A Rabbit Venous Interposition Model Mimicking Revascularization Surgery using Vein Grafts to Assess Intimal Hyperplasia under Arterial Blood Pressure
May 15th, 2020
The present protocol aims to experimentally create venous intimal hyperplasia by subjecting veins to arterial blood pressure for developing strategies to attenuate venous intimal hyperplasia following revascularization surgery using vein grafts.
Our protocol provides an easy, cost-effective, reproducible and clinical relevant model for researchers in the field of venous intimal hyperplasia. Our protocol is economically, clinically, and technically balanced. Therefore, it is highly recommended for researchers who want to apply their in vitro outcomes to an in vivo setting.
We believe that our protocol can be applied to a larger animal model for the development of new treatment strategies in ischemic heart and lower extremity diseases. Our protocol is mainly relevant to the field of cardiovascular surgery. However, it may also be used to address degenerative changes in arteriovenous fistulas in patients with end stage renal disease.
After local anesthetic, and prophylactic antibiotic analgesic administration, disinfect the surgical site with 10%povidone-iodine. And make a 50 to 60 millimeter incision with a surgical scalpel in the cervical region of the anesthetized male Japanese white rabbit. Bluntly dissect the subcutaneous tissues and fascia to expose a 20 to 30 millimeter segment of the jugular vein.
And use 4-0 silk sutures to ligate all of the branches of the exposed vein. Place a 2-0 silk suture around the internal and external jugular veins and make a one millimeter incision in the venous wall of the distal side of the vein. Insert a 2-French balloon catheter from the cut toward the proximal side of the vein.
And ligate the 2-0 silk suture at the distal sites of the jugular veins. Inflate the balloon with 200 microliters of air. And use the balloon to denude the intima of the vein three times for endothelial exfoliation.
After the third passage, ligate the proximal end of the vein and cut the vein at the distal site. Then insert a 20 gauge intravenous catheter into the harvested vein from the distal to the proximal direction, and cut the vein at the proximal site. To interpose the carotid artery with the harvest jugular vein, expose a 20 to 30 millimeter segment of the ipsilateral carotid artery.
And separate the artery carefully from the nearby vein and nerve. Ligate all the branches of the exposed vein with 4-0 silk suture. And intravenously administer 200 International Units per kilogram of heparin sodium.
Clamp the proximal and distal ends of the artery with surgical rubber clamps. And cut the artery between the clamps. Inject normal saline into the incised carotid artery proximally and distally to distend the artery.
And place the harvest vein near the artery to anastomose the vessel in a reversed end-to-end fashion. To anastomose the proximal end of the vein to the distal end of the artery, place two anchor stitches of 8-0 polypropylene at the site and the opposite site. Add stitches the upper side of the anastomosis line between the anchor stitches.
Flip the artery and the vein graft upside down. And add stitches on the remaining part of the anastomosis line. Next, remove the intravenous catheter from the vein and clamp the vein graft proximally.
Declamp the carotid artery distally. And observe whether the vein graft expands gradually. Using 8-0 polypropylene interrupted sutures, anastomose the distal end of the vein to the proximal end of the artery.
And declamp the artery to check for bleeding from the anastomosis sites. Finally, ligate the internal carotid artery with a 4-0 silk suture to simulate a poor runoff condition and to facilitate intimal hyperplasia. Then clean the wound with saline.
Close the incision with 3-0 polyglactin 910 in layers. And allow the rabbit to fully recover with monitoring before returning the animal to its home cage. In this representative image, a successful intimal hyperplasia at 2 weeks after venous interposition surgery can be observed.
Here, the therapeutic effects of microRNA-145 loaded poly(lactic-co-glycolic acid)nanoparticles on the intimal hyperplasia morphology can be observed. Indeed, treatment with microRNAs loaded with poly(lactic-co-glycolic acid)nanoparticles results in a significant attenuation of intimal hyperplasia. In addition, immunostaining for Ki-67, a cell proliferative marker, reveals fewer Ki-67-positive cells within the microRNA-145 treated group indicating a phenotype change in the vascular smooth muscle cells from the immature proliferative state to the mature contractile state.
The main goal of our protocol is to achieve patency of the implanted graft. It is also important to confirm that the graft expands after declamping the carotid artery.
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Overview
This protocol provides a cost-effective and reproducible model for studying venous intimal hyperplasia by exposing veins to arterial blood pressure. It is relevant for researchers aiming to develop treatment strategies for conditions related to ischemic heart and lower extremity diseases.
