Evaluation of expanded polytetrafluoroethylene arteriovenous access grafts onto which microvessel-derived cells were transplanted to "improve" graft performance: preliminary results.
The purpose of this study was to implement and evaluate a clinical protocol for following longitudinally the luminal responses of microvessel cell seeded expanded polytetrafluoroethylene (ePTFE) vascular grafts implanted for hemodialysis access. Half of the patients enrolled in the study were randomized to receive grafts that were "seeded" with transplanted microvessel cells derived from autologous subcutaneous fat; the other half of the patients received nonseeded grafts. The patients agreed to scheduled biopsies of their grafts at three postoperative times. All biopsy samples were evaluated by routine histologic and electron microscopy techniques. Three men and six women were enrolled in the study. All operative procedures were tolerated well. However, only two of the nine patients agreed to 1-year postimplantation biopsies; one of these patients had been randomized to receive a "nonseeded" ePTFE graft and one randomized to receive a "seeded" graft. The "seeded" graft at 3 months showed endothelial cells on the luminal surface as well as some intimal thickening. By 20 months, the same "seeded" graft showed significant concentric intimal thickening and by 24 months, this "seeded" graft thrombosed. The "nonseeded" graft at 16 months had irregular areas of intimal thickening which were quite patchy in nature. The flow contacting surface of the "nonseeded" graft remained thin. The intima of the "seeded" graft was twice as thick as that of the "nonseeded" graft. The methodologies implemented in the study design were appropriate. Biopsy samples were obtained without complication and were easily processed for analysis. Patient compliance with the biopsy protocol was problematic however. The study was terminated because of the development of significant concentric intimal hyperplasia in a "seeded" graft.