Introduction Definition History Principle Cell sources What cells can be used? Scaffolds Biomaterials Bioreactor How tissue engineering is done? How does tissue engineering differ from cloning? Tissue engineering of specific structures Application of tissue engineering Limitations Conclusion References

1. By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. Contents:
 Introduction
 Definition
 History
 Principle
 Cell sources
 What cells can be used?
 Scaffolds
 Biomaterials
 Bioreactor
 How tissue engineering is done?
 How does tissue engineering differ from cloning?
 Tissue engineering of specific structures
 Application of tissue engineering
 Limitations
 Conclusion
 References

3. Introduction
 Tissue Engineering is a multidisciplinary field that applies
the principles of Biology, Chemistry, Physics and
Engineering for the development of substitutes that
replace, repair or enhance biological function of diseased
and damaged human body parts, by manipulating cells via
their extracellular microenvironment.

 Tissue Engineering is the study of the growth of new
connective tissues, or organs, from cells and a collagenous
scaffold to produce a fully functional organ for
implantation back into the donor host.

 This technique will allow organs to be grown from
implantation (rather than transplantation) and hence free
from imunological rejection.


4. Definition
 Broadly defined, tissue engineering is the
development and manipulation of laboratory-grown
molecules, cells, tissues and organs to replace or
support the function of defective or injured body parts.
 Or
 Technology combining genetic engineering of cells
with chemical engineering to create artificial organs
and tissues.


5. History
 Tissue engineering is a concept originally proposed by
American researchers in 1993, with the purpose of
using living cells to artificially grow tissue and organs
which would then be capable of carrying out their
normal functions.

6. Principle

7. Types of cells:
 Autologous: Harvested from patient
 Allogenic: Cells from donor
 Xenogenic: Cells from different species
 Syngeneic cells : which come from genetically
identical individuals

8. So what cells can be used?
 Cells used in tissue engineering have to be able to
divide in numerous times, so these cells are usually
stem cells.

 Stem cells are undifferentiated cells with the ability to
divide in culture and give rise to different forms of
specialized cells. Stem cells are divided into "adult"
and "embryonic" stem cells, the first class being
multipotent and the latter mostly pluripotent.

 Because stem cells have the ability to form specialized
cells, at the moment they are the best candidate for
tissue engineering .


9. Scaffolds
 Cells are often implanted or 'seeded' into an artificial
structure capable of supporting three-dimensional tissue
formation & to maintain the structure for tissue
formation.These structures, typically called scaffolds.
 Scaffolds must: Allow cell attachment and migration,
enable transportation of vital cell nutrients, and be
biodegradable.
 Stem cells are seeded into a scaffold.The scaffold is then
implanted into the correct position. A stimulus carried by
the scaffold triggers the cells to divide.The scaffold
provides nutrients and structure while the cells divide.The
scaffold biodegrades as the cells start to form a structure
strong enough to support itself.

11. Challenges
 In some cases, the scaffold will cause the
degeneration of surrounding tissues.


 Furthermore, scaffolds are many times rejected by
the immune system because it is recognized as a
foreign object

 The process retrieving of cells needed for tissue
engineering can also lead to tissue degeneration.


12. What can be done to overcome
these obstacles?
 The most promising solution to these obstacles is the SFF (Solid
Freeform) Scaffold.
 Scaffolds may also be constructed from natural materials: in
particular different derivatives of the extracellular matrix have
been studied to evaluate their ability to support cell growth.
Proteic materials, such as collagen or fibrin, and polysaccharidic
materials, like chitosan or glycosaminoglycans (GAGs), have all
proved suitable in terms of cell compatibility.
 The benefit of a collagen scaffold is that the body doesn’t reject
commonly reject it, the process doesn’t denature the collagen due
to high temperature, and offers the possibility of incorporating
biological molecules into the scaffold.


13. Biomaterials
 Many different materials (natural and synthetic,
biodegradable and permanent) have been
investigated.A commonly used synthetic material
is PLA - polylactic acid. This is a polyester which
degrades within the human body to form lactic
acid, a naturally occurring chemical which is easily
removed from the body. Similar materials are
polyglycolic acid (PGA) and polycaprolactone
(PCL): their degradation mechanism is similar to
that of PLA, but they exhibit respectively a faster
and a slower rate of degradation compared to PLA.

14.  Natural material:Extracellular Matrix (ECM)
Extarcellular gel-like substance which provides 3D
organization to cells and means of
communication,control of proliferation, cell
migration, attachment,differentiation and repair.
 The ideal biomaterial should be biocompatible in
that it is biodegradable and bioresorbable to
support the replacement of normal tissue without
inflammation.


