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Education: Transplantation

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Transplantation

Transplantation is a surgical procedure in which cells/tissue/organ is transferred from a donor to a recipient or from one part of the body to another.  Heart, lung, liver, kidney, cornea, bone marrow, hand and facial tissue transplants are performed to treat life-threatening and disfiguring illness.

Allotransplant

is when a transplant is performed from a donor that is genetically non-identical but from the same species as the recipient. Most heart, lung, liver, kidney, cornea, bone marrow, hand and face transplants are allotransplants.

Xenotransplant

is when transplant is performed from a donor that is from another species as the recipient. For example if a heart of liver from a pig or baboon is transplanted to a human.

Isotransplant

is when a transplant is performed between genetically identical twins.

Autotransplant

is when cells, tissue or an organ is transplanted from one site to another on the same human or animal. For example when a toe from the foot is transplanted to the hand to replace an amputated finger.

Composite Tissue Allotransplant (CTA)

is when a composite of several different tissues are transplanted from a donor that is genetically non-identical but from the same species to a recipient. Examples of CTAs are hand and face transplants that are made up of a composite of skin, muscle, bone, nerves, blood vessels, etc…

Rejection

In most allotransplants the recipient’s immune system will identify transplanted cells/tissue/organs as being foreign and will attempt to reject them/it. Therefore, transplant recipients must take life-long medications to suppress their immune system (immunosuppression) and prevent rejection.

Graft-versus-host disease

When allotransplanted cells/tissue/organ attempt to reject the recipient.

Organ Transplants

A team in Boston, USA in 1954, performed the first successful organ transplant in humans. The team transplanted a kidney between 23-year-old Ronald and Richard Herrick, who were identical twins. Today more than 400,000 kidney transplants have been performed worldwide and heart, liver, lungs, pancreas, and intestine are transplanted routinely.

Tissue Transplants

In addition to solid organs, bone marrow cells and other tissues can also be transplanted from one individual "donor" to another "recipient". Bone marrow transplants consist of transplanting health bone marrow cells from a donor to a recipient whose marrow cells have cancer "leukemia". One or several tissues together "composite tissue" can be transplanted from a brain dead donor to a recipient to reconstruct missing body parts (hand and facial tissue transplants). Tissues transplanted in the clinical setting on a routine basis include: bone, tendon, cornea, skin, heart valves, and veins.

Organ/Tissue Donation

Organs and tissues are donated by living, or brain dead donors and must be harvested within 24 hours of cessation of the donors heartbeat. Unlike organs, most tissues (with the exception of corneas) can be preserved and stored, or "banked" for up to five years.

Organs and Tissues for Donation
(Source: http://www.donatelifeny.org/)

Composite Tissue Allotransplantation

Composite tissue allotransplantation (CTA) is the transplant of a composite of different tissues (skin + bone + muscle, etc) from one a donor to a recipient and has taken a lot longer than  organ transplants to be used clinically. One of the main reasons for this is because CTA's like hand and facial tissue contained skin tissue which is is much more immunogenic than other organs. Accordingly the medications being used successfully to prevent organs from rejecting were not sufficiently strong enough to prevent skin from rejecting. In late 1990's a team of researchers in Louisville, USA (See timeline) demonstrated that combining a cocktail of 3 different immunosuppression medications effectively prevented skin rejection. This landmark finding made it possible for teams around the world to begin transplanting hands and facial tissue.

Composite Tissue Allotransplantation History Timeline
(Source: Whitaker IS, eta., JPRAS. (2008);61(5):481-92)

 

Hand Transplants

In 1998 a team in Lyon, France performed the first successful human hand transplant. For a detailed account of the research and events leading to the first human hand transplants see:

Facial Tissue Transplants

In 2005 the first human facial tissue transplant was performed by a team in Amiens, France.

For a detailed account of the research and events leading to the first human face transplants see:

Immunosuppression

In order to prevent the donor’s transplanted organ or tissue from being rejected the recipient must take strong immunosuppression medications for life. These medications that prevent rejection can be toxic and cause many unwanted side effects. For this reason the benefits of receiving a transplanted organ or tissue must be carefully balance with the risks posed by having to take these medications for life. While stronger and less toxic immunosuppression medications are being developed all the time, still immunosuppression continues to be the single greatest drawback in transplantation.

Focus of our Current Research

With the above drawback in mind the focus of current research in organ and tissue transplantation is to eliminate the need for using these toxic medications. One such approach, known as "tolerance", attempts is to manipulate the recipient’s immune system so that it selectively does not reject the transplanted organ/tissue. Another approach is to use methods of regenerative medicine/tissue engineering, in which case the organism’s own inherent ability to regenerate and renew cells and tissue is manipulated to regrow tissues. This latter approach is the focus of the research being conducted at the Frankfurt Initiative for Regenerative Medicine (FIRM).

Helpful related Links

For more information on the history and science of organ and tissue transplantation the reader is directed to hand and face transplant research on this website and to the following websites:

History of Transplantation: http://www.organtransplants.org/understanding/history/index.html

Wikipedia-Organ Transplantation: http://en.wikipedia.org/wiki/Organ_transplantation

New York Organ Donor Network: http://www.donatelifeny.org/all-about-transplantation/