The field of organ transplantation has made remarkable progress in a short period of time. Transplantation has evolved to become the treatment of choice for end-stage organ failure resulting from almost any of a wide variety of causes .

1. Organs and Tissues Transplantation
in Veterinary Medicine
By Layth Alkattan
2020

2. The field of organ transplantation has made
remarkable progress in a short period of time.
Transplantation has evolved to become the
treatment of choice for end-stage organ failure
resulting from almost any of a wide variety of
causes .
Transplantation of the kidney, liver,
pancreas, intestine, heart, and lungs has now
become common place in all parts of the world.

3. Definition:
Transplantation is the act of transferring an
organ, tissue, or cell from one place to
another. .

4. Types:
Broadly speaking, transplants are divided into
three categories based on the similarity
between the donor and the recipient:
1-Autotransplants
2-Allotransplants
3-Xenotransplants
.

5. 1-Autotransplants involve the transfer of tissue or
organs from one part of an individual to another
part of the same individual.
They are the most common type of transplants and
include skin grafts and vein grafts for bypasses.
NO immunosuppression is required

6. 2-Allotransplants involve transfer from one
individual to a different individual of the same
species—the most common scenario for most
solid organ transplants performed today.
Immunosuppression is required for allograft
recipients to prevent rejection.

7. 3- Xenotransplants involve transfer across species
barriers.
Given the complex, potent immunologic barriers to
success.

8. Transplantation Immunity
The success of transplants today is due in large part
to control of the rejection process.
Transplant antigen
The main antigens involved in triggering rejection
are coded for by a group of genes known as the
major histocompatibility complex (MHC).

9. Antigen initiate rejection and graft damage, via humoral
or cellular mechanisms:
Humoral rejection mediated by recepient's AB. (e.g.
blood transfusion, previous transplant, or pregnancy)
Cellular rejection is the more common type of rejection
after organ transplants. Mediated by T lymphocytes, it
results from their activation and proliferation after
exposure to donor MHC molecules.

10. Complications of Organ Transplantation
1- Rejection
2-Malignancy

11. Clinical Rejection:
Graft rejection is a complex process involving several
components, including T lymphocytes , B lymphocytes,
macrophages, and cytokines, with resultant local
inflammatory injury and graft damage.
Rejection can be classified into the following types based on
timing and pathogenesis: hyperacute, acute, and chronic.

12. A-Hyperacute rejection:
This type of rejection, which usually occurs
within min after the transplanted organ is
reperfused, is because of the presence of
preformed antibodies in the recipient,
antibodies that are specific to the donor.
The result is a swollen, darkened graft, which
undergoes ischemic necrosis.

13. B-Acute rejection:
This used to be the most common type of rejection, but with
modern immunosuppression it is becoming less and less
common.
Acute rejection is usually seen within days to a few months
post transplant. It is predominantly a cell-mediated process,
with lymphocytes being the main cells involved.
With current immunosuppressive drugs, most acute rejection
episodes are generally asymptomatic.

14. C-Chronic rejection:
This form of rejection occurs months to years post
transplant.
Histologically, the process is characterized by atrophy,
fibrosis, and arteriosclerosis.
Both immune and nonimmune mechanisms are likely
involved.
Clinically, graft function slowly deteriorates over
months to years

15. Clinical immunosuppression
The success of modern transplantation is in large part
because of the successful development of effective
immunosuppressive agents.
Two types of immunosuppression are used in
transplantation: Induction and Maintenance
immunosuppression.

16. 1-Induction immunosuppression
Refers to the drugs administered immediately
during transplant to induce immunosuppression.
Biologic agents (monoclonal and polyclonal
antibodies) consist of antibody preparations

17. 2-Maintenance immunosuppression
Refers to the drugs administered to maintain
immunosuppression once recipients have recovered
from the operative procedure.
. Nonbiologic agents (e.g. corticosteroids, azathioprine
)form the mainstay of maintenance protocols.

18. 2-Malignancy:
Transplant recipients are at increased risk for
developing certain types of de novo malignancies,
including
1. Non melanomatous skin cancers.
2. Lymphoproliferative disease.
3. Gynecologic and urologic cancers

19. Sources of organs for transpalntation:
The current Main Sources of organs for
transpalntation are:
1-Deceased (cadaver) donor (however the recipient
has to wait till this cadaver becomes available)
2-Living donor transplantation (has medical,
ethical, financial, and psychosocial problems).

