Custom tissue engineered aneurysm models with varying neck size and height for early stage in vitro testing of flow diverters

Evaluation of vessel injury after simulated catheter use in an endothelialized silicone model of the intracranial arteries

PURPOSE

Neurothrombectomy catheters can disrupt or injure the vessel wall. This potential injury is often studied in animal or cadaver models, but prior work suggests that endothelialized silicone models may be an option for early in vitro assessment. The purpose of this work was to create a complex, clinically-relevant endothelialized neurovascular silicone model, and to determine the utility of the model for evaluating vessel injury due to catheter simulated use.

METHODS

Models of the ICA and MCA were fabricated out of silicone, sterilized, coated with fibronectin, placed in bioreactors, and endothelialized with HUVECs. These silicone vessels were maintained under flow for 3 and 7 days, and cellular linings were assessed. Subsequently, 24 silicone vessels were created and treated with neurovascular catheters. Vessels were accessed with a guidewire, microcatheter, and/or aspiration catheter, either once (1-pass) or three times (3-pass). Vessels were then fixed, and injury was evaluated through quantitative image analysis and a visual scoring system.

RESULTS

Complex silicone models were successfully endothelialized and maintained with consistent cell linings. The transparent silicone permitted catheter simulated use without fluoroscopy, and injury to the vessel wall was observed and successfully imaged and characterized. Vessels subjected to 3-passes exhibited more injury than 1-pass, and injury increased with the number and size of devices. These results illustrated expected trends and support use of these models for early assessment of vessel injury.

CONCLUSION

Complex silicone neurovascular models can be endothelialized and used in vitro to assess and compare injury due to the use of neurovascular catheters.

Cellular responses to flow diverters in a tissue-engineered aneurysm model

BACKGROUND

Notwithstanding the widespread implementation of flow diverters (FDs) in the treatment of intracranial aneurysms, the exact mechanism of action of these devices remains elusive. We aimed to advance the understanding of cellular responses to FD implantation using a 3D tissue-engineered in vitro aneurysm model.

METHODS

Aneurysm-like blood vessel mimics (aBVMs) were constructed by electrospinning polycaprolactone nanofibers onto desired aneurysm-like geometries. aBVMs were seeded with human aortic smooth muscle cells (SMCs) followed by human aortic endothelial cells (ECs). FDs were then deployed in the parent vessel of aBVMs covering the aneurysm neck and were cultivated for 7, 14, or 28 days (n=3 for each time point). The EC and SMC coverage in the neck was measured semi-quantitatively.

RESULTS

At day 7, the device segment in contact with the parent vessel was partially endothelialized. Also, the majority of device struts, but not pores, at the parent vessel and neck interface were partially covered with ECs and SMCs, while device struts in the middle of the neck lacked cell coverage. At 14 days, histology verified a neointimal-like lining had formed, partially covering both the struts and pores in the center of the neck. At 28 days, the majority of the neck was covered with a translucent neointimal-like layer. A higher degree of cellular coverage was seen on the struts and pores at the neck at 28 days compared with both 7 and 14 days.

CONCLUSION

aBVMs can be a valuable alternative tool for evaluating the healing mechanisms of endovascular aneurysm devices.

Endothelialized silicone aneurysm models for in vitro evaluation of flow diverters

Objective

The goal of this work was to endothelialize silicone aneurysm tubes for use as in vitro models for evaluating endothelial cell interactions with neurovascular devices. The first objective was to establish consistent and confluent endothelial cell linings and to evaluate the silicone vessels over time. The second objective was to use these silicone vessels for flow diverter implantation and assessment.

Methods

Silicone aneurysm tubes were coated with fibronectin and placed into individual bioreactor systems. Human umbilical vein endothelial cells were deposited within tubes to create silicone vessels, then cultivated on a peristaltic pump and harvested at 2, 5, 7, or 10 days to evaluate the endothelial cell lining. A subset of silicone aneurysm vessels was used for flow diverter implantation, and evaluated for cell coverage over device struts at 3 or 7 days after deployment.

Results

Silicone vessels maintained confluent, PECAM-1 (platelet endothelial cell adhesion molecule 1) positive endothelial cell linings over time. These vessels facilitated and withstood flow diverter implantation, with robust cell linings disclosed after device deployment. Additionally, the endothelial cells responded to implanted devices through coverage of the flow diverter struts with increased cell coverage over the aneurysm seen at 7 days after deployment as compared with 3 days.

Conclusions

Silicone aneurysm models can be endothelialized and successfully maintained in vitro over time. Furthermore, these silicone vessels can be used for flow diverter implantation and assessment.