Key Study Components
Area of Science
- Cardiovascular surgery
- Venous intimal hyperplasia
- Revascularization surgery
Background
- Venous intimal hyperplasia is a common complication following vein graft procedures.
- Understanding the mechanisms behind this condition is crucial for improving surgical outcomes.
- Current models may not adequately replicate the clinical scenario.
- This protocol aims to fill that gap by providing a relevant experimental model.
Purpose of Study
- To create a model of venous intimal hyperplasia.
- To develop strategies to mitigate this condition post-surgery.
- To facilitate the translation of in vitro findings to in vivo applications.
Methods Used
- Application of arterial blood pressure to veins.
- Assessment of intimal hyperplasia development.
- Evaluation of potential treatment strategies.
- Use of a larger animal model for further research.
Main Results
- The protocol is economically and clinically balanced.
- It allows for reproducible results relevant to human conditions.
- Potential applications in addressing degenerative changes in arteriovenous fistulas.
- Encourages further research into ischemic diseases.
Conclusions
- This model can significantly aid in understanding venous intimal hyperplasia.
- It is a valuable tool for researchers in cardiovascular surgery.
- Future studies may lead to improved treatment strategies for affected patients.
Frequently Asked Questions
Executive Industry Relevance
This model enables preclinical evaluation of therapeutic strategies targeting venous intimal hyperplasia, a key failure mode in vascular graft revascularization. By replicating arterial pressure exposure in a surgically accessible venous interposition system, it supports mechanistic de-risking of anti-proliferative interventions before costly large-animal or clinical testing. The platform enhances predictive confidence in target validation for vascular smooth muscle phenotype modulation, directly informing go/no-go decisions in cardiovascular therapeutic development.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses targeting vascular smooth muscle cell phenotype switching from proliferative to contractile state.
- Operational Value: Provides a reproducible in vivo system to validate target engagement and functional impact of molecular interventions like miR-145 delivery.
Screening & Assay Development
- Scientific Value: Generates quantifiable histopathological endpoints (intimal thickness, Ki-67 positivity) for dose-response assessment of candidate therapeutics.
- Operational Value: Supports standardization of venous graft preparation and arterial coupling for consistent phenotypic readouts across studies.
Translational & Preclinical Research
- Scientific Value: Bridges in vitro findings (e.g., miR-145 effects on VSMCs) to physiologically relevant arterial pressure conditions in vivo.
- Operational Value: Facilitates longitudinal monitoring of graft patency and hyperplasia progression, enabling longitudinal efficacy studies.
Pipeline & Workflow Integration
The model fits within the cardiovascular discovery continuum, supporting target validation after in vitro screening and prior to preclinical efficacy testing in larger models or clinical translation.
- Discovery Biology: Tests mechanistic hypotheses about vascular remodeling pathways under pathophysiological mechanical stress.
- Screening: Delivers quantitative histological and immunohistochemical outputs to rank-order therapeutic candidates.
- Analytics: Enables morphometric and proliferative index analysis (e.g., intimal hyperplasia area, Ki-67+) to compare treatment effects.
- Translational Research: Provides disease-relevant venous graft environment to assess continuity of mechanism from cell culture to tissue-level outcome.
- Enterprise Reuse: Establishes a standardized surgical platform adaptable to multiple therapeutic modalities ( nucleic acids, drugs, biologics) for vascular graft improvement.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in vascular graft failure by isolating intimal hyperplasia as a pressure-dependent process.
- Operational Value: Offers a cost-effective, reproducible model with limited invasiveness, supporting longitudinal studies and reduced animal use.
- Strategic Value: Improves go/no-go criteria by predicting clinical graft failure risk based on hyperplasia attenuation efficacy.
- Portfolio Impact: Enables risk-adjusted prioritization of vascular therapeutic candidates targeting smooth muscle phenotype modulation.
Implementation Considerations
- Requires expertise in microvascular surgical techniques and venous/arterial anastomosis in small mammals.
- Dependent on access to surgical equipment (microsurgical instruments, sutures, balloon catheters, heparin) and postoperative monitoring facilities.
- Necessitates standardized protocols for venous harvest, intimal denusion, and arterial coupling to ensure model reproducibility.
- Adaptation to larger animal models may require scaling of vessel size, suture gauge, and anticoagulant dosing while preserving arterial pressure exposure.
- Outcome assessment depends on histological processing and immunohistochemical staining capabilities for endpoints like intimal thickness and Ki-67.
