Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent <em>In Vivo </em>Monitoring

Abstract

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large animal model. A step by-step protocol for inter-positional placement of the TEV and real-time digital assessment of the TEV and native carotid arteries is described here. In vivo monitoring is made possible by the implantation of flow probes, catheters and ultrasonic crystals (capable of recording dynamic diameter changes of implanted TEVs and native carotid arteries) at the time of surgery. Once implanted, researchers can calculate arterial blood flow patterns, invasive blood pressure and artery diameter yielding parameters such as pulse wave velocity, augmentation index, pulse pressures and compliance. Data acquisition is accomplished using a single computer program for analysis throughout the duration of the experiment. Such invaluable data provides insight into TEV matrix remodeling, its resemblance to native/sham controls and overall TEV performance in vivo.

Implantation of VEGF‐functionalized cell‐free vascular grafts: regenerative and immunological response

“…Using SIS with immobilized heparin and VEGF, we developed cell‐free off‐the‐shelf vascular grafts with submillimeter inner diameters (850–900 µm) that were implanted into the arterial system of a mouse. Similar to our previous study with an ovine animal model, grafts demonstrated host cell integration and a confluent endothelium within the lumen (34, 36). Cell‐free vascular grafts of such small sizes are a continuing challenge for the field of tissue engineering.…”

“…One study implanted a heparin‐functionalized elastomer in a rat model that proved to be effective in promoting endothelialization (21). However, heparin‐functionalized grafts occluded within the first few hours after implantation into the carotid artery of sheep (34, 36). On the other hand, in the current study we found no difference in graft patency between heparin‐only (SH) and heparin/VEGF (SHV) grafts using the same biomaterial and immobilization strategy, despite the much smaller graft diameter.…”

“…SIS conduits were further processed using a protocol that we previously published (34, 36). Briefly, the grafts were placed in a solution of 5‐mg/ml heparin (low MW; MilliporeSigma), 20‐mM 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide, and 10 mM N‐ hydroxysuccinimide in 50 mM 2‐ethanesulfonic acid buffer (pH 4.5).…”

Successful endothelialization and remodeling of a cell-free small-diameter arterial graft in a large animal model

“…After excising ≈ 5cm in-situ of native carotid in order to retain longitudinal tension, each A-TEV (4cm in length) was placed end to end in the carotid artery using interrupted suture technique. Following the unclamping of the artery and restoration of normal blood flow through the TEV, instruments were placed onto the newly sutured vessel allowing real-time monitoring of arterial dynamics during recovery as described recently[37]. A 4mm doppler flow probe (Transonic Systems Inc., Ithaca NY) was placed proximal to the TEV, 1mm sonomicrometry crystals (Sonometrics Inc., London, Canada), were placed laterally opposite to each other at the midpoint of the A-TEV.…”

“…At indicated time points, implanted probes were connected to corresponding transducers to enable data acquisition using Sonolab DS3 (Sonolab version 1.0.0.60, Sonometrics Inc., London, Canada) as previously described[37]. Following transducer calibration and establishment of stable connections, 30sec–1min of data were recorded.…”