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Engineering, 2012, 5, 43-45
doi:10.4236/eng.2012.410B011 Published Online October 2012 (http://www.SciRP.org/journal/eng)
Copyright © 2012 SciRes. ENG
Tissue Engineering: From Bench to Bed Side Exemples of
J-F. Stoltz1,2, C. Huselstein1, D. Bensoussan1, N. de Isla1, V. Decot 1
1CNRS UMR 7561, Biopôle, Fa cul té de M édec ine – Universi té Lorraine, VANDOEUVRE LES NANCY, Fran ce
2CHU de Nancy, UTCT, Braboi s , VANDOE UVRE LES NANCY, Fran ce
Tissue engineering is an emerging multidisciplinary field involving surgery medicine, biology, chemistry, mechanics and engineering
to improve the health and quality of life by restoring, maintaining or enhancing tissue and organ functions [6;11]. The principle is
simple: cells are coll ected and introduced -with or without modification of their biological properties- into an environment in which
physico-chemical and mechanical parameters are kept stable. When they reach maturity, the biotissue or cells can be grafted. The
main parameters are: cells, scaffold, biological molecules and mechanical forces. A combination of these parameters can promote
cellular differentiation and proliferation. But it should be emphasized that at this time, signalling pathways and the rationale behind
the physiological design remain to be elucidated. Among the main medium-term clinical applications are cardiac insufficiency,
atherosclerosis, osteoarthritis, diabetes, liver diseases, bladder, and skin. In this paper the examples of cartilage and vascular engi-
neering will be exa min ed.
Keywords: Tissue Engineering; Stem Cells; Scaffolds
1. How to Choose the Cells
It seems best to choose auto logous cells. But th ese cells are n ot
easily available and are frequently in a pathological state. This
explains the increasing interest in the use of undifferentiated
progenitor cells which have ability to proliferate and differenti-
ate int o the target t issue. There ar e differen t types o f stem cells
(SC), which are characterised by their functional properties.
After fertilisation, the egg divides into two, four and eight cells
or identical blastomers. At the 16-cell stage, the embryo is
made up of t wo extern al an d in tern al cel l t ypes. Throughout the
development of the embryo, then of the fœtus and finally in the
adult, different stem cells with different potential can be iso-
lated and characterised: totipotent SC: up to the 8-blastomer
stage. These cells are capable of in ducing embryonic an d fœtal
development; pluripotent SC isolated from the morula, 16-32
cells and pluripotent SC isolated from the blastocyst. Embry-
onic cells are totipotent and theoretically have an unlimited life
span. However, there is some controversy about using these
cells due to their origin and procurement. Further more, they are
affected by potential immunogenicity and tumorigenic trans-
formation. In the fœtus, some stem cells circulate and can be
isolated from the umbilical cord.
A particular case is that of the mesenchymal stem cell s (MSC)
isolated from different tissues (bone marrow, adipose tissue,
umbilical cord, (Wharton Jelly) whose properties are similar to
that of pluripotency [1,2,5,10]. Their physiological roles are
concerned by their regenerative ability of injured tissue. They
have been the subject of increasing attention in regenerative
medicine thanks to their ability to differentiate into numerous
cells lineages. Today, bone marrow is the most frequently used
source of MSC, but it has been demonstrated that the number of
MSC decrease with the donor’s age. For this reason, research-
ers identified alternative sources of extra-embryonic cells (foe-
tal cord, amniotic membrane, placenta, etc.). To create distinct
types of tissue from stem cells, control of the induction and
maintenance of cell differentiation is indispensable.
Tissue engineering scaffolds are designed to provide a three-
dimensional environment to support and direct cellular proc-
esses in their migration, proliferation, and differentiation to-
ward a functional tissue. The scaffold provides mechanical
stability and the required surface chemistry to orchestrate bio-
logical signals and influence cellular adhesion and function.
Scaffolds must be biocompatible; sufficiently porous to allow
nutrients to reach cells and ultimately degrade during biotissue
development without toxi c ef fects (s ee Table 1 below).
