November 19, 1999

Series: Keeping future in sight key to Transplant Center’s success

Featured Image

During a recent follow-up examination, Dr. Kenneth Johnson checked the flexibility of patient Juanita Davis’ “new” ankle, which was replaced with a prosthesis like the one pictured below. (photos by Dana Johnson)

Series: Keeping future in sight key to Transplant Center's success

For the past 10 years, Vanderbilt University Medical Center has housed one of the nation's top transplant programs.

The Transplant Center is a comprehensive program that is unique in its operation — all of its services are located in one facility. This arrangement allows physicians and patients to share in the educational, research and clinical options available through the programs offered at the site.

Despite the collaborative efforts of the many transplant programs, the director of the center said there is still one problem that faces the multidisciplinary team — how to increase the number of donor organs available for transplantation.

"Our biggest problem is not how to do transplants better," said Dr. J. Harold Helderman, Professor of Medicine, Professor of Microbiology and Immunology and Medical Director of the Transplant Center. "But that we have so few organs.

"We perform transplants well and we can only make small improvements there. In the future there is a great deal of research directed at finding ways to improve the organ supply in sociopolitical ways and through xeno transplantation."

Helderman said that organ transplantation coupled with a concrete understanding of the immune system process and improved anti-rejection medications, has become very successful as a standard approach in the management of failed internal organs.

For now much attention has been focused on xeno transplantation and the possibility it brings to creating a whole new field of organs available for human transplantation. It also brings a host of challenges.

"Xeno transplantation is very promising, but it will take a lot of work," admits Dr. Richard Norris Pierson III, assistant professor of cardiac and thoracic surgery. "We need to get to where it's not of high cost to the patient. It's expensive physiologically. The anti-rejection drugs are very powerful and have a number of side effects.

"We are working on finding tricks to fool the immune system to make xenotransplantation successful. It's a formidable challenge."

The problems researchers face while developing this type of transplantation include hyperacute rejection, accelerated vascular rejection and the possibility of pig organs transmitting viruses and other diseases to human recipients.

"We are working on solutions to all of these," Pierson said. "We are testing both the heart and the lung from transgenetic pigs.

"It is technically possible to sew one of these organs into a patient today and the patient could survive for a couple of months, but the questions still exist when will it be appropriate and in which patients."

Pierson said many transplant and research experts are split on the subject. Some say the procedure should already be in use. Others say, as an alternative treatment, the potential is there for use in the first decade of the 21st century.

But while many in the field question the readiness of such transplant procedures, the fact remains that without a formidable anti-rejection medication, it's a mute point.

Helderman once wrote in an editorial review that the history of solid organ transplantation could be described as the function of the anti-rejection medications that were available. Now there are so many drugs available that the medical personnel are not sure how to use them yet.

He describes the history of anti-rejection drugs that began as experimentation in 1954. Nearly 40 years later the discovery of Imuran, a Nobel Prize winner, allowed for the transplantation of cadaver kidneys with a 50 percent success rate. In 1983 the introduction of Cyclosporin. This drug's effectiveness made the kidney transplant the renal replacement of choice over dialysis. It also boosted the success rates of heart, liver, lung and pancreas transplants. And today we use designer drugs, which allows for different drug combinations for the best outcome.

"We now have so many options that the strategy of transplantation has changed," said Helderman. "Any size no longer fits all. There are many new agents. Now we are trying to figure out what drugs work best for a given patient with the least side effects."

There are three views of the future of transplantation. The first vision involves xeno transplantation; the second places emphasis on learning how to induce total tolerance for a new organ, which eradicates the need for anti-rejection medications and the third vision calls for the continued use of anti-rejection medications with lower side effects and toxicity levels.

"The first two ideas are laudatory, but are not attainable in the next 10 years, said Helderman. "The third vision is the one I take. It's how we practice now. We all hope, dream and pray for the first two to occur, but we don't expect them soon."