The donor might have recently died and donated heart, kidney, liver, bone, pancreas, etc. Living donors might also be used to donate lungs and kidneys. While transplantation technology has dramatically improved over the past several decades with the advent of anti-rejection drugs, the immediate problem is shortages in donor availability. For example, in 1998, there were 22,170 organ transplants in the U.S., but 4,855 patients died while waiting for suitable donor organs. Engineers and scientists have tried to create biomimetic devices and materials to replicate, augment or extend functions performed by biological systems.
Examples range from artificial hearts and valves to prosthetic hip and breast implants.
Many of these systems have had an enormous positive impact. Also, they do not behave physiologically like true organs or tissues. While all these therapies have had significant medical impact, there are newer technologies on the horizon which seek to overcome the limitations of these 'conventional' approaches. These newer approaches include harvesting tissues and organs from cloned transgenic animals and gene therapies. While cloning and gene therapy have received much publicity, there are still significant technical, economical, political and ethical issues which must be overcome before they become clinically available.