15. Bioreactor
 A bioreactor in tissue engineering, as opposed to
industrial bioreactors, is a device that attempts to
simulate a physiological environment in order to
promote cell or tissue growth in vivo. A
physiological environment can consist of many
different parameters such as temperature and
oxygen or carbon dioxide concentration, but can
extend to all kinds of biological, chemical or
mechanical stimuli. Therefore, there are systems
that may include the application of forces or
stresses to the tissue or even of electrical current
in two- or three-dimensional setups.

16. How tissue engineering is done?

17. How does tissue engineering
differ from cloning?
 Human cloning is generally used to describe the
isolation of cells from an adult, and extraction of the
nucleus from one of these cells. This nucleus is then
injected into an embryonic cell and therefore all the
embryos derived from this will be identical to the
adult where the first cells are being isolated. This is in
sharp contrast to tissue engineering that aims at using
cells from human tissue - muscle, for example - to
regenerate another human tissue for the repair or
replacement of that tissue. While stem cells can be
used, they are not implanted into embryos, nor is the
goal of tissue engineering to reproduce an exact copy
of the "donor".

18. Tissue Engineering of Specific
Structures:
 BoneTissue Engineering:
Bone is a critical organ for prevention of injury and support of
normal functions (ambulation, mastication) and is the second
most transplanted tissue (after blood). Autologous bone tissue is
the preferred material for repair of tissue deficits that arise (from
trauma, disease, and birth defects) because the body is capable
of integrating with it, and remodeling it to an essentially normal
tissue.

19.  Kidney
 We applied the principles of both tissue engineering and
therapeutic cloning in an effort to produce genetically
identical renal tissue in a large animal model, cattle (Bos
taurus). Bovine skin fibroblasts from adult Holstein steers
were obtained by ear notch, and single donor cells were
isolated and microinjected into the perivitelline space of
donor enucleated oocytes (nuclear transfer).The resulting
blastocysts were implanted into progastrin-synchronized
recipients to allow for further in vivo growth. After 12 wk,
cloned renal cells were harvested, expanded in vitro, and
seeded onto biodegradable scaffolds.The constructs, which
consisted of the cells and the scaffolds, were then
implanted into the subcutaneous space of the same steer
from which the cells were cloned to allow for tissue growth.

20.  BloodVessels
 Tissue-engineered vascular grafts have been
constructed using autologous cells and
biodegradable scaffolds and have been applied in
dog and lamb models .The key advantage from the
use these autografts is that they degrade in vivo and
thus allow the new tissue to form without the long-
term presence of foreign material .

21.  Bladder
 Currently, gastrointestinal segments are commonly
used as tissues for bladder replacement or repair.
However, gastrointestinal tissues are designed to
absorb specific solutes, whereas bladder tissue is
designed for the excretion of solutes. Because of
the problems encountered with the use of
gastrointestinal segments, numerous investigators
have attempted alternative materials and tissues
for bladder replacement or repair.

22. Applications of tissue
engineering
 This technology is currently being used to treat
severely burned patients. A small sample of the
patient’s healthy skin is harvested, then grown and
transplanted to the burned areas. But while burn
patients have been benefiting from this type of
treatment for many years, improvements are still
needed to make the transplanted skin identical to
the original skin. Besides skin regeneration,
researchers have been working on a variety of
other applications for tissue engineering :

23.  Orthopedic:
 Vascular:
 Respiratory
 Ophthalmologic
 Constructing new organs, including liver and bladder
etc.

24. Limitations of traditional
tissue engineering approaches
 Despite these scientific progresses and clinical outcomes,
engineered tissues and especially thick or complex tissues still
suffer from reoccurring drawbacks:
 cell penetration and adhesion is not very effective.One or
several months might be needed for the cells to adhere and
proliferate into the scaffold.As a result, an incomplete
colonization, limited to the scaffold’s external layers may
occur.
 organs and tissues are generally complex, including
different cell types. Cell-to-cell contact and cell-to-substrate
interaction is critically involved in tissue morphogenesis and
regulation, or healing. Consequently the need to promote
cell-to-cell communication remains a very challenging issue
for this kind of approaches.

25. Conclusion:
 Tissue engineering is emerging as a vibrant industry
with a huge potential market.The biomaterials,
scaffolds, artificial organs, and differentiating cells
that are combined to create a tissue engineering
product address significant medical needs, such as
major tissue and organ damage or failure.Tissues
like muscle, skin, cardiac cells, nerve, bone,
cartilage have been regenerated by tissue
engineering approach and its application is being
extended for regenerating many more of such
tissues and organs.

26. References:
 Biotechnology-U.Satyanarayan.
 Net source: www.wikipedia.com
 www.kbiotech.com
 www.science.com