Biomedical Engineering Reference
In-Depth Information
human tendon samples by tissue dissociation techniques.(Bagnaninchi PO et al. 2007) (Yao L
et al 2006) (Cao D et al 2006)
After two or three cell culture passages and before they lose their phenotype, they are
seeded into collagen gels or into scaffolds at an appropriate cell density (10
6
cells/mL).
(Bagnaninchi PO et al. 2007) (Yao L et al 2006) (Cao D et al 2006)
Anyway the use of tenocytes have some drawbacks such as limited availability of donor
sites for cell harvest, the requirement for lengthy
in vitro
culture to expand the number of
cells, and donor-site morbidity limit the practicality of this technique. (Hankemeier S et al.
2005) (Awad HA et al. 2000)
Stem cells may represent the ideal source for tendon engineering.There are 2 types of stem
cells: embryonic stem cells and adult stem cells, embryonic cells are totipotent, but their
practical use may be limited because of ethical issues and concerns regarding cell regulation.
Adult stem cells, also known as mesenchymal stem cells, show excellent regenerative
capacity, the ability to proliferate rapidly in culture, and the ability to differentiate into a
wide variety of cell types.( Gao J and Caplan AI 2003) (Alhadlaq A & Mao JJ 2004)
(Bosnakovski D et al. 2005) (Grove JE et al. 2004)
The ability of human marrow derived adult mesenchymal stem cells that have tendinogenic
differentiation already has been documented in several studies: mesenchymal stem cells can
be stimulated to differentiate into fibroblasts when exposed to mechanical stress, (Ge Z et al.
2005)
and their rates of proliferation and collagen excretion have been shown to be higher
than those of fibroblasts, so they may be a viable alternative to fibroblasts.
(Li F et.al 2008)
The ideal source of autologous stem cells would be one that is easy to obtain, results in
minimal patient discomfort, and provides cell numbers substantial enough to obviate
extensive expansion in culture.
Studies have shown that raw adipose tissue contains a population of adult stem cells that
can differentiate into bone, fat, cartilage, or muscle in vitro.( Lee RH et al. 2004) (Zuk PA et
al. 2001) (Lee JA et al. 2003)
These adipose-derived stem cells are easily accessible and unlike marrow are available in
large quantities with acceptable morbidity and discomfort associated with their harvest.
The autologous nature of these stem cells together with their putative multipotentiality and
ease of procurement may make these cells an excellent choice for many future tendon-
engineering strategies and cell-based therapies.( Young RG et al. 1998)
Tissues treated with these cells showed a markedly larger crosssectional area and contained
collagen fibers that were better aligned than those in matched controls. (Awad HA et al.
1999)
Compared with their matched controls the MSC-mediated repair tissue showed marked
increases in maximum stress, modulus, and strain energy density. Morphometrically,there
were no marked differences in microstructure between the experimental and the control sides.
Kryger et al.( Kryger et al. 2007) compared tenocytes and mesenchymal stem cells for use in
flexor tendon tissue engineering. They studied four candidate cell types for use in reseeding
acellularised tendon constructs. Specifically, they compared epitenon tenocytes, tendon
sheath fibroblasts, bone marrow-derived mesenchymal stem cells (BMSCs), and
adipoderived mesenchymal stem cells (ASCs) with respect to their in vitro growth
characteristics, senescence and collagen production, as well as the viability of reseeded
constructs.( Kryger et al. 2007) They also studied the in vitro viability of tendon constructs
after reseeding and after
in vivo
implantation in a clinically relevant model of rabbit flexor
tendon grafting. Results showed that epitenon tenocytes, tendon sheath cells, bone marrow
