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Scanning electron microscopic changes in morphology of pulmonary endothelium in rat lung isografts following hypothermic ischaemic storage and transplantation.

Endothelial monolayer integrity is a critical factor limiting vascular permeability of solid organs in transplantation. Several in vitro, ex vivo and in vivo studies suggest that damage to endothelial cells (EC) due to hypothermia and ischaemia-reperfusion injury causes morphological and functional damage to the endothelium leading to parenchymal oedema and haemorrhage. Aiming to study morphological changes to arterial pulmonary EC subjected to transplantation procedures, random scanning electron micrographs of vascular endothelium of rat lungs were taken. Forty-eight rat lungs were hypothermically stored for 48 or 72 hours in two different preservation solutions and studied either at the end of the cold storage period, or 5 min, 24 h or 4 weeks following transplantation. After 5 minutes of revascularization, micrographs showed EC shape variations, bleb formation and cell retraction with intercellular gap formation. Twenty-four hours after transplantation loss of monolayer continuity was widely extended. Four weeks of revascularization resulted in either well preserved specimens with nearly normal endothelium, or badly preserved arteries with fibrotic degeneration of the luminal vessel wall. The morphological disruptions found in this study help to explain the alterations in permeability control and vascular dysfunction observed in lung transplantation.