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In the United States, the most common tissue transplantations are bones, ligaments, tendons, heart valves, blood vessels, skin, and corneas transplantations.
Organ or tissue transplantation is a process in which an organ(such as a kidney) or a tissue (such as skin, bone, or a tendon) is taken from one person (donor) and inserted surgically into the body of another person (recipient).
Many organs and tissues can be transplanted. Donations include kidney, heart, skin, bones, tendons, or ligaments, etc. The need for donors is much greater than the actual number of donors in the world.
Some transplants such as – a liver transplant – are life-saving. Other transplantations like cornea (tissue covering the eye) do not save lives but help to restore eyesight.
The organs that can be donated are:
- Intestine
- Human Heart
- Lungs
- Kidneys
- Pancreas
- Liver
The tissues that can be donated are:
- Skin
- Connective tissues
- Bones
- Bone Marrows
- Heart valves
- Veins
Types of Transplantation
One of the greatest advances in medical science is Transplantation. It is a complex area of medical science. When an organ or tissue is transplanted, the recipients’ immune system may react unexpectedly. It may detect the tissue or organ as an invader and destroy it. To avoid this problem, the recipient needs a constant supply of immunosuppressant throughout their life.
Tissue Transplantation in the Same Person
When tissue is transplanted from one part of an individual to another part of the same individual, it is an autograft and the process is called autografting or autotransplantation. The risk of rejection is minimum.
- Skin Grafting: The process in which healthy skin is taken from a part of the body to heal a burned area or a wound on any other area of the body.
- Bone Marrow Grafting: The bone marrow of a person with cancer can be collected.
- Blood Vessels Grafting: For example, In Heart Bypass surgery, grafting provides another route for blood flow in a blocked vessel.
Tissue Transplantation from different people
- Allografting is a process in which a tissue is transplanted from one individual to another who are genetically non-identical individuals. Donor tissues can be taken from people who are alive or from those who died of a severe brain injury or lack of blood pump.
In Allografting, the recipients’ immune system may produce a response and reject the transplant. It may attack the tissue and destroy it. The allograft individuals have to take immunosuppression medicine to reduce the risk for the rest of their life.
- IsoGrafting is a transplant in which one tissue from a twin is transplanted to the body of another twin. The recipient’s immune system will never reject transplantation in this case. Both the twins must be monozygotic (genetically identical).
A transplant from other species
The grafting process in which a tissue is transplanted from another species (usually animals) into the human body is called xenografting. Faulty Heart valves of humans are transplanted and replaced with valves from a pig or a cow. In Xenografting, the recipients’ immune system rejects the donors’ tissue. Cytotoxic T cells identify it as an invading cell. They destroy the engrafted tissue: cytokines may also release macrophages to destroy the grafted tissue.
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Can You Get Sick from a Transplant?
The white blood cells present in the human body detect the transplanted organ as foreign invaders. Thus activating the immune system to fight against them. These cells destroy the recipients’ organs. This condition is called ‘’rejection’’. To avoid this situation, certain immunosuppressant medicines are given to the recipient. One huge drawback of this medication is that the body fails to fight against viral or bacterial infections.
In contrast to this, several tissue transplantations (connective tissues, blood vessels, bones) are not rejected by the body. As these tissues do not have any vascular system like organs, the human immune system does not recognize them as foreign invaders. Thus immune response is not generated and immunosuppressants are not needed.
Graft Versus Host Disease
Graft versus host disease (GVHD) is a rejection disease that occurs usually after an allotransplantation. GVHD occurs in the body of the recipient of a Bone Marrow Tissue Transplantation. GVHD causes a unique situation because the donors’ cell itself destroys the recipients’ cells or tissues.
There are two types of GVHD:
- Acute GVHD
- Chronic GVHD
Acute GVHD
The most important factor causing Acute GVHD is recipient/donor Human Leukocyte antigen mismatch. This difference in HLA causes the donor cell to recognize the recipient cell or tissue as an invading cell. This leads to an immune response that destroys the recipients’ tissues.
Acute GVHD may occur within a week after tissue grafting. It causes damage to recipients’ liver, gastrointestinal tract, eyes, and skin. Besides, acute GVHD may lead to a fatal condition of uncontrolled secretion of cytokine cells, called a cytokine storm.
Symptoms
- Yellowing of skin or eyes.
- Skin rashes or itchy skin.
- Diarrhea, vomiting, Nausea, or abdominal cramps.
Chronic GVHD
The exact mechanism causing chronic GVHD is not yet recognized. It is usually observed:
- In patients experiencing acute GVHD.
- In recipients having mismatched HLA transplantation.
The risk for the development of chronic GVHD is usually after months or years of stem cells/bone marrow transplantation.
Symptoms
- Skin rashes, decoloration, skin tightening.
- Shortness of breath, weight loss.
- Muscle fatigue or pain.
- Dry eyes, or Dry mouth, or Vaginal dryness.
- Abdominal cramps, difficulty in swallowing.
Who can be a Donor?
People of all ages can donate their organs or tissues. But the criteria may change depending upon the donors’ past medical history as well as age. The Organ Procurement Organization determines the eligibility for tissue or organ donation.
Future of Transplantation
The first successful transplantation was achieved in 1954, the transplantation has become a normal practice in recent years with the development of medical science.
Transplantation of non-self organs/tissues will soon become an out of date culture. Scientists are working on developing such methods by which new tissues or organs of an individual can be produced in vitro, using patients’ own harvested cells. Tissues or organs developed this way would contain patients’ own genetic material. Thus the recipient tissue or organ will not recognize them as invaders and no immune response is produced. This will reduce the rejection risk.
Modern methodologies
- 3D printing
- Inkjet bioprinting
- Microextrusion Bioprinting
- Laser-Assisted Bioprinting
- Tissue Engineering
