BIOPOLITICS: XENOTRANSPLANTATION

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THE WAY TO PROCEED WITH EXPLORING XENOTRANSPLANTATION


INTRODUCTION

The definition of Xenotransplantion

"Xenotransplantation" is a new word that it is not even found in many nonmedical dictionaries. When writing this word on computer for example, it will be redlined as a sign of an unrecognized word. It specifically refers to the transfer of body parts from a member of one species into a member of a different species. For the purposes of this discussion, however, the term xenotransplantation generally will refer to the replacement, typically by a surgical operation, of a damaged or diseased vital organ or part (such as a liver, heart valve, or tissue) by a healthy version of the same organ from an animal (such as a baboon or a pig) into a human being.
Following to the Food and Drug Administration (FDA) , xenotransplantation refers to any procedure that involves the transplantation, or infusion into a human recipient of either: (a) life cells, tissues organs from a nonhuman animal source, or (b) human body fluids, cells, tissues, or organs.
According to Department of Health and Human Services (DHHS), "xenotransplantation" refers to any procedure that involves the use of live cells, tissues, or organs from a nonhuman animal source that are injected, implanted, or transplanted into a human being. (These live nonhuman cells, tissues, or organs are called xenografts). Xenograft products include combination products that contain xenografts in combination with drugs or devices, and may be derived from transgenic or nontransgenic animals. (Transgenesis is the process of introducing a gene into an animal, usually for experimental purposes.) Although it would seem that many of the same ethical and economic issues would be implicated, the DHHS definition of xenograft products specifically excludes such significant nonliving animal products as porcine heart valves (regulated by FDA as medical devices), porcine insulin (regulated as a drug) and bovine serum albumin (regulated by FDA's Center for Biologics Evaluation and Research (CBER).

The distinction between organ and tissue xenotransplants

There is a clear difference between organs and tissues xenotransplantation. The break news seems to put more attention into organ xenograft rather than tissue xenograft. The extensive thoughts of organ xenograft because it involves blood transmission consequently deliver retrovirus to the recipient. Therefore, the public attention concerns more likely to the organ xenotransplants than tissue xenotransplants. Organ xenotransplants could include whole hearts, lungs, livers, kidneys or pancreas of animals. Tissue xenotransplants could include skin grafts for burn victims, corneal transplants for the visually impaired or bone transplants for limb reconstruction. The public concern has been more likely about the organ xenotransplants than tissue xenotransplants because the former delivers blood that is believed to contain retrovirus.
Even though it is not as an immense an issue as organ xenotransplant, tissue xenotransplants have shown potential benefit to human treatment’s disease. Cellular xenotransplants may be a way to treat people who have diabetes or Parkinson's disease. Ongoing “clinical trials” include the use of fetal porcine neural cells to treat intractable epilepsy (the only other therapy is a lobectomy), refractory Parkinson's disease, and Huntington's disease; various animal tissues as skin grafts for burn victims; baboon bone marrow to alleviate the effects of AIDS; bovine adrenal cells to relieve intractable chronic pain; encapsulated porcine islet cells to treat diabetes mellitus; xenogeneic hepatocyte cells as extracorporeal liver-assist devices; and porcine livers as a temporary bridge to human organ transplantation .
Being potential curing some diseases and bridging the gap of shortage organ, however, xenotransplantation exists with debatable issue between pros and cons. The pros argue that the potential benefit of xenograft can aid humans from the scarcity of organs. The cons maintain xenograft transfers the retrovirus risk and this is an ethical issue. On the other hand, the policy of proceeding with xenotransplantation is obviously the window to continue any possibilities of processes developed for xenotransplantation. Understanding the demand for more organs, the possibility of animal organs and the caution of current policy preventing the risk tempt the author to examine the policy to continue xenotransplantation. The paper question : how effective is the current policy in paving the way to proceed with exploring xenotransplantation? Especially when the scientists find the challenges with xenograft, they must also define how to obtain a means of risk assessment, risk prevention and risk management.



