Organs for Transplant
Transplantation of a human kidney, heart, liver, pancreas, lung, and other organs is now possible due to two major breakthroughs. First, solutions have been developed that preserve donor organs for several hours. This made it possible for one young boy to undergo surgery for 16 hours, during which time he received five different organs. Second, rejection of transplanted organs is now prevented by immunosuppressive drugs; therefore, organs can be donated by unrelated individuals, living or dead. Even so, rejection is less likely to happen if the donor’s tissues “match” those of the recipient-that is, their cell surface molecules should be similar to one another. Living individuals can donate one kidney, a portion of their liver, and certainly bone marrow, which quickly regenerates. After death, it is still possible to give the “gift of life” to someone else-over 25 organs and tissues from the same person can be used for transplants at that time. A liver transplant, for example, can save the life of a child born with biliary atresia, a congenital defect in which the bile ducts do not form. Dr. Thomas Starzl, a pioneer in this field, reports a 90% chance of complete rehabilitation among children who survive a liver transplant. (He has also tried animal-to-human liver transplants, but so far, these have not been successful.) So many heart recipients are now alive and healthy that they have formed basketball and softball teams, demonstrating the normalcy of their lives after surgery.
One problem persists: The number of Americans waiting for organs now stands at over 80,000 and is getting larger by the day. Although it is possible for people to signify their willingness to donate organs at the time of their death, only a small percentage do so. Organ and tissue donors need only sign a donor card and carry it at all times. In many states, the back of the driver’s license acts as a donor card. Age is no drawback, but the donor should have been in good health prior to death.Organ and tissue donation does not interfere with funeral arrangements, and most religions do not object to the donation. Family members should know ahead of time about the desire to become a donor because they will be asked to sign permission papers at the time of death. Especially because so many Americans are waiting for organs and a chance for a normal life, researchers are trying to develop organs in the laboratory. Just a few years ago, scientists believed that transplant organs had to come from humans or other animals. Now, however, tissue engineering is demonstrating that it is possible to make some bioartificial organs-hybrids created from a combination of living cells and biodegradable polymers. Presently, labgrown hybrid tissues are on the market. For example, a product composed of skin cells growing on a polymer is used to temporarily cover the wounds of burn patients. Similarly, damaged cartilage can be replaced with a hybrid tissue produced after chondrocytes are harvested from a patient. Another connective tissue product made from fibroblasts and collagen is available to help heal deep wounds without scarring. Soon to come are a host of other products, including replacement corneas, heart valves, bladder valves, and breast tissue. The ultimate goal of tissue engineering is to produce fully functioning transplant organs in the laboratory. After nine years, a Harvard Medical School team headed by Anthony Atala has produced a working urinary bladder. After testing the bladder in laboratory animals, the Harvard group is ready to test it in humans whose own bladders have been damaged by accident or disease, or will not function properly due to a congenital birth defect. Another group of scientists has been able to grow arterial blood vessels in the laboratory. Tissue engineers are hopeful that they will one day produce more complex organs such as a liver or kidney.
Figure 1A Laboratory-produced bladder. This urinary bladder was made in the laboratory by tissue engineering.