Interaction of Cells with Decellularized Biological Materials - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 106

1 Introduction
In the search for a method ''designed and constructed to meet the needs of each
individual patient'' [ 1 ], the idea of tissue engineering was created as an interdis-
ciplinary field that applies the principles and methods of engineering and the life
sciences to the development of biological substitutes that restore, maintain, and/or
improve tissue function [ 1 , 2 ]. The concept of ''cardiovascular tissue engineering''
aims to develop viable cardiovascular structures, e.g., heart valves, myocardium,
and blood vessels, which demonstrate mechanisms of remodeling and self-repair,
a high microbiological resistance, complete immunological integrity, and a
functional endothelial cell layer to guarantee physiological hemostasis. Thus,
regardless of the desired tissue type, all tissue engineering approaches rely on four
essential components: (1) tissue-specific cells which form and vitalize the tissue,
(2) signals (chemical and mechanical) which modulate cellular gene expressions
and, thus, extracellular matrix (ECM) production, (3) cellular and humoral
components of the recipient's immune system which allow and facilitate tissue
integration or graft deterioration and destruction, and (4) matrix scaffolds which
maintain these cells in a definite three-dimensional architecture.
2 Native Grafts
As early as the beginning of the eighteenth century, autologous vessel grafts
were used for substitution or reconstructive vascular interventions [ 3 - 5 ].
However, allogeneic vascular grafts were not used until the 1940s. The clinical
application of these prostheses was mainly based on works by Hufnagel [ 6 ] and
Gross at al. [ 7 , 8 ]. Harvested mainly from autopsies, these grafts were sterilized by
cobalt radiation and predominately used for aortic replacement. In the 1950s, the
first tissue banks were established and allogeneic vascular grafts were used to
replace nearly any diseased central or peripheral artery. In the 1960s, Barret-Boyes
[ 9 ] and Ross [ 10 ] were the first to use biological, allogeneic human heart valve
prostheses in the clinical setting. In contrast to mechanical prostheses, the lack of
distracting ''clicking'' noises and oral anticoagulation following the implantation
of these biological valves to avoid thrombembolic complications made these
valves increasingly attractive and the clinical demand by far exceeded their
availability [ 11 , 12 ]. However, degenerative changes were observed 8-10 years
following implantation of both these valvular and vascular grafts, showing up on
X-rays as severe calcifications and indicating ongoing degenerative processes,
which ultimately led to complete graft loss [ 13 - 15 ] and thus required redo
operations.
Another milestone in the history of biological grafts was laid by Rosenberg and
Henderson [ 16 , 17 ], who tried to reduce the immunogenicity of bovine carotid
artery grafts by impregnation with dialdehyde starch. It was anticipated that