Human Internal Mammary Artery (IMA) Transplantation and Stenting: A Human Model to Study the Development of In-Stent Restenosis
May 9th, 2012
This video shows a model to study the development of intimal hyperplasia after stent deployment using a human vessel (IMA) in an immunodeficient rat model.
The overall goal of this procedure is to study the development of intimal hyperplasia in a humanized model. This is accomplished by first denuding, a section of human mammary artery or IMA, using a two French fogerty catheter. Next, a stent is inserted into the IMA.
Then a segment of rat abdominal aorta is replaced with a stented IMA. Finally, the wound is sutured and the animal is allowed to recover the endothelial damage due to the invasive procedure of balloon dilatation and stenting results in inflammation and the production of inflammatory cytokines. This leads to the proliferation of smooth muscle cells, which progressively occlude the vessel lumen resulting in stenosis.
Ultimately, results can be obtained that show the proliferation of human smooth muscle cells through immunofluorescence confocal microscopy. Today we will show you a model for the assessment of wrist stenosis in human arteries in a red host. The advantage of this model of existing techniques like the abdominal wet aortic standing, is that we can assess human stents in human tissue.
We first had the idea for this method when we were aiming to find a translational in vivo model for vascular remodeling. To prepare the IMA begin by using a two French Fogarty arterial embolectomy catheter to denude the arterial endothelium by moving the catheter into the vessel to ensure endothelial damage. Insert a human stent of eight millimeters in length and 2.5 to three millimeters in diameter into the vessel.
Using the appropriate balloon pressure, deploy the stent to achieve the desired diameter. Store the stented IMA on ice at four degrees Celsius in RPMI and Heparin until transplantation. After anesthetizing, a rat with isoflurane, shave the abdominal hair, place a face mask over its nose and mouth to maintain 2%anesthesia using provo iodine, disinfect the abdominal area widely and follow it with 80%ethanol.
Repeat these steps twice. Pinch the hind feet to be sure that the rat is sufficiently sedated. Next, perform an upper median laparotomy to expose the infrarenal abdominal aorta.
Then place the intestines in a saline moisturized glove and fold the glove around the intestines to prevent loss of moisture Under a surgical microscope, dissect the aorta from the infrarenal region to the bifurcation, taking care not to cause damage on the branches of the vessels. To stop aortic blood flow, use micro clamps to first clamp the proximal end, then the distal end. Remove an approximately 0.5 to 0.7 millimeter aortic segment and flush the remaining aorta with 200 units of heparin.
Next, shorten the stented IMA to an adequate length and position it into the aortic gap. Then using running sutures, connect the IMA to the recipient aorta. Carefully open first the coddle and afterwards the cranial clamp.
There should be a visible pulse in the transplanted IMA and at the distal end of the aorta. Place the intestines back into the abdomen and flush it with prewarm sterile saline. Use six aut proline running sutures to close the muscle layer of the abdominal wall, followed by the skin layer.
While the rat is still under anesthesia subcutaneously. Inject four to five milligrams per kilogram of carprofen. Monitor the animal daily until removal of the IMA to identify the origin of proliferation.
Human IMA was stably transduced to overexpress GFP in the vessel. Histological sections were stained with antibodies against GFP shown here in green and human smooth muscle actin or SMA seen in red. The cell nuclei are in blue.
Shown here is emerged confocal image showing the origin of proliferated cells. This 3D video shows the colocalization of SMA in red and GFP in green Following surgery. Other methods like histopathology and the confocal immunofluorescence micro can be performed in order to answer the questions like luminal obliteration, morphology, and the cellularity.
This method is a promising model for translational research. Thank you for watching and good luck with your experiments.I.
View the full transcript and gain access to thousands of scientific videos
Overview
This video demonstrates a model for studying intimal hyperplasia development after stent deployment using a human vessel (IMA) in an immunodeficient rat model. The procedure involves denuding the IMA, stent insertion, and transplantation into the rat aorta.
Key Study Components
Area of Science
- Vascular biology
- Translational research
- Cardiovascular pathology
Background
- Intimal hyperplasia is a common complication after stent placement.
- Humanized models can provide insights into vascular remodeling.
- Existing models have limitations in assessing human stents in human tissue.
- This study aims to create a more relevant in vivo model.
Purpose of Study
- To develop a model for assessing intimal hyperplasia in human arteries.