Table 1. Examples of available scaffolds for tissue Engineering (non
exhaustive) (*scaffo lds used by the authors in their researches).
Natural Polymers Synthe tic Polym er s
Hyaluronic Acid (HA)*
Sodium Alginate *
Cho ndr oi ti n sulfate
Type I Collagen*
Poly (α-hydroxyl esters) (PLA,
PGA and PLGA)*
Poly (ethylen glycol/oxide )
Poly - L - lysine (PLL)*
Poly (propylen fumarate)
Poly (vinyl alcohol)
J-F. STOLTZ ET AL.
Copyright © 2012 SciRes. ENG
Various ways have been explored for the development of
3-D scaffolds that will interact with cells. Biological scaffolds
include collagen, alginate, hyaluronic acid, and polyelectrolyte
fil ms [8,9,13]. These scaffolds could allow better regulation of
cell adhesion and matrix production by resident cells. However,
biological scaffolds have a higher risk of contamination or im-
mune reaction than synthetic scaffolds. On the other hand, syn-
thetic materials, which are created de novo from molecules
such as glycolic acid or lactic acid polymers, allow more pre-
cise control of both structural and mechanical p roper ties, an d of
rates of resorption. Different kinds of hydrogels have been used
for biomedical applications. Their water-swelling structure
enables the time-dependent release or incorporation of water
molecules in the outer environment. Alginates and polymers are
widely employed and are very easy to use in cartilage engi-
neering. However, few investigations have considered the or-
ganization of a tissue as a basis for the development of strati-
fied tissu es (e.g., cartilage, bl ood vessels). Fro m this viewpoint,
complex 3-D structures of a biotissue could a priori be built
layer by layer using different components [9,12]. However, up
to now, few methods that can efficiently synthesize stratified
structures, including viable specific cells interacting with a
biofunctionalized environment have been proposed. One exam-
ple, we recently developed, is the construction of a stratified
scaffold seeded with chondrocytes or SC by spraying. The stra-
tified scaffold was constructed of layers of alginate / HA
welded by polycation / polyanion (Poly-L-Lysine / HA) .
This new method allows the use of a 3D structure, which is
important for chondrogenic induction of MSC with no growth
factor, but also the construction of a stratified scaffold. The
result is an innovative configuration that mimics the structure
of cartilage. We clearly demonstrated that the sprayed bioma-
terial no t on ly keep s th e mech an ical p ro p erties need ed for cell s,
but also maintai ns the cell ph en otype and th e cap acity to i ndu ce
bio cartilage. This original strategy could be used to design new
stratified engineered tissues through progressive cells and hy-
drogel, with alternate layers sprayed with polyelectrolyte to
weld the layers together. The spraying process helps form a
highly functional and s tr uc ture d b i oti ss ue s .
3. Influence o f Mechani ca l Forc es
All cells and tissues are subject to mechanical stresses .
These forces have various origins, from pressure forces linked
to gravity, to motion forces (i.e., blood circulation, loading on
cartilage and bone during movement). Their force ranges from
a few Pascals on the vascular wall (shear stress) to several
mega-Pascals on hip cartilage. It is now accepted that these
forces are likely to modify cellular behaviour by affecting dif-
ferentiation, metabolism, matrix production, paracrine or
autocrine factor secretions, gene expression, etc. (concepts of
mechanobiology and mechanotransduction). Such is the case
for chondrocytes, bone cells, smooth muscle cells and vascular
endothelial cells. However, although the physiological effects
of stress are now well known, the steps leading from the me-
chanical signal to physiological responses and gene expression
remain to be elucidated. Various hypotheses have been pro-
posed but none is consistent with the bulk o f experi mental d ata.
Most attempts to locate potential mechanotransducers have
focused on two main structures of the cell: the membrane and
the cytoskeleton, because forces act directly on the membrane
and b ecaus e the force ap pl ied is transmitted to th e cytoskeleton.
