Time‐related Histopathologic Changes in Fresh Frozen Carotid Xenografts in a Pig‐to‐Goat Implantation Model

Abstract

We performed an animal experiment with an emphasis on time-related histopathologic changes to evaluate the clinical feasibility of immunologically nontreated xenogenic vascular grafts. Bilateral porcine carotid arteries were harvested, and then, after short-term freezing at -70 degrees C, interposed into goats' carotid arteries. An antiplatelet agent was administered orally for 3 months postoperatively. The goats were randomly assigned to five periods of observation (1 week, and 1, 3, 6, and 12 months after implantation); two animals were observed at each of these times. Doppler ultrasonography was performed periodically during the observation period. At predetermined times, grafts were explanted and examined using hematoxylin and eosin, and Masson's trichrome stains. Immunohistochemical evaluations were conducted with T-lymphocyte indicator and von Willebrand factor. Two goats died prematurely, one from respiratory problems related to anesthesia and the other from pneumonia. A total of 16 grafts from the remaining eight animals were evaluated. Grafts were all patent except one at 3 months after transplantation. Histologically, xenogenic arterial grafts showed early endothelial cell loss at 1 week. This was followed by a progressive spread of recipient endothelial cells from the anastomotic site, and re-endothelialization was complete at 1 month. The degree of neointimal and medial thickening increased until 3 months, and then decreased. At 12 months, no additional growth of the intimal or medial layers was observed. Adventitial inflammation became severe at 3 months, but was reduced at 6-12 months. The proportions of CD3-positive T-lymphocytes among inflammatory cell infiltrations were very low. Fresh frozen xenogenic arterial grafts showed acceptable patency throughout the 12-month period and showed no evidence of being unduly influenced by rejection reactions.

A short-term decellularisation technique for porcine carotid arteries that conveys a structural stimulus to cells

“…however, this study as well as the others suggest that the initial act of preserving cell viability could be key to preventing ECM damage [38,39]. Like decellularisation, variations in cryopreservation methods are plentiful and can depend on specific characteristics of the tissue being preserved.…”

“…The technique of cryopreservation was originally developed for the long-term storage of isolated cells, and cryopreservation of tissues poses challenges to internal structure, compartmental organisation and cell types [37]. Given the later application of decellularisation, the preserved cell viability aspect of cryopreservation is redundant; however, this study as well as the others suggest that the initial act of preserving cell viability could be key to preventing ECM damage [38, 39]. Like decellularisation, variations in cryopreservation methods are plentiful and can depend on specific characteristics of the tissue being preserved.…”

“…Cryoprotectant agents are commonly used in conjunction with nourishing vehicle solutions to both support the native cell population and prevent ECM disruption [44]. Other studies have previously reported that unprotected freezing of arteries cause vascular SMCs to show various signs of cell stress, and the absence of a cryoprotectant is known to induce ice crystal formation which in turn disrupts cell membrane integrity and damages surrounding tissue [25, 38]. This study utilised a previously published cryopreservation method specifically for human vessels and confirmed that cryopreservation does not impact vascular structure (Figure 1-Figure 3) [45].…”

Artificial Organs 2009: A Year in Review

“…Ji M. Chang and Won G. Kim (136) of the Seoul National University College of Medicine, Seoul, Korea evaluated the time‐related histopathologic changes of immunologically nontreated xenogenic vascular grafts. Bilateral porcine carotid arteries were harvested, frozen at −70°C, and interposed into goats' carotid arteries.…”