Search

Purpose: The purpose of this study was to explore new strategies for enhancing specific cell type attachment to biomaterials using immobilized lectins for cell surface glycoconjugates. The lectin Ulex europaeus I (UEA I) has a high affinity for human vascular endothelial cell surface glycoconjugates. Methods: UEA I was covalently bound to polyethylene terephthalate (Dacron) with the cross-linking agent 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride to achieve oligosaccharide-mediated endothelial cell attachment to this otherwise nonadherent surface. Results: Experiments with radiolabeled UEA I demonstrated covalent linkage of as much as 1.35 μg/cm 2 . The lectin binding site is available after the reaction, as demonstrated in experiments a neoglycoprotein. Adhesion studies reveal a 100-fold increase in endothelial cell attachment for the UEA I/polyethylene terephthalate surface (99.7 ± 29.6 cells/high-power field) when compared with untreated (0.7 ± 0.5), crosslinking agent (0.4 ± 0.3), and denatured UEA I (1.2 ± 1.1) control groups. Five vascular endothelial cell lines adhered to the UEA I/polyethylene terephthalate surface, whereas monocytes, smooth muscle cells, and fibroblasts did not. Conclusion: These results imply new strategies for endothelialization of prosthetic grafts and promotion of selective cell adherence to biomaterials, with emphasis on carbohydrate interactions. Moreover, this experimental system offers a model for exploring the biologic significance of the endothelial cell-UEA I ligand. (J VASC SURG 1993;18:486-94.)

Remission plasma samples of some patients with chronic relapsing thrombotic thrombocytopenic purpura (TTP) contain unusually large von Willebrand factor (vWF) multimers similar to those produced by normal human endothelial cells in culture. The infusion of the cryosupernatant fraction of normal plasma is as effective as normal fresh-frozen plasma (FFP) in the treatment or prevention of TTP episodes in patients with the chronic relapsing form of TTP. Three patients with chronic relapsing TTP during remission have unusually large vWF multimers present in their plasma. Two of the patients were transfused once with FFP, one of the two received cryosupernatant on three occasions, and the third patient was studied before and immediately after plasma exchange. Unusually large vWF multimers decreased or disappeared from patient plasma samples within 1/2 to 1 1/2 hours following the transfusion of FFP (on two occasions) or cryosupernatant (on two of three occasions), and immediately after plasma exchange (on one occasion). The patient who received cryosupernatant was studied serially after the infusions. Unusually large vWF multimers returned to her plasma within ten to 24 hours and persisted thereafter. Unusually large vWF multimers did not disappear from patient remission plasma samples, or from the culture medium removed from normal human endothelial cells, when these fluids were incubated in vitro with either normal FFP or cryosupernatant. We conclude that an activity in FFP, and its cryosupernatant fraction, promoted the rapid in vivo disappearance of unusually large vWF multimers from the plasma of two patients with chronic relapsing TTP in remission, and plasma exchange reversed the abnormality in a third patient who was in partial remission. Neither FFP nor cryosupernatant directly converted unusually large multimers to smaller vWF forms in vitro in the fluid phase. These results indicate that an activity in the cryosupernatant fraction of normal plasma is involved in vivo in controlling the metabolism of unusually large vWF multimers, and that this process is defective in some chronic relapsing TTP patients.

Graft thrombosis soon after reconstruction remains a major obstacle to the use of reversed vein grafts in infrapopliteal reconstruction. Our clinical experience with in situ vein grafts corroborates Leather's results by demonstrating an overall graft patency of 95% below the knee at 1 year and 94% in the infrapopliteal group. It has been postulated that this improved early patency rate of in situ vein grafts is the result of more optimal preservation of the endothelium of the vein graft. To investigate this hypothesis, human saphenous veins were handled by an in situ and a reversed technique. The intact vein segments were then tested for luminal production of prostacyclin and thromboxane A 2 and fixed for scanning electron microscopic analysis of the surface morphology. This study demonstrated that endothelial cell prostacyclin release is enhanced in human in situ vein segments but not in reversed vein segments. In addition, luminal production of thromboxane A 2 is significantly greater in the reversed than in the in situ vein segments. These findings are associated with marked endothelial structural damage in the reversed veins and minimal endothelial disruption in the situ veins. Therefore the ratio of the antiaggregatory vasodilator prostacyclin to the proaggregatory vasoconstrictor thromboxane A 2 is significantly more favorable for the in situ vein segment than for the reversed vein segment. The observed excellent early patency of the situ vein grafts in our poor-risk patient population may in part be the result of this favorable balance of prostacyclin and thromboxane A 2 and the more optimally preserved endothelial morphology. (J VASC SURG 1984;1:149-59.)

Plasma VIII:von Willebrand factor antigen (VIII:vWF) levels were elevated approximately two- to eightfold in seven patients (three adults and four children) during acute episodes of thrombocytopenia, renal failure, and hemolytic anemia (the hemolytic-uremic syndrome, HUS). In all seven patients, there was an alteration in plasma VIII:vWF patterns during these acute HUS episodes, so that the largest VIII:vWF forms were relatively decreased. Plasma VIII:vWF multimer patterns returned to normal, or nearly to normal, as platelet counts returned to preexisting levels, even in the patients whose recovery of renal function was incomplete and whose plasma VIII:vWF antigen level remained above normal. The sister of one of the HUS patients had a similar clinical prodrome (gastroenteritis) that was not followed by thrombocytopenia or renal failure and was not accompanied by an elevated level or abnormal forms of plasma VIII:vWF. These results suggest that an alteration in VIII:vWF metabolism, distribution, or interaction with platelets is associated with acute HUS episodes. In contrast to patients with chronic relapsing thrombotic thrombocytopenic purpura, none of the HUS patients (either during or after the acute HUS episodes) had a defect in the conversion of unusually large VIII:vWF multimers derived from endothelial cells to the VIII:vWF forms found in normal plasma.

As a 51-year-old woman recovered from an initial acute episode of thrombotic thrombocytopenic purpura (TTP), her plasma was found to contain unusually large von Willebrand factor (vWF) multimers. Clinical, hematological, and vWF studies of her siblings and children were normal. The unusually large vWF forms were presumably derived from endothelial cells, persisted in her plasma after recovery, and were associated with recurrent episodes of TTP during the subsequent 6 months. After the last episode of relapse they disappeared from her plasma following 3 1/2 weeks of therapy with prednisone and did not return during 17 months of treatment with prednisone and/or azathioprine. She is now receiving no drugs, has normal plasma vWF forms, and has not had any more episodes of TTP. We conclude that our patient had an acquired defect in the conversion of unusually large vWF multimers derived from endothelial cells to the somewhat smaller vWF forms usually present in circulation. The defect may have been immune-mediated, because it was eliminated during therapy with immunosuppressive drugs.