20. New directions for organ Transplantation:
Stem Cells
,
Cell Therapy
And
Tissue Engineering

21. Cell therapy can be defined as «The use of living cells to
restore, maintain or enhance the function of tissues
and organs».
The use of isolated, viable cells has emerged as an
experimental therapeutic tool in the past decade. Now
due to progress in cell biology and particularly in
techniques for the isolation and culture of cells derived
from several organs and tissues, thus the cell therapy
became available

22. Cell-based therapy is one of the more recent
approaches in regenerative medicine that aims
at replacing or repairing organs and tissues.
Different cell types have been used, such as
skeletal myocytes, which have been injected
into infarcted cardiac scar tissue, or neuronal
cells inoculated into the brains of animal with
nervous disorders.
Alternative approaches include extracorporeal
organ replacement for kidney and liver failure

23. Forms (types) of cell therapy:
1-Extracorporeal bioartificial organs used as assistance
devices.
2-Injections, implantations or transplantation of cells.

24. Cell sourcing remains among the most critical
difficulties in the development of cell
therapies, whether for bioartificial organs or
for cell transplantation.
This problem could be alleviated by use of
stem cells (this is called stem cell therapy),
especially probably in combination with
grafting methods

25. Stem cells
 Stem cells are cells that have the ability to
continuously divide to generate exact copies of
themselves in a process called self-renewal and the
ability to change into specialized cells in a process
called differentiation.

26. stem cell?
Differentiation is the process by which an unspecialised cell
acquires the features of a specialized cell such as a heart,
liver, or muscle cell.
This process is controlled by the interaction of a cell's genes
with the physical and chemical conditions outside the cell,
usually through signaling pathways involving proteins
embedded in the cell surface.

27.  Embryonic stem cells are undifferentiated cells
derived from a pre-implantation embryo which
have the potential to differentiate into many
different types of cells, i.e. they are pluripotent.
 Tissue stem cells (sometimes referred to as
adult or somatic stem cells) can give rise to at
least one specialized (differentiated) cell-type.

28. Stem cells have 4 main properties:
1-Unspecialized.
2- Self renewal.
3-Potency :Stem cells are either:
Totipotent (e.g. fertilized ova).
Pluripotent(e.g. ES cells.)
Multipotent (e.g. tissue stem cells).
Unipotent (e.g. hepatocytes, skin and corneal
stem cells).
4-repopulation (functional, long term tissue
reconstitution).

29. Stem cell therapy
 means treatment in which stem cells are induced to differentiate
into the specific cell type required to repair damaged tissues.
 Right now, only few diseases are treatable with stem cell
therapies because scientists can only regenerate few types of
tissues.
 stem cell types - including bone marrow-, umbilical cord-, and
fetal liver-derived hematopoietic stem cells, mesenchymal stem
cells (MSCs), renal adult stem cells, and neural stem cells - have
been used

31. Tissue engineering
1. Tissue engineering is the process of creating living, physiological
3D tissues and organs.
2. The process starts with a source of cells derived from an animals
or from a donor.
3. The cells may be immature cells, in the stem cell stage, or cells
that are already capable of carrying out tissue functions; often, a
mixture of different cell types (e.g., liver cells and blood vessel
cells) and cell maturity levels is needed.

32.  Tissue engineering is the use of a combination of cells,
engineering and materials methods, and suitable
biochemical and physicochemical factors to improve or
replace biological tissues.
 Tissue engineering involves the use of a tissue scaffold
for the formation of new viable tissue for a medical
purpose.
 Tissue engineering has also been defined as
"understanding the principles of tissue growth, and
applying this to produce functional replacement tissue
for clinical use
 The term has also been applied to efforts to perform
specific biochemical functions using cells within an
artificially-created support system (e.g. an artificial
pancreas, or a bio artificial liver).

33. The materials used for tissue engineering are either
Synthetic biodegradable materials
polylactic acid (PLA), polyglycolic acid (PGA), poly lactic-
glycolic acid (PLGA), polypropylene fumarate, poly ethylene
glycol (PEG) and polyarylates)
Natural materials
collagen, hydroxyapatite, calcium carbonate, and alginate.
Natural materials are typically more favorable to cell
adherence, whereas the properties of synthetic materials such
as degradation rate, mechanical properties, structure, and
porosity can be better controlled

34. Open tissue engineering systems
have been successfully used to create a number of
biological substitutes such as bone, cartilage,
blood vessels, cardiac, smooth muscle, pancreatic,
liver, tooth, retina, and skin tissues.
Closed tissue engineering systems have been used
particularly for the treatment of diabetes, liver
failure, and Parkinson’s disease