XENOTRANSPLANTATION DIMENSSION

The demand for more organs

Transplantation is now well known as a solution to cure patients with end-stage organ failure when medication with drug or restorative surgery is not viable. Consequently, the successful progress in organ transplants is an increasing demand for therapy and as a result, for additional human organs. Currently, this demand cannot sufficiently be met because of a donor scarcity . A lack of human organ donors has created the need to find an alternative. According to Caplan , a number of research groups explore the option of using animals as the source of transplantable organ issues.
The demand for human organs in the United States alone increased by 49 percent between 1988 and 1997, from 12,786 to 20,672, and the length of the waiting list also increased. In 1997, the number of transplant recipients represented less than half the patients on the waiting list. Similar to the USA, Western Europe has 40 000 patients are waiting for kidneys, while the number of donors has remained stable at around 5000 for the past few years.
The inequality in supply and demand has made this situation poorer by two factors. One is a decrease in the number of accidental deaths—and, thus, in the number of possible donors –resulting from, for example, mandatory use of seat belts in automobiles and crash helmets when riding a motorcycle, together with laws outlawing drinking and driving and lowering speed limits. The other factor is the relative failure of health education programs, which has led to an increase in the number of potential transplant recipients; for example smoking, alcoholism, and consumption of animal fats, together with population that steadily growing older and is thus more disease-prone. Have increased the number of individuals in need of heart or liver transplant. Because of these factors, a significant percentage of people on organ transplant waiting lists die before a donor becomes available (see table 1).
Table 1. Numbers of patients on the U.S. Waiting Lists in 1999 (a) and Receiving Organ Transplants in 1997 (b)

Organ Number of Patients on U.S. Waiting Lists as of June 2,1999 Number of the U.S.Transplants Performed During 1997 Where Organ Was obtained from a Brain-Dead Donor Number of the U.S.Transplants Performed During 1997 Where Organ (or Part of Organ) Was obtained from a Living Donor Total Number of the U.S. Transplants Performed During 1997
Kidney
Liver
Pancreas (or Pancreas + Kidney)

Heart
Lung
Heart + Lungs
Intestine
Total 42,071
13,095

2,317

4,277
3,299
238
119
63,635 7,759
4,100

1,055

2,292

911

62

65

16,244 3,669
68

6


0

17

0

2

3,762
11,428
4,168


1,061


2,292

928

62

67

20,006
Source: United Network for Organ Sharing (UNOS)
a) Data as of June 2,1999
b) Data from UNOS Annual Report, 1998

Every attempt has been made both to promote organ donation and to utilize those organs that becomes available. In the United States, the United Network for Organ Sharing (UNOS) synchronize organ donation throughout the country, and similar networks are present throughout Europe and elsewhere. In Europe, for example, lawmakers have introduced “presumed consent” law, whereby a potential donor can be considered to have consented to donation unless he registered an objection during his lifetime; however, a few transplant centers will take away organs from a potential donor in the face of family disagreement, even though this would be permissible in such countries, and yet donor supply more and more will be unable to meet demand. To bridge the gap between organ supply and demand, it was agreed that xenotransplantation was the only real hope.

The prospect and case of xenotransplantation
Xenotransplantation – the transplantation of viable organs from one animal species to another was first practiced in the early 20 century, with kidney xenografts from rabbits, pigs, goats, lambs and nonhuman primate donors (e.g. macaques, chimpanzees, marmosets, baboons). The earliest attempt at transplantation of an animal kidney was probably in 1902 by Emerich Ullman in Vienna, who transplanted a pig kidney into a blood vessel in the arm of a woman . The transplantation of an animal heart happened in 1964 from a chimpanzee heart transplant by James Hardy. In 1997, Barnard used chimpanzee and baboon hearts to prolong the survival of patients who had just undergone unsuccessful transplants for four days, after the first transplanted heart was rejected.
On October 26, 1984, in California, most people first became aware of xenotransplantation. Dr. Leonard Bailey of the Loma Linda University Medical Center transplanted the living heart of a seven-month-old female baboon into the chest cavity of a newborn human infant whom the press dubbed "Baby Fae." Baby Fae suffered from a congenital birth defect known as hypoplastic left heart syndrome and would have died immediately without a transplant; with a transplant, she survived twenty days. The last attempt of xenograft in Poland 1992, and a man survived for almost 24 hours after he had a pig heart transplanted and in India 1996.
Experimental xenotransplantation was not attempted seriously until the 1960s, and the twenty American xenotransplantation recipients rarely have survived such operations for even a month. A number of possible organ xenograft has been applied to human shows in Table 2, that was recorded since 1906. The first recorded was pig’ kidney which was only survived for three days in human body in 1906. The shortest survival time was less than 24 hours from baboon’s heart transplanted in 1968 and in 1992 baboon’s liver. The longest survival time was chimpanzee’s heart for nine months stay in human body in 1963. Among twenty-one organ transplantations, kidney was the most frequently to be transplanted. Examining the year of transplantation and the amount of time survival, however, showing is no significant line that the recent experiment will result the longer survival time of recipient.
However, political and scientific sensibilities today clearly differ from those of the 1960s, and so the critical assessment of xenotransplantation must be more rigorous than the previous discussion. The socio-legal and ethical issues beg not to continue proceeding with xenotransplantation. For instance, it should be banned for both reasons: the ethical issues and the safety risk over possible transfer of animal viruses into human.
Table 2. Animal organs transplanted into human, 1906 – 1995
Donors Organ Transplants Survival time Author Year
Pig
Goat
Macaque
Sheep
Baboon
Macaque
Chimpanzee
Baboon
Chimpanzee
Chimpanzee
Chimpanzee
Baboon
Chimpanzee
Chimpanzee
Pig
Baboon
Baboon
Pig
Baboon
Baboon
Baboon
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Kidney
Heart
Heart
Heart
Heart
Liver
Liver
Bone marrow 1
1
1
1
1
1
3
6
1
1
6
6
31
2
1
1
1
1
1
1
1 3 days
3 days
32 hours
9 days
4 days
12 days
9 months
60 days
-
1 day
one 9 mths
max 60 days
49 days
4 months
31 days
0 day
-
20 days
< 1 day
70 days
26 days
- Jaboulay
Jaboulay
Unger
Neuhof
Hitchcock
Reemtsma
Reemtsma
Starzl
Hardy
Hume
Reemtsma
Starzl
Traeger
Goldsmith
Cortesini
-
Barnard
Bailey
Starzl
Starzl
Gorman 1906
1906
1910
1923
1963
1963
1963
1963
1964
1964
1964
1964
1964
1965
1966
1968
1977
1985
1992
1993
1993
1995
Source : Mohaci, Thomson and Quine (21) in A.S. Daar “Animal-to –human organ transplants a solution or a new problem?”, The International Journal of Public Health, no.1 1999


