Society For Clinical Vascular Surgery

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Interposition aortic grafting in the murine model using human umbilical cord artery
Herbert Dardik, MD, Thomas Bernik, MD, Thomas Hoffman, BA, Robert Pergolizzi, PhD.
Englewood Hospital & Med. Center, Englewood, NJ, USA.

OBJECTIVES: Aortic surgery in the murine model is a challenging technical procedure but can be accomplished with combined surgical expertise, magnification and extreme patience. We undertook this challenge to assess feasibility, economic savings, and evaluation of various preparations of graft material and to study long-term morphology and host interactions.
METHODS: Aortic interposition grafts consisting of human umbilical cord arteries prepared with 2.5 or 4.0 % gluteraldehyde were placed in 16 Sprague-Dawley rats weighing 350-400 grams. Prepared umbilical artery grafts measuring 1.7+/- 1.0mm in diameter, 10.0 +/- 2.0mm in length, were implanted as interposition grafts into aortas with diameter of 1.5 +/- 1.00mm. Nylon sutures (#10-0) were employed for all diameters. Patency was assessed by ultrasonography, angiography and ultimately at termination of the experiment. Animals were sacrificed at 4, 6 and 12 weeks. Specimens of the grafts and adjacent aorta were submitted for pathologic and genetic evaluations. To determine whether rat cells were ingressing and populating the graft, 1mm samples of the engrafted tissue after 6 and 12 weeks were solubilized in Trizol. Complementary RNA was prepared for hybridization to Affymetrix Rat 2.1 whole transcriptome chips in the Gene Atlas.
RESULTS: Aside from 2 perioperative mortalities in the very beginning of this study, patency was achieved in all animals documented by ultrasonography, angiography or at the time of sacrifice at 4, 6 or 12 weeks. Pathology confirmed retention of the basic architecture of the implanted grafts and no evidence of infiltration of intimal hyperplasia. A stenotic proximal anastomosis in a 6 week specimen was technical in origin. PCR studies showed host cell infiltration of the grafts as early as 6 weeks but particularly at 12 weeks. Preliminary results from the genetic studies suggest remodeling of the human tissue by rat cells based on expression of various adhesion molecule. The costs for the project were significantly lower than if larger animals had been used and most of our studies were performed in rats bred in our laboratory.
CONCLUSIONS: The murine model consisting of aortic interposition with umbilical cord artery grafts is well suited to study the comparative outcomes based on different methods of preparing the graft. Additionally, it is cost-effective and technically feasible in skilled hands.

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