Morphological Changes in the Ovine Carotid Artery Wall Induced by Cold Storage

Abstract

Blood vessels obtained from cadavers and amputated limbs stored at 4°C (i.e., cold stored) potentially represent an economical and readily sourced alternative to autologous vessels and synthetic prostheses for vascular reconstructive surgery. However, cold-stored vessels would need to have a reduced antigenicity and an antithrombogenic autologous endothelial cell (EC) lining before they could function as patent vascular allografts. The aim of this study was to determine the effect of cold storage for 1-16 weeks on the morphology of the ovine carotid artery wall. Ovine carotid arteries (n = 6) were rinsed and flushed with 0.9% saline, cut into segments, wrapped in 0.9% saline-soaked gauze, and stored at 4°C for 1, 2, 4, 8, or 16 weeks. Following storage, the segments were sampled and the samples fixed and sectioned for light microscopic, immunohistochemical, or transmission electron microscopic examination. After 1 and 2 weeks the ECs were karyolitic or contained pyknotic nuclei. After 4 weeks the EC layer was depleted, the subendothelial matrix exposed, and the number of smooth muscle cells (SMCs) and fibroblasts reduced. The 8-and 16-week samples demonstrated complete loss of the EC lining and only occasional remnants of SMCs or fibroblasts. The subendothelial basement membrane appeared to undergo degradative changes as early as 1 week following cold storage. At each time point examined, the subendothelial connective tissue stroma, the internal elastic lamina (IEL), and the collagenous and elastic extracellular framework were retained. These results demonstrate that the ovine carotid artery wall progressively loses its cells but retains its extracellular components during cold storage for up to 16 weeks. They suggest that cold-stored vessels may function as allografts with a reduced antigenicity for vascular reconstructive surgery. It is conceivable that seeded autologous ECs may be used to restore the antithrombogenic EC lining prior to graft implantation.