But it is likel y that a cell u ses a variety of mechano transd uctio n
pathways depending on the type of physiological change in-
duced, which makes interpretation difficult. In “biotissue” pro-
duction, dynamic mechanical stresses on cells generally pro-
mote differentiation and increased matrix production.
4. Cell Preparation and Engineering Approaches
After choosing the cells, multiplication and differentiation in
cultu re and/or in the scaffold ar e requ ired. Thu s, it is necessar y
to dispose of culture media whose composition, specific growth
factors, etc., are compatible with the cells of interest and with a
GMP process. A variety of proteins can affect cell differentia-
tion and phenotypic expression, including transforming growth
factor TGF-β, insulin-like growth factor (IGF-1), bone
morphogenetic proteins (BMPs), fibroblast growth factors
(FGFs), VEGF and epidermal growth factor (EGF). These
molecules have a broad range of activities, including prolifera-
tion induction, differentiation and increasing the synthesis of
the extracellular matrix components by the cells. For example
transforming the growth factor (TGF-β) superfamily, including
TGF-βs 1-3 and insulin-like growth factor-1 (IGF-1), stimulate
GAG synthesis by chondrocyte when collagen II is strongly
stimulated by IGF-1. It has also been demonstrated that MSC
cultu res expo sed to TGF-βs show increased cell density, cluster
formation, glycosaminoglycan and type II collagen synthesis.
5. Grafting and Safety Studies: Respect of
One other problem to be solved is the local implantation (with
or without scaffold). It is important to note that clinical applica-
tions of biotherapies are strictly controlled in Western countries.
Cells or tissues of human origin can only be harvested in healt h
centres accredited by Public Authorities (In France, different
laws concern the authorization procedure related to the prepara-
tion, storage and clinical use of cells and tissues). The European
Regulating Authorities are also very strict about the nature of
the clinical trials and the choice of the patient.
Before grafting, different points need to be clarifed:
- What type of grafting is planned for the patients? (What is
the degree of severity of the pathology to consider, grafting in
the early phase of the pathology or after stabilization? (i.e.,
myocardi al infarction)
- Has the grafting site been identified or not?
- What are the benefits for the patient?
- Clinical evaluation: this is a crucial step which must vali-
date the graft through studies of total or partial tissue restora-
- Is immunosuppression needed and what are the possible
6. Main Potential Clinical Applocations
Biotissus based on stem cells have many possible applications
in biology, in pharmacology, and hopefully in tissue engineer-
ing. The hop es concern the majori ty of the medical specialities,
J-F. STOLTZ ET AL.
Copyright © 2012 SciRes. E NG
but different applications can be envisaged in the coming dec-
ade. In presentation different applications are presented (carti-
lage, bone, blood vessel, heart, li ver, bladd er reparation, etc.).
The regeneration of tissues is and will remain a challenge for
the further development of cell therapy and tissue engineering.
Adult stem cells and in particular mesenchymal SC should
enable exciting developments in regenerative medicine. How-
ever, many probl ems remain to be solved:
- The lack of scien ti fic an d t echn ical kn owled ge which co ul d
enable the development of innovative strategies (quality of the
cells and their role in producing tissue repair, properties of the
synthes ized matrix, import ance of mechanical s ignal, etc.)
- How can we increase the yield resulting from the prep ara-
tion of the differentiated stem cells and advance our knowledge
of the heterogeneous character of the preparations.
- to the need for a standardised reproducible product. The
use of mesenchymal SC of Wharton’s jelly seems to be an in-
teresting possibility to prepare controlled batches of stem cells
for the future.
- Technical problems regarding the definition of scaffolds,
the cells used and long term stability and culture medium. In
particular, the impact of the biomaterial used remains to be
- Grafting: biotissue can be introduced via direct cell im-
plantation (cell therapy), biotissue transplantation or gene ther-
- Risk of teratogenic effects and of immune reaction (the
immune risk is lowest using stem cells from the umbilical
- Religiou s and legal issu es concernin g the different national
Current knowledge allows us to be optimistic about the fu-
ture of tissue engineer in g and cell t her apy bu t final ans wers c an
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