Cardiovascular Tissue Engineering
Kardiovaskuläres Tissue Engineering
Artificial Bypass - Tissue Engineering in Cardiac Surgery
Bypass surgery accounts for more than 50% of the cardiac surgery portfolio in terms of numbers. More than 450,000 bypass operations are performed each year in the USA and Germany alone. Although autologous vascular graft replacement is the gold standard for narrow caliber vascular graft replacement, autologous vascular material is not available in the required amount in many patients due to chronic vascular disease.
Although plastic prostheses are already available as an alternative to autologous vessels, they have not been able to produce long-term results. As an outcome, so-called tissue engineering has increasingly come to the fore in recent decades. Through the artificial production of biological tissues, small-caliber vessels promise high biocompatibility with long-term benefits.
In collaboration with the chemist Prof. Klemm from Jena, it has been possible in recent years to produce artificial vessels from bacterial nanocellulose (BNC) (Fig. 1). The cellulose is thereby formed by Gluconacetobacter xylinus directly as a three-dimensional cylinder - an advantage over current methods in which biotechnologically produced cell mats or similar constructs are secondarily formed into a cylinder. The patented process used in our research group prevents the surface properties from changing as a result of the forming process
By influencing the manipulated variables during the production of the prostheses in the biorector, the targeted and reproducible properties of the resulting vascular prosthesis, such as wall thickness, bursting strength, fiber density or surface quality can be leveraged.
It has already been shown in the large animal model that the material BNC has good biocompatibility and due to the material properties, has excellent surgical use (Fig. 2) .1,2 For this purpose, a large animal model was created, in which the common carotid artery of sheep was replaced by an interponate. An initial epithelialization with migration of the body's own cells in the sense of a conversion to a three-layered vessel wall structure was shown (Fig. 3).
In the long-term follow-up (> 12 months), patency rates of up to 70% have been achieved so far. Openness rates> of 90% are essential before potential human use. Therefore, the research focus is currently in the evaluation and improvement of various novel BNC variants. For this purpose, a so-called Chandler-Loop model was established (Fig. 4). In this in-vitro procedure, the interactions between the cellular and acellular components of the blood and the BNC surface can be investigated. By means of various coatings with e.g. Endothelioids molecules, the ingrowth of the vascular prosthesis is to be further improved. In order to achieve better results in future in-vivo experiments, epithelialization should be characterized and improved in an in-vitro flow simulator.
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