Ann Thorac Surg 2005;79:1465-1466
© 2005 The Society of Thoracic Surgeons
Correspondence
Endothelialization and Functional Neointima on Vascular Grafts in Humans: Reply
Thorsten Walles, MD,
Heike Mertsching, PhD
Department of Thoracic and Vascular Surgery Heidehaus Hospital Am Leineufer 70 Hannover, 30419 Germany
(E-mail: twalles{at}yahoo.com).
To the Editor:
We thank Dr Tomizawa for his interest in our publication and for his critical remarks. It appears that the interpretation of our findings leads us into the arena of advocates for synthetic scaffolds and proponents for the use of biological matrices for vascular tissue engineering [1].
Synthetic materials are excessively thrombotic when used to bypass arteries <6 mm in diameter, with thrombosis rates higher than 40% after 6 months [2]. The first successful isolation of endothelial cells from venous segments and their subsequent transplantation onto synthetic vascular grafts was hoped to improve graft properties. The literature review of Dr Tomizawa mirrors the application of numerous synthetic materials and fabrics to accommodate endothelial cells hoping to create a functional endothelial lining overcoming the problem of early vascular graft thrombosis. However, despite ample efforts, currently no clinically applicable artificial functional small diameter vascular graft is available [3]. In contrast, tissue engineered vascular 4-mm diameter constructs composed entirely of natural materials responded to contractile agonists and showed excellent patency rates up to 3 months after implantation [4].
In our study [5], we showed that the luminal recellularization of synthetic vascular prostheses did not represent functional endothelium but rather fibrous tissue. Our conclusions, based to a greater extent on the functional protein biochemical findings in the isolated cells recovered from the tested neointima and to a lesser extent on macroscopical and immunhistochemical results, are in accordance with recent discoveries in the field [4] favoring biological matrices for vascular tissue engineering. Recent perceptions point toward the relevant interplay of endothelial cells, smooth muscle cells and fibroblasts, and diversified extracellular matrix components in forming a functional intimal lining [6]. Our knowledge about this interplay is fragmentary and can be mimicked experimentally only by the use of biological matrices until we do not understand the role of each component in this orchestra.
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References
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- Fuchs JR, Nasseri BA, Vacanti JP. Tissue engineering: a 21st century solution to surgical reconstruction Ann Thorac Surg 2001;72:577-591.[Abstract/Free Full Text]
- Niklason LE, Gao J, Abbott WM, et al. Functional arteries grown in vitro Science 1999;284:489-493.[Abstract/Free Full Text]
- Nerem RM, Seliktar D. Vascular tissue engineering Annu Rev Biomed Eng 2001;3:225-243.[Medline]
- Huynh T, Abraham G, Murray J, Brockbank K, Hagen PO, Sullivan S. Remodeling of an acellular collagen graft into a physiologically responsive neovessel Nat Biotechnol 1999;17:1083-1086.[Medline]
- Walles T, Görler H, Puschmann C, Mertsching H. Functional neointima characterization of vascular prostheses in human Ann Thorac Surg 2004;77:864-868.[Abstract/Free Full Text]
- Matsuda T. Recent progress of vascular graft engineering in Japan Art Org 2004;28:64-71.
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