ENDOTHELIALIZATION OF POLYESTER VASCULAR PROSTHESES IN CANINE: THE SIGNIFICANT ROLE OF TRANSMURAL COMMUNICATION AT A SUB-CELLULAR LEVEL 

Ze Zhang, Yvan Douville, Nathalie Gilbert
Department of Surgery, Faculty of Medicine, Laval University; the Research Center of Saint-François d’Assise Hospital,  Quebec City, Quebec, Canada

Stephen Briana, Hugh Zhao
Thoratec Corporation, Pleasanton, CA, USA
 

 The importance of microporous and water permeable wall for the healing of polyester (Dacron) vascular prostheses has been known for a long time. However, the significance of its permeability to soluble substances at sub-cellular level has not been demonstrated. Polyester arterial prostheses were prepared in such a way that each of them contained three segments, of which at least one segment was impervious and another segment was permeable to water but impermeable to cells. Twenty graft segments were implanted in 7 dogs as a thoraco-abdominal bypass for two months. The prostheses were then harvested, longitudinally opened and photographed before fixation. The explants were fixed in formalin and treated for histological staining with hematoxylin-eosin, Weigert, and Masson’s trichrome for the identification of cells, elastin fibres, and collagenous tissues, respectively. Immunohistological staining was performed to identify endothelial cells, smooth muscle cells and fibroblasts. Scanning electron microscopy was carried out to investigate the morphology of the lumen of the grafts. The low porosity graft capped by two thrombogenic segments was fully endothelialized, proving that the endothelial cell lining in the middle segment was originated from circulating cells (fallout mechanism). The striking contrast with its impermeable counterpart demonstrated that a wall permeable to small substances of sub-cellular level may be critical for the endothelial healing. A wide range of water permeabilities did not reveal advantages of high water permeable segments over low water permeable ones. Endothelial ingrowth from anastomoses was also jeopardized in the absence of wall permeability. In conclusion, transmural communication at a sub-cellular level may have played a critical role in the fallout based-endothelialization of arterial prostheses in canine. This highlights the potential function of perigraft cytokines and growth factors in endothelial healing.