- To evaluate the effects of stenting on human smooth muscle cell proliferation.
- To utilize a humanized rat model for translational research.
Methods Used
- Denuding the IMA using a Fogarty catheter.
- Inserting a stent into the IMA and preparing it for transplantation.
- Performing a laparotomy to expose the rat aorta for IMA implantation.
- Monitoring the rat post-surgery for signs of proliferation and recovery.
Main Results
- Successful transplantation of the stented IMA into the rat aorta.
- Proliferation of human smooth muscle cells observed via immunofluorescence.
- Visible pulse in the transplanted IMA indicating successful blood flow.
- Histological analysis confirmed the presence of proliferated cells.
Conclusions
- This model provides a promising approach for studying vascular remodeling.
- It allows for the assessment of human stents in a relevant biological context.
- Further research can utilize this model to explore therapeutic interventions.
Frequently Asked Questions
Executive Industry Relevance
This humanized model addresses a critical translational gap in cardiovascular device development by enabling direct assessment of human vascular responses to stenting in vivo. It supports mechanistic de-risking of stent designs and materials by providing human-relevant data on intimal hyperplasia formation, a key predictor of long-term device performance. The model enhances predictive confidence in preclinical evaluation, informing go/no-go decisions earlier in the discovery pipeline and reducing late-stage biological risk in stent development programs.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses related to smooth muscle cell proliferation and vascular remodeling pathways in human tissue.
- Operational Value: Provides a reproducible system for functional target validation of anti-proliferative compounds using human-derived cells.
- Scientific Value: Supports predictive confidence by demonstrating human-specific cellular origins of restenosis, improving target selection for mechanistic de-risking.
Screening & Assay Development
- Scientific Value: Prepares validated human vascular systems for downstream compound screening with quantifiable immunofluorescence readouts.
- Operational Value: Ensures assay standardization and reproducibility through controlled stent deployment and transplantation procedures.
- Scientific Value: Enables reliable compound evaluation by linking stent exposure to measurable human smooth muscle cell proliferation via GFP and SMA colocalization.
Translational & Preclinical Research
- Scientific Value: Maintains disease relevance by modeling human intimal hyperplasia, a direct precursor to clinical stent failure.
- Operational Value: Ensures continuity from discovery through preclinical validation using a living organism with human tissue engraftment.
- Strategic Value: Supports risk-adjusted advancement decisions by providing human-derived proliferation data before costly clinical trials.
Pipeline & Workflow Integration
The model fits within the discovery continuum from target validation through lead identification to preclinical assessment, specifically enabling evaluation of stent-induced biological responses in a human context.
- Discovery Biology: Supports hypothesis testing of stent-material interactions and pathway clarification of inflammatory cascades leading to stenosis.
- Screening: Delivers assay readiness through standardized IMA preparation, stent deployment, and quantitative confocal imaging outputs.
- Analytics: Provides measurements of human smooth muscle cell proliferation and luminal obliteration to compare stent performance across conditions.
- Translational Research: Connects to preclinical continuity by using immunodeficient rats to sustain human tissue viability and monitor proliferative responses over time.
- Enterprise Reuse: Functions as a reusable platform for iterative stent design testing rather than a single-use technique.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in target validation by reducing mechanistic ambiguity around human-specific restenosis drivers.
- Operational Value: Enhances standardization and scalability through defined catheter-based denudation, stenting, and microsurgical transplantation steps.
- Strategic Value: Improves go/no-go decision quality and capital efficiency by identifying biologically active stent designs earlier in development.
- Portfolio Impact: Enables risk-adjusted prioritization of stent candidates based on human-derived proliferation data, reducing late-stage failure risk.
Implementation Considerations
- Requires expertise in vascular microsurgery, immunofluorescence staining, and confocal microscopy for accurate proliferation tracking.
- Dependent on access to human internal mammary arteries, stent deployment systems, and immunodeficient rat models for engraftment studies.
- Necessitates cross-team standardization between vascular biology, pathology, and imaging groups to ensure consistent tissue preparation and readout interpretation.
- Involves adaptation considerations when applying the model to different vessel types or stent geometries beyond the IMA and aortic gap.
- Limited by the need for specialized surgical facilities and postoperative monitoring to maintain graft viability and detect proliferative endpoints.
