The Need for Replacement Body Parts

January 19, 2007

Humans don't have much capacity to regenerate their own body parts. So when disease or injury irreparably damages tissue or organs, doctors may need to find a replacement. Some parts can be replaced by man-made products, like artificial joints. Two commonly replaced joints are the hips and knees. The American Academy of Orthopaedic Surgeons report more than 638,000 hip and knee replacements were done in 2003.

Sometimes a machine can take over when a body part fails to function properly. In 2003, more than 324,800 Americans with end-stage kidney failure were receiving dialysis treatment. 197,000 people received heart pacemakers and 64,000 received implantable defibrillators.

When there is no artificial replacement part, or when a replacement part is not an ideal option, patients may be able to receive an organ or tissue transplant. The organization, Donate Life America, estimates 28,108 organ transplants and 1 million tissue transplants were performed last year in the U.S. Most transplants are taken from deceased donors. However, some living donors are able to give a kidney or a part of a liver to a transplant patient.

Limits of Replacements

Current methods of body part replacement are still far from perfect. Artificial joints can wear out or become loose or infected. Devices, like dialysis machines, can't completely take over all the function of the kidneys, and patients may still eventually need a transplant. Transplantation has its own limits. There aren't enough donor organs to meet the needs of potential recipients. Donate Life America estimates more than 91,000 Americans are currently on the transplant waiting list. About 18 people die each day because of a lack of available organs. Even if a suitable donor is found, transplant patients face a risk of organ rejection and must take immunosuppressant medication.

Tissue Engineering

So far, scientists haven't been able to develop body parts that are as good as the originals. But new technology may enable us to "grow" replacements using our own cells. Tissue engineering is the process of creating tissues outside the body and then implanting them in the body.

Tissue engineering technology has been used to create new "skin" for burn patients and others who require extensive or large skin grafts. Now the technology is being applied to the development of other tissues and organs as well.

One project is the creation of an artificial bladder. Anthony Atala, M.D., Director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine, has been successful in implanting lab-grown bladders into children and teens with spina bifida. In fact, this work has been named the Number 2 science story of the year by Discover magazine in the January 2007 issue.

George Christ, Ph.D., one of the Institute's Regenerative Medicine Researchers, explains the procedure. First, doctors take a small biopsy from the wall of the patient's bladder. Then cells are retrieved from the outside wall and from the inside wall. Scientists use genetic engineering techniques to make the cells grow and multiply into many times their original number. The process usually takes a few weeks to grow enough cells for their needs.

Next, the lab-grown cells are placed onto a biocompatible scaffold. The cells from the outside bladder wall are placed on one side of the scaffold and the inside cells are placed on the other side. Then, the cells and scaffold are placed in a machine called the bioreactor. Here, the cells continue to grow and mature into a "natural" bladder pouch.

Scientists have not yet been able to completely replace a diseased bladder. Instead, the lab-grown bladder was placed inside the diseased bladder to aid in natural bladder function.

The Wake Forest Institute for Regenerative Medicine is one of the largest facilities in the world researching tissue engineering and regenerative medicine. Researchers there are studying many other different tissue types as well. One project is developing new skeletal muscle. Hopefully, researchers can build and strengthen the muscle in the laboratory, then use it for wounded soldiers who've lost a significant amount of tissue. Another project is growing blood vessels to replace the vascular access in dialysis patients.

Christ says implanting tissues and organs made from a patient's own cells would help patients avoid the need for immune suppressing medication and, hopefully, provide a permanent fix for the problem.

For information on the program at Wake Forest University, visit http://www.wfirm.org/tissue_engineering.htm.

Copyright © 2007 by WSOCTV.com.

This article posted February 18, 2007.