FDA, one time, did not approve any primate xenograft, but is encouraging further research on primates to study virus transmission to humans. Other counter arguments claimed that there are safer and more humane alternatives to xenotransplantation that are not being explored by regulatory authorities. These include aggressively promoting preventive medicine and increasing human organ donation rates as many European countries have successfully done through various legislative schemes.
Possibly benefit of xenotransplantation
Despite the technical barriers and potential risks, and the unsuccessful recipient survival record so far, xenotransplantation is acknowledged to show significant promise today both as a treatment for a wide range of diseases, including chronic metabolic and neurological disorders, and as an alternative source of cells, tissues, and organs for clinical transplantation. The potential benefit for successful xenotransplantation proceeded is viable treatment to all patients who are currently waiting for organs. Up to now, the benefit of using animal tissues has cured some diseases. The high expectation is that Xenografted whole organs will reduce costly organ waiting times and return patients more quickly to productive health.
Moreover, once the technical problems with xenotransplantation have been overcome, there are several reasons why one could argue that xenotransplantation is preferable to allotransplantation . Firstly, source animals and their organs can be specifically prepared transgenically; their deaths can be planned, coordinated with the needs of the recipient and the transplant team, and scheduled appropriately just prior to the operation; none of these conditions would be considered ethical by anyone were human organ donors involved. Secondly, certain animals have proven to be resistant to some human diseases. For example, baboons and their livers are resistant to hepatitis B, so there is no reason to believe that a transplanted baboon liver would contract that disease, whereas a transplanted human organ could be destroyed by the very same virus that may have destroyed the original organ, thus rendering the entire procedure nugatory.
For these reasons, academic and commercial sponsors are pursuing actively the development of xenograft products and their clinical application. Drug and biotechnology companies already have poured well over $ 100,000,000 into xenotransplant research. Recent improvements in immunosuppressants and surgical techniques work toward a future certainty that xenotransplantation will be successful in the long term. It is therefore, an appropriate time to thoroughly explore the extra-clinical aspects of xenotransplantation, and particularly the ethics of xenotransplantation.


