Development of implantable autologous small-calibre vascular grafts from peripheral blood samples.

INTRODUCTION: At present the generation of a small-calibre (≤5 mm) vascular replacement for artificial bypasses remains a challenge for tissue engineering. The biocompatibility of bioartificial vessel replacements is of decisive significance for function and depends on the materials used. A completely autologous vessel substitute must exhibit high biocompatibility and functionality. For this purpose we developed and optimised a technique for the engineering of an autologous bypass material from a fibrin scaffold and vascular cells isolated from the same sample of peripheral blood in a porcine model. MATERIALS AND METHODS: Fibrinogen, late outgrowth endothelial and smooth muscle cells were isolated from peripheral blood samples (n=14, 100 mL each). Fibroblasts were isolated from porcine aortic adventitial tissue (n=4). Tubular seeded fibrin segments were obtained using an injection moulding technique with the simultaneous incorporation of the in vitro expanded cells into the fibrin matrix. The segments were cultivated under dynamic conditions with pulsatile perfusion in a bioreactor. Morphological and functional characterization was done. RESULTS: Artificial vascular segments with a length of 150 mm were reproducibly obtained with a hierarchical arrangement of incorporated cells similar to the structure of the vascular wall. By additional seeding of fibroblasts, suturable segments with biomechanical properties suitable for implantation into the arterial system were obtained. CONCLUSIONS: Implantable bioartificial vascular grafts can be generated from blood. After cultivation under dynamic conditions the vascular segments possess a structure similar to that of the vascular wall and exhibit biomechanical properties sufficient for implantation as arterial substitutes.

New developments in tissue engineering of vascular prosthetic grafts.

Despite remarkable developments in vascular medicine in the last decades and intensive research on the improvement of bypass materials, an ideal bypass graft comparable to autologous veins or arteries is still not available for peripheral vascular and coronary artery bypass grafting. This article reviews established bypass materials and provides an overview over interesting new technologies particularly those associated with tissue-engineering and those already adopted clinically.

Diagnostic and surgical treatment of the thrombophlebitis in the saphenofemoral junction.

PURPOSE: This retrospective study reports on the diagnostic and surgical treatment of 10 patients with ascending thrombophlebitis in the proximal great saphenous vein with free-floating thrombi reaching into the common femoral vein. MATERIALS AND METHODS: 10 patients were operated in our clinic for thrombophlebitis with free-floating thrombi in the saphenofemoral junction. Diagnosis of free-floating thrombi was made by B-mode and color-coded duplex ultrasound examination. Surgical thrombectomy was performed immediately. RESULTS: No operative complications were observed, while 5 of 10 patients sustained preoperative pulmonary embolism. After successful thrombectomy and perioperative systemic heparinization, patients who had no PE and no thrombophilic disorders were discharged without any further anticoagulant therapy. CONCLUSION: The results of our retrospective study show that patients with an ascending thrombophlebitis should undergo ultrasound examination to detect free-floating thrombi reaching into the deep venous system. In case of free-floating thrombi, immediate surgical thrombectomy, which is safe and provides rapid recovery from symptoms, is indicated.

Autologous blood vessels engineered from peripheral blood sample.

OBJECTIVE: Although many efforts have been made to generate small-diameter (< or =5mm) vascular grafts by means of tissue engineering, improvement in patency and functionality still remains a great challenge. It is our hypothesis that to achieve long-term functionality and patency, not only the complete lining with endothelial cells but also full biocompatibility is essential. DESIGN: The aim was the development of a conduit from a scaffold and endothelial progenitor cells (EPC) separated from peripheral blood of a single donor. MATERIALS AND METHODS: EPC and a fibrin preparation were separated from porcine peripheral blood. Fibrin segments were generated seeded with EPC and were perfused in a bioreactor in vitro. RESULTS: From 100ml blood 12-15 cm long fibrin tubes were successfully generated lined with endothelial-like cells. Seeded tubes showed a remarkable elasticity and burst strength up to 90 mm mercury. CONCLUSIONS: Stable fibrin tubes were successfully generated completely lined with an endothelium-like monolayer from fibrin and EPC, both isolated from the same volume of blood. Although their stability is not those needed for arterial grafting, our results raise the hope, that with distinct improvements in future studies functional autologous vascular grafts could be engineered from the patient's own blood.

[Phytobezoars: case report and review of the literature]. / Phytobezoare: Kasuistik und Literaturübersicht.

We report on the case of a 40-year-old woman with a long year history of vegetarian lifestyle, who experienced a phytobezoar induced acute abdomen due to a mechanic small bowel ileus. After uncomplicated surgical treatment and post-OP course the patient could be discharged on post-OP day 10. Beside a description of the historical background, relevant diagnostic and therapeutic aspects are mentioned as well as a review of the relevant literature.

Use of a fibrin preparation in the engineering of a vascular graft model.

OBJECTIVE: Morphological and functional characterization of cocultured endothelial cells (EC) and myofibroblasts (MFB) seeded on a matrix composed of a fibrin preparation mimicking the microenvironment of a vascular wall. METHODS: MFB and EC were isolated from human saphenous veins and expanded separately in vitro. MFB were seeded on a composite matrix consisting of a fibrin preparation (with or without transforming growth factor-beta2) and a polyglactin-mesh to form a 3-dimensional structure, which was consecutively reseeded with EC. Seeded matrices were incubated in a bioreactor. Characterization was done including fluorescence staining, live-/dead-assay and immunohistochemistry. RESULTS: High density cocultures in hierarchical structure mimicking the formation of a vascular wall were obtained with nearly complete coverage of the surface with EC. Distribution of preseeded MFB in a 519+/-27 microm thick layer (day 14) was achieved. Cell viability was shown in fluorescence staining for at least 19 days. In deeper layers, no viable cells could be detected within the fibrin preparation. EC covered the surface, had uniform morphology, and their preserved viability was shown for at least 5 days. No EC-ingrowth was found into the fibrin preparation. Neoformation of the matrix proteins laminin and collagen IV was observed. CONCLUSION: A structured coculture of MFB and EC was obtained mimicking the formation of a vascular wall with preserved viability utilizing a fibrin preparation. Nutrition problems seem to limit the maximal extent of MFB in the matrix.

Tissue-engineered bioprosthetic venous valve: a long-term study in sheep.

OBJECTIVE: to develop a graft bearing an immunologically tolerated tissue-engineered venous valve (TE graft) that will be incorporated into a native vessel, and restore normal valve function for the treatment of chronic venous insufficiency. METHODS: twenty-four TE grafts were grown using decellularised allogeneic ovine veins as donor matrix, which was subsequently repopulated with the future recipient's myofibroblasts (MFB) and endothelial cells (EC). TE grafts were implanted into the external jugular vein. Animals were sacrificed at 1, 6, and 12 weeks (n=4, each). Autografts served as controls (1 week, n=4; 6 weeks, n=4). Specimen for histology and immunohistochemistry were taken. RESULTS: the matrix was successfully repopulated with MFB and EC (n=8). Patency on venography in the TE graft-group was44,44, and 34 at 1, 6, and 12 weeks, and44 (44) in autografts at 1 (6) weeks, respectively. Except for 2 TE grafts after 12 weeks, valves were competent (duplex ultrasound). Patent TE grafts were merely distinguishable from autografts with minor inflammatory reactions. Reflux was caused by neo-intima formation related to the basis of the TE graft. CONCLUSION: acellularisation and consecutive in vitro autogeneic re-seeding of valved venous conduits can lead to immunologically acceptable, patent, and competent implants in sheep.