Physicians at the New York University/Langone Transplant Center New York announced last week that they had successfully transplanted a pig kidney into a human. The recipient was a brain dead victim of a brain tumor. The kidney had been functioning and appeared to be normal for more than 30 days since it was removed from the pig donor and placed in the human recipient. The recipient’s kidneys had been removed, thereby making his ‘survival’ entirely dependent upon the transplanted pig kidney.
Prior efforts at transplanting organs from animals to humans had been somewhat successful for brief intervals, but no team had previously had success with a kidney from a nonhuman that continued to function normally and effectively for more than a month. The kidney was taken from a genetically modified pig. The animal was grown commercially to provide meat to individuals with a meat allergy transmitted by a tick bite. The animal was manipulated to deactivate a gene that ordinarily would prompt immediate rejection of the organ from any human recipient of the kidney. A collection of thymus tissue was also transplanted from the pig to the human to further manipulate the immune system response to the foreign tissue. The thymus is a vital part of the pig and human immune systems and plays a role in the body’s reaction to foreign tissue. Additionally, drugs to suppress the human immune response that would customarily reject the foreign kidney were also administered.
‘Brain death’ is diagnosed on the basis of numerous failures in brain function that have been accepted as indications that recovery and even survival of ongoing heart, lung, and other organ systems are impossible. Patients exhibiting this loss of brain function usually experience a cardiac arrest within a few days. An uncelebrated accomplishment in the NYU/Langone pig kidney transplant was that the recipient of the organ had been kept alive for more than a month after he was deemed ‘brain dead.’
Obviously having a viable kidney was an important feature in maintaining the survival of the ‘brain dead’ recipient. The team at NYU/Langone had previously succeeded in kidney transplants from animals over the past two years, and in fact other medical centers, including the University of Alabama, had had similar success transplanting pig kidneys into ‘brain dead’ human recipients. Viability of the transplanted organ for more than a month was actually the only unprecedented accomplishment. The next obvious step is to attempt a transplant into an individual with no kidney function who is otherwise largely intact. The longterm goal is to develop organs and medications that will allow people who have gone into kidney failure to have normal kidney function with transplants from animals, rather than being dependent on renal dialysis for the rest of their lives. If this works, it will help pave the way for transplantations of other animal organs into people.
Although the team at NYU was understandably enthusiastic about their accomplishment, this advance in transplantation is actually a very small step. What is needed is a method that allows replacement of diseased human kidneys with healthy animal kidneys for decades, rather than days. We are still heavily dependent upon transplants from live donors and from people who have died to people who are likely to die or to become dependent on machines that restrict their activities for the rest of their lives. The drugs needed to suppress rejection of transplanted organs, including the kidneys, heart, lungs, liver etc., are generally quite toxic, but there are few alternatives to using these drugs. Efforts to produce artificial implantable organs, such as mechanical hearts, have been failing for many decades. That this team has demonstrated the feasibility of using an animal kidney to maintain normal kidney function in one man for one month is far from establishing the value of this type of transplant for maintaining kidney function in other humans for decades. It is nonetheless a step in the right direction.
The real and unmentioned advance in organ transplants was the development of the gene-altered pig. Not only were human genes transferred to the pig embryo but also a pig gene that would have triggered abrupt rejection of the transplant was shut off. The ability to “knockout” genes and to implant genes foreign to the developing animal holds much greater promise than any advances in surgical technique. Truth be told, the surgical techniques involved have been available for more than 50 years, and they could be performed by an experienced fourth year medical student. What was most important in the announcements from the transplant team was that the work done by genetic engineers had been successful and had allowed the transplant team to make progress in their continuing efforts to find a solution to the shortage of human kidneys for transplantation.
The news conference itself demonstrated several facets of modern medicine. This work was reported to the media prior to its being published in medical journals. The people representing the transplant team were strictly male, and there was no one involved who discussed the outlook or feasibility of further manipulating the donor animals to minimize or eliminate the need for drugs to suppress the immune system. The news conference was a celebration of a relatively small advance in the area of organ transplantation. The obvious purpose of the news conference was to portray NYU as a major player in the lucrative field of organ transplants.
These types of media events have become increasingly routine in recent years as medical centers compete with each other for patients and financial support. The hospital and doctors fees for the typical kidney transplant routinely exceed $400,000. This does not include the charges for screening and follow-up care. Any institution that can establish itself as a leader in the area of transplant medicine will attract patients from across the country. The financial rewards to the institutions [and the surgeons] performing transplants are already substantial. These rewards would be virtually limitless if the supply of replacement organs itself became limitless.
Dr. Lechtenberg is an Easton resident who graduated from Tufts University and Tufts Medical School in Massachusetts and subsequently trained at The Mount Sinai Hospital and Columbia-Presbyterian Medical Center in Manhattan. He worked as a neurologist at several New York Hospitals, including Kings County and The Long Island College Hospital, while maintaining a private practice, teaching at SUNY Downstate Medical School, and publishing 15 books on a variety of medical topics. He worked in drug development in the USA, as well as in England, Germany, and France.