POLICY ON XENOTRANSPLANTATION
The caution of current policy preventing the risk
It is not different to any new medical technology, xenotransplantation comes with massive promise and some unknowns. The main discussion of xenotransplantation however has changed from concern about rights and welfare of potential non-human source animals to concern about the risk of xenozoonoses. The risk of transferring microorganism from an animal to a patient is a major distress when performing pig-to-human transplants, for instance. In a standard risk assessment scheme, two main factors need to be addressed: firstly, the possibility of contagious incident and viral contamination; Fishman makes distinctions with transplants using different cells or tissues, “...different stains of donor animals, different genetic or immunological manipulations of the donor or different immunological conditioning regimes (for host and donor) are not equivalent in terms of infectious risk and must be evaluated individually… “ (Fishman,NYAS `98). Secondly, the judgment of transferable virus may spread to the general public.
The fear of Xenotransplantation is clear about zoonotic infection. The risk identified was zoonotic contagion resulting from a virus or other pathogen that crosses the species barrier and infects the human host. The remote chance of an infection that causes disease only in the new host would not necessarily create any ethical concern, since the recipient was deriving benefit from the transplant. The ethical issue is mainly the possibility that the zoonotic disease could be spread to other humans who did not receive the same benefit as the recipient. This is what Fishman said previously that the general public could be put into risk.
In the United States, the Public Health Service (PHS) of the Department of Health and Human Services (DHHS) drew up draft guidelines in 1996 that likely will have to be followed by most planning to use animal cells or organs. Most of the regulations in xenotransplantation relate to the risk of transmitting infectious diseases . In response to the caution of the risk, some scientists, including a number of virologists, pointed out the real danger of infection from non-human primates.
Essentially, some effort has been used to minimize the infectious risk by federal government as well as health companies, yet the worries remain as mainly rejection from immune activation of recipient after transplantation. To some extent, when an organ is transplanted, no matter how closely it is matched, rejection at some level will occur. This is because the body's immune system is extremely effective at recognizing foreign surface proteins, which will be present in the tissue from the donor. The only exception occurs in donations from one identical twin to another.
Furthermore, to promote the success of the transplant, the recipient ingests drugs to suppress the immune system, which also makes the recipient more susceptible to ordinary diseases. Therefore, the strength of “immunosuppressive drugs” must be increased to accommodate the body's more virulent rejection. The other is infectious cell migration from graft to the host; or the genetic recombination such mutation that can disguise the infection. Therefore, medical research interest has centered on overcoming the body's natural immune system mechanisms that lead to organ rejection.
To minimize the potential transferable virus, the US Food and Drug Administration (FDA) has proposed new rules that would require researchers doing human trials of “gene therapies” and providing safety information about the treatment such as untoward effects seen in animal studies, and the side-effects and adverse reactions that occur once a trial begins. In considering public health policy, the gene therapy can be utilized.
However, the FDA acted to restore public confidence in gene therapy and
xenotransplantation research after a series of scandals involving gene therapy
in human beings broke last year. The revelations began after Jesse Gelsinger, an
Arizona teenager who had volunteered to participate in a gene-therapy trial,
died of a side-effect that critics charge should have been anticipated given
findings from animal studies and side-effects that had been seen in other
volunteers (see Lancet 2000; 355: 384). Gelsinger‘s death prompted a national
review of gene-therapy trials in the USA, which found that many trials seem to
have been sloppily done. The findings led to the closure of some trials and the
suspension of others.
Another concern for caution of xenotransplantation is the industry involvement. It has been spot news where industry invests resources and biotechnology companies’ work together with academic centers. The market study by Peter Laing (1996) reported a significant potential for profit, which attracts private investment. The market estimation is 100 000 patients a year.

Scientist views on xenotransplantation


In June 1996, doctors and professors met to study about public policy in xenotransplantation, organized by The Institute of Medicine (IOM). The are five recommendation for human trial that state for caution of proceeding xenografty :
First, to screen animal from the existence of infectious virus; sustained observation throughout patients’ lifelong and regular examination of their contact—families, health care workers, others, for the indication of transferable disease; the system of tissue banks enable to collect the to tissue samples and blood from source animals and patients; and the national and local system to register patients who are receiving xenotransplants. Such effort should be systematized with international registries and databases.
Second, the board required all the scientists and the association to carry out xenotransplantation trials in humans. They are recommended for sustained observation of infectious risk and follow the national instructions. Xenotransplant patients are monitored throughout their lifetimes and physicians periodically monitor persons with whom they come into contact (families, health care workers) for evidence of infectious disease.
Third, the board mentions additional research into the special ethical issues that are elevated by xenotransplantation, mainly those linked to “informed consent” as the condition for lifetime observation of patients and those connected to equality and fairness in distributing organs, besides study about the psychological and social effect of getting animal organs on recipients, their families, and members of the society as a whole.
Fourth, the board requires the instrument within the Department of Health and Human Services to guarantee necessary harmonization of the federal agencies and other component concerned in enhancement, failure, and assessment of established procedure.
Fifth, the board requires that if the science stand for particular types of xenotransplants is considered adequate and the accurate protections are prepared, well-chosen human xenotransplantation trials using animal cells, tissues, and organs would be justified and should proceed.
From the regulatory point of view in the United States, the freewheeling days when any surgeon could transplant an organ from an animal with the permission only of the Local Institutional Review Board were over. All such experiments now required a specific Initial Notification of Drug application to the US Food and Drugs Administration (FDA) . The field was new, and so the FDA set up a panel to review the applications. Arguments in favor of proceeding were that this was a valid experiment, that the scientific justification was adequate, and that if the experiment were not done in the United States it would be done elsewhere, and the United States would lose out.

