Progression of changes in arteries following cold storage preservation in UW and collins solution in a syngeneic aortic transplant model

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Progression of Changes in Arteries Following Cold Storage Preservation in UW and Collins Solution in a Syngeneic Aortic Transplant Model D.A.H. Neil, S.H. Maguire,

M. Walsh, S.V. Lynch, I.R. Hardie, and D.J. Effeney

T

HE pathogenesis of accelerated graft arteriosclerosis is uncertain and probably multifactorial. There is increasing evidence suggesting cold ischemia time (preservation time) to be a critical factor.lm6 This study documented the arterial injury associated with cold storage preservation and followed these changes after syngeneic transplantation to determine if preservationreperfusion injury (PRI) caused long-term injury to transplanted vessels. METHOD The infra-renal aortae of 18 Wistar rats were harvested using a minimal touch technique. Six were stored in UW and 6 in Collins (C) solution at 4°C for 24 hours and then processed for electron microscopy; 6 control arteries were fixed immediately after harvesting. One hundred sixty-eight syngeneic orthotopic infrarenal aortic transplants were performed, 84 were flushed with either UW or C; 42 of each were transplanted immediately and 42 stored for 24 hours at 4°C prior to transplantation (24UW, 24C). Grafts were harvested after 1 day, 1 week, and 1, 3, 6, and 12 months; half of each graft was examined by light and half by electron microscopy. RESULTS

The endothelium remained intact after harvesting of the aortic segment and following cold storage. Cold storage in UW solution produced no ultrastructural evidence of endothelial cell injury and minimal ultrastructural evidence of injury to the media consisting of peripheral clumping of nuclear chromatin and mild cytoplasmic swelling. Storage in C solution resulted in gross cytoplasmic and mitochondrial swelling of endothelial cells with peripheral clumping of the nuclear chromatin. This injury was severe, but could not be classified as irreversible on ultrastructural criteria. The medial smooth muscle cells showed moderate swelling of the mitochondria, peripheral clumping of the nuclear chromatin, and swelling of the cytoplasm, a reversible injury. Grafts harvested 1 hour after transplantation showed a reperfusion injury, consisting of partial endothelial desquamation, leukocyte adherence to, and infiltration of the endothelium. Platelets adhered to both areas of endothelial loss and to the remaining endothelium. The medial injury consisted of smooth muscle cell swelling and the formation of large intra- and extra-cytoplasmic vacuoles. The injury 0 1997 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 Transplantation

Proceedings,

29, 2561-2562

(1997)

was similar in both 24UW and 24C grafts with the exception that the endothelial swelling persisted in the 24C grafts. Re-endothelialisation occurred by 1 day in the 24UW grafts and 1 week in the 24C grafts. Leukocyte numbers in the intima returned to control values at 1 week. The medial vacuoles were no longer apparent one day after transplantation. Neointimal hyperplasia did not develop in any of the groups out to 1 year; however there was an increase in intimal proteoglycan in all groups with time. The 24C grafts developed pools of proteoglycan in areas devoid of smooth muscle cells at 1 week. Similar areas were apparent in the 24UW grafts at 1 month. These persisted to 1 year. There were no associated changes in the elastic laminae and control groups did not develop similar areas.

DISCUSSION

This study shows that a nonimmunological PRI can result in long-term structural changes in arterial walls. Proteoglycan accumulates in the media of arteries of human cardiac allografts which have graft arteriosclerosis,7 a feature of this model. Neointimal hyperplasia develops in another syngeneic aortic transplant model of cold ischemia.a These studies, together with accumulating clinical data,lm6 suggest an etiologic role of PRI to the intima and media of arteries in the development of accelerated graft arteriosclerosis. PRI occurs in transplanted vessels and results in long-term structural alterations in the vessel wall in both well and poorly preserved grafts. This may be a factor in the development of accelerated graft arteriosclerosis.

From the Department of Surgery, University of Queensland, Brisbane, Australia. This work was funded by grants from the NH&M!%, PAH R&D Foundation, & RACS. Dr D. Neil was funded by the Charles M. Lilley, the Richard and Elizabeth Court Scholarships and an NH&MRC Medical Postgraduate Scholarship. Address reprint requests to Dr Desley Neil, Liver Research Laboratories, Clinical Research Block, Queen Elizabeth Hospital, Edgbaston, Birmingham, UK B15 2TH.

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