Biomedical Engineering Reference
In-Depth Information
An ideal cell removal method would not compromise graft structure and mechanical
properties.
Cartmell JS & Dunn MG (Cartmell JS & Dunn MG 2000) compared the effects of three
extraction chemicals [t-octyl-phenoxypolyethoxyethanol (Triton X-100), tri(n-
butyl)phosphate (TnBP), and sodium dodecyl sulfate (SDS)] on tendon cellularity, structure,
nativity, and mechanical properties.
Treatment with 1% SDS for 24 h or 1% TnBP for 48 h resulted in an acellular tendon matrix
with retention of near normal structure and mechanical properties, cell removal using SDS
and TnBP, suggested these treatments are potentially useful for removing cells from tendon
allografts or xenografts without compromising the graft structure or mechanical properties.
In order to function as a living tissue, it is essential that the acellular scaffold is
recellularized either in vivo or in vitro prior to implantation, so that remodeling of the
scaffold to maintain the correct ultrastructural and physical properties can occur.
Recellularization in vitro allows for further conditioning of the graft prior to implantation,
and hopefully a more successful outcome.
Several approaches have been developed to reseed scaffolds that are used in tissue
engineering, including static culture, pulsatile perfusion and centrifugal force. However, the
recellularization in most cases was not homogenous or required large numbers of cells.
Harrison RD Gratzer PF (Harrison RD & Gratzer PF 2005) developed a decellularized bone-
anterior cruciate ligament, demonstrating that Triton-X-and TnBP-treated ligaments were
more receptive to cellular ingrowth than SDS-treated samples.
Woods T & Gratzer PF (Woods T & Gratzer PF 2005) reported that TnBP treatment slightly
decreased the collagen content of the anterior cruciate ligament, but did not alter its
mechanical properties.
In a study, Ingram JH et al. (Ingram JH et al. 2007) have decellularized a porcine patella
tendon scaffold with hypotonic buffer, 0.1% (w/v) sodium dodecyl sulfate (SDS), then used
an ultrasonication treatment in order to produce a microscopically more open porous
matrix; cells seeded onto the fascicular scaffolds penetrated throughout the scaffold and
remained viable after 3 weeks of culture.
Deeken CR et al. (Deeken CR et al. 2011) decellularized the central tendon of the porcine
diaphragm with several treatments but only 1% TnBP was effective in removing cell nuclei
while leaving the structure and composition of the tissue intact.
3. Cells
An important prerequisite for current tendon engineering is the successful isolation and
selection of functionally active cells, the cells have to retain the ability to proliferate rapidly
in vitro
to provide adequate numbers for
in vivo
implantation.
The most common cell types employed are fibroblasts, tenocytes and mesenchymal stem
cells/marrow stromal cells. (Doroski DM et al. 2007)
The main cell type found in tendon tissue is the fibroblast, which is responsible for secreting
and maintaining the extracellular matrix. Hence, fibroblasts are the predominant cell type
used for tissue engineering applications.
(Doroski DM et al. 2007)
Two different fibroblast populations can be found in the tendon: the elongated tenocytes
and the ovoid-shaped tenoblasts.(Li F et.al 2008)
Elongated tenocytes proliferate well in
culture and have optimal morphology in terms of expression of collagen type 1, which is a
major component of normal tendons.
(Li F et.al 2008)
Tendon cells are usually isolated from
