Biomedical Engineering Reference
In-Depth Information
immensely the regenerative outcomes. Indeed, the tissue organization
and architecture of young tissue extracts differs in many ways to those
of older animals [TOT 11]. In addition, if the decellularization process
is too harsh, it can result in the destruction of the ECM structure, the
removal of growth factors and proteoglycans which is in turn
detrimental to the tissue regeneration [LIN 14].
Off the shelf grafts purely rely on the re-colonization of the
implant by the host tissues and therefore can induce large variation in
the regenerative outcome due to a difference in age and health
conditions. Over the last decade, there have been attempts to include
more biological components into the prosthetic used for ligament
reconstruction. This has resulted in the emergence of a field called
ligament tissue engineering, the paradigm of which is the combination
of a biomaterial structure (generally referred to as scaffold), cells and
bioactive molecules. This method is envisioned as the future of
ligament reconstruction and has become a prominent area of research.
The following section describes the main tissue engineering strategies
developed in recent years and elaborates on the challenges that this
field is facing.
7.3. Tissue-engineered constructs
7.3.1.
Cell sheet technology
Although tissue engineering traditionally utilizes porous 3D
structures for delivering the cells
in vivo
, several approaches have
uniquely used cells without any carrier system. This strategy is based
on the capability of the cells to form their own matrix during
in vitro
culture. This results in the formation of a so-called cell sheet, which
can be physically handled without, to some extent, compromising its
integrity. This is generally achieved by culturing the cells (which can
be of various cell types) in 2D with a medium favorable to
collagenous deposition. Hence this approach seems particularly suited
for ligament or tendon tissue engineering as it recapitulates to a large
extent the biological composition of the native tissue (mostly collagen
type I and III). Ascorbic acid is commonly utilized at various
concentrations and in combination with fibroblasts' specific growth
