The placement of arteriovenous loops can enable microvascular anastomoses of free flaps when recipient vessels are scarce. In animal models, elevated fluid shear stress in arteriovenous loops promotes neoangiogenesis. Anecdotal reports in patients indicate that vein grafts used in free flap reconstructions of ischemic lower extremities are able to induce capillary formation. However, flow-stimulated angiogenesis has never been systematically investigated in humans, and it is unclear whether shear stress alters proangiogenic signaling pathways within the vascular wall of human arteriovenous loops.
Eight patients with lower extremity soft-tissue defects underwent two-stage reconstruction with arteriovenous loop placement, and free flap anastomoses to the loops 10 to 14 days later. Micro-RNA (miRNA) and gene expression profiles were determined in tissue samples harvested from vein grafts of arteriovenous loops by microarray analysis and quantitative real-time polymerase chain reaction. Samples from untreated veins served as controls.
A strong deregulation of miRNA and gene expression was detected in arteriovenous loops, showing an overexpression of angiopoietic cytokines, oxygenation-associated genes, vascular growth factors, and connexin-43. The authors discovered inverse correlations along with validated and bioinformatically predicted interactions between angiogenesis-regulating genes and miRNAs in arteriovenous loops.
The authors’ findings demonstrate that elevated shear stress triggers proangiogenic signaling pathways in human venous tissue, indicating that arteriovenous loops may have the ability to induce neoangiogenesis in humans. The authors’ data corroborate the nutrient flap hypothesis and provide a molecular background for arteriovenous loop–based tissue engineering with potential clinical applications for soft-tissue defect reconstruction.
Ludwigshafen, Homburg-Saar, and Saarbruecken, Germany
From the Department of Hand, Plastic, and Reconstructive Surgery, University of Heidelberg, BG Trauma Center Ludwigshafen; the Institute of Human Genetics and the Institute of Clinical Bioinformatics, Saarland University; and the Department of Vascular Surgery, Ludwigshafen Hospital.
Received for publication October 4, 2017; accepted March 5, 2018.
The last two authors contributed equally to this work.
Disclosure: The authors have no financial disclosures. The funding of this study was solely institutional.
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Dominic Henn, M.D., Department of Hand, Plastic and Reconstructive Surgery, BG Trauma Center Ludwigshafen, Department of Plastic Surgery, University of Heidelberg, Ludwig-Guttmann-Straße 13, 67071 Ludwigshafen, Germany, email@example.com