Other Organ and Tissue Sources

Other Organ and Tissue sources
In addition to organs donated from humans, researchers are exploring the use of partially or wholly artificial organs manufactured in the laboratory. The use of organs from other species of mammals, a technique called xenotransplantation, is also being researched.


Artificial Organs and Tissues
One way to get around the shortage of donors is to use wholly or partially artificial organs made of plastic, metal, and other synthetic materials. A kidney dialysis machine, for example, is an artificial organ, even if it is too large to implant in the body.

In 1982 American physician William DeVries implanted a crude artificial heart into the chest of dentist Barney Clark. But Clark survived for only 112 days and the heart itself, powered by an air pump that required its own cart, proved impractical.

Although subsequent researchers have built smaller, more efficient hearts, none of these devices have proved successful. Instead, emphasis has shifted to the use of left-ventricular assist devices (LVADs), which are implanted beside a patient’s heart to help it pump blood. LVADs keep patients alive until a donor heart is available.
Many artificial devices work to restore the operation of malfunctioning organs without replacing the whole organ. Examples include artificial heart valves and pacemakers to help the heart function properly, and cochlear implants to restore hearing.

Other researchers are working to build replacement organs and tissues from human cells, a technique known as tissue engineering. The Food and Drug Administration (FDA) has approved two types of artificial skin made by growing a relatively small number of human skin cells on an artificial surface in the laboratory.

The cells multiply and grow into a useful skin covering that can be used to cover larger areas than are possible with a simple autograft. Researchers hope to develop other types of artificial organs as well, such as artificial pancreases in which insulin-secreting pancreatic cells are enclosed in a porous membrane that enables nutrients, but not immune cells, to reach the cells while insulin diffuses out.

Some scientists hope to use embryonic stem cells, which are found in very early stage human embryos and are capable of developing into almost any type of cell in the body, to overcome the shortage of donor organs. If researchers learn how to make embryonic stem cells develop into specific tissues, the cells could be used to produce new organs or to repair organs, such as the heart, that cannot regenerate.