imaging agents.
- Limited by differences in tissue architecture between rat and human PGs, requiring further validation in higher-order models.
Biopharma FAQs
Chapters in this video
0:05
Introduction
0:53
Animal Preparation
2:05
Incision, Dissection of the Subcutaneous Tissue, and Anterior Neck Muscle Fixation
2:56
Thyroid Gland Localization and Visual Identification of the Parathyroid Gland (PGs)
4:18
Black Iron Oxide Nanoparticles (IONPs) Injection and PGs Identification
5:09
Results: Effects of IONP Injection and PGs Identification Post-Injection
5:51
Conclusion
