Angiogenese-Gentherapie mit AdVEGF₁₆₅ - Eine Art „Delay“ für Lappenplastiken?

Zusammenfassung

Eine normale Gewebefunktion ist auf die adäquate Sauerstoff- und Nährstoffversorgung durch Blutgefäße angewiesen. Die Abläufe der Bildung und Reifung von Gefäßen werden initiiert und aufrechterhalten durch unterschiedliche Wachstumsfaktoren. Dem Wachstumsfaktor VEGF kommt in diesen Prozessen eine herausragende Bedeutung zu. Die Erzeugung subletaler Ischämie als Angiogenesereiz ist unter dem Namen „Delay“ ein in der Plastischen Chirurgie etabliertes Verfahren, deren zugrunde liegende molekularbiologische Mechanismen jedoch weitgehend unbekannt sind. Ziel der vorliegenden Arbeit ist die weitere Aufklärung des Zusammenhangs zwischen VEGF und dem Delay-Phänomen, insbesondere im Vergleich zur adenoviralen Gentherapie als potenziell konkurrierendes, nicht-invasives Verfahren. An 32 männlichen Crl:CD(SD)-Ratten wurde die VEGF-Konzentration in Haut und Muskulatur nach subdermaler Injektion von AdCMV.VEGF₁₆₅ oder reiner Umschneidung (Delay) einer überdimensionierten Lappenplastik vom „Random-pattern“-Typ gemessen und mit Kontrollen verglichen. Weiterhin wurden nach VEGF-Gentherapie oder Delay nach jeweils sieben Tagen die Lappenplastik gehoben und die Auswirkung der Therapie auf die postoperative Durchblutung mittels Indocyaningrün-Laser-Fluoreszenzangiographie und auf die Größe der überlebenden und nekrotischen Lappenfläche untersucht. Im Hautanteil der Lappenplastiken in der VEGF-Gentherapie-Gruppe und der Delay-Gruppe konnten jeweils gegenüber den Kontrollen signifikant erhöhte VEGF-Konzentrationen nachgewiesen werden. In der angrenzenden Muskulatur zeigten sich keine signifikanten Unterschiede zwischen den Gruppen. Bei der Messung der Perfusion unmittelbar postoperativ wies nur die VEGF-Gentherapie-Gruppe einen signifikant erhöhten Perfusionsindex gegenüber den Kontrollen auf. Die Messung der überlebten Lappenfläche ergab für die AdVEGF-Gruppe eine signifikante Erhöhung gegenüber der Kontroll- und der Delay-Gruppe. Das Delay-Verfahren resultiert in einer signifikant und lokalisiert erhöhten Konzentration des Wachstumsfaktors VEGF. Die gentherapeutische Verwendung dieses Wachstumsfaktors alleine ist in der Lage, die Hautdurchblutung zu steigern und die Entstehung von Nekrose zu reduzieren. Bei Gentherapie mit VEGF und Delay scheinen ähnliche Phänomene abzulaufen, wobei die Therapie mit AdVEGF eine deutliche Überlegenheit zeigt.

Abstract

A regular tissue functioning requires the adequate supply of oxygen and nutrient via blood vessels. The sequences of formation and maturation of vessels are initiated and maintained by different growth factors. The VEGF growth factor plays an exceptional role in these mechanisms. The creation of sublethal ischemia as an angiogenic stimulus known as “Delay” is a well established procedure in plastic surgery, although the underlying molecular biological mechanisms still remain unknown. The important role of VEGF and its regulation depending on oxygen pressure suggest a strong connection between this growth factor and the delay phenomenon. The VEGF concentration in skin and underlying muscle was measured in overdimensioned random pattern flaps on 32 male Sprague-Dawley rats after either VEGF gene therapy or circumcision without elevation of the flap and compared to controls. Additional random pattern flaps were raised seven days post gene therapy or delay. The effect on the flap perfusion was measured postoperatively using Indocyanine green Laser Fluoroscopy and the size of the surviving and necrotic areas of the flaps were analysed. The skin of the random pattern flaps showed both in the Delay group and in the VEGF gene therapy group a significantly elevated VEGF concentration compared to the controls. The underlying rectus abdominis muscle showed no significant differences in VEGF concentration between the groups. The flap perfusion postoperatively was significantly increased solely in the VEGF gene therapy group. The analysis of the surviving area of the flaps showed a significant increase over the controls in the gene therapy group. The Delay procedure results in a significantly and locally raised concentration of the VEGF growth factor. The gene therapeutical use of this growth factor allows us to raise flap perfusion and to reduce necrosis. Both VEGF gene therapy and Delay seem to promote similar mechanisms whereas the gene therapy produced superior results in this setting.

Schlüsselwörter

VEGF - Gentherapie - Delay-Technik - Komplikation Lappenplastik - Random-pattern-Typ

Key words

VEGF - gene therapy - delay technique - flap necrosis - random pattern flap

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