The International Concern on Xenotransplantation
Having a vigorous impact on human life, the Organization for Economic Co-operation and Development (OECD) and The New York Academy of Sciences (NYAS) sponsored the International Workshop on Xenotransplantation which brought together researchers, clinicians, regulators, ethicists, advocates, legal experts, and economists to achieve a common understanding of the benefits and risks associated with xenotransplantation.
A number of professors in the meeting uttered about the benefit from of non-human primates, especially baboons and monkeys, as organ donors, as well as the fact that the recipient would be heavily immunosuppressed. Public should have known that xenotransplantation contains the combination in its risk and benefit. Meaning, xenotransplantation reflects a whole spectrum of activity, ranging from pig islets without immunosuppression at the safest end of the spectrum, to baboon heart transplants with immunosuppression at the riskiest end of the spectrum. The difference between those two extremes of xenotransplantation is greater than the difference between xenotransplantation and allotransplantation. To regulate and practice these extremes as if they shared the same risk/benefit profile would waste an inimitable opportunity to safely deliver provable benefit from xenografts in the near term.
Therefore, the scientists pictured the risk profile that explicitly demonstrates the different of tissue and organ xenograft. Table 3 shows the obvious comparison of both. The scientist purposes’ are to make sure the guidelines and policy will meet with the reality. Diabetes has been identified as a safest end of xenotransplantation, while kidney failure diagnosed as midrange of xenograft, however heart failure positioned as the riskiest end of xenograft spectrum. Islet xenografts were the logical first choice for proceeding with xenotransplantation. Since islets are free tissue not connected directly to the recipient’s vascular system. Although whole organ xenografts will provide tremendous life-saving potential, they represent a greater challenge and more unknowns that islet xenografts. By demonstrating success and safety in the least challenging end of the xenotransplantation spectrum, both governments and the public will be more friendly to the promise of whole organ xenografts.
The World Health Organization (WHO) has developed a global framework for emerging infectious diseases. Three of the systems are obligated to observe infectious diseases: global monitoring and alert, global control, global information access, and national surveillance and control. The goal of these network system is to prevent the spread of the potential risk, the virus transmitted from one place to another place.

Table 3. Comparison of Potential Xenograft
Safest End of
Xenotransplantation
Spectrum Midrange of
Xenotransplantation
Spectrum Riskiest End of
Xenotransplantation
Spectrum
Disease Treated Diabetes Kidney Failure Heart Failure
Organ Transplanted Pancreatic Islets Kidney Heart
Donor Animal SPF pig SPF transgenic pig Baboon
Immunosuppression None (Immunobarriers) Systemic (Lifelong) Systemic (Lifelong)
Graft Failure Return to insulin injections Dialysis Death
Source : Robert E. Michler, Director of Heart Transplant ServiceDivision of Cardiothoracic Surgery Columbia-Presbyterian MedicalCenter, New York, NY, USA, the topic was discussed in OECD meeting.

Global monitoring and alert have a certain international unity awareness. The objective of this system is to strengthen WHO information networks on infectious and zoonotic diseases as to ensure early detection of global threats to public health. The following are among the currently available disease networks: arboviruses and haemorrhagic( headed by Rockefeller Foundation); the WHO influenza network(laboratory in the Netherlands); the WHO neuroscience networks.
The global monitoring and alert networks also report antimicrobial resistance events. In this area, the gonococcal antimicrobial sensitivity programme is most advanced and links 45 national laboratories and WHO Collaborating Centers, which provide training and external quality assurance. Notification of infectious disease is regulated by the WHO International Health Regulations (IHR), which was first drafted in 1969. In 1981, they were modified to mandate the reporting of three diseases: plague, yellow fever and cholera. The regulations also set out standards and norms to prevent the spread of infectious diseases at port of entry. The WHO-IHR are currently being revised to provide broader coverage of infectious diseases and to improve global reporting.
Global information access tends to provide international lively information about the transmission of disease. Furthermore, the WHO has built-up a pilot Website on disease epidemic, which is nourished by the confirmation system by official country reports and by non-governmental organizations. The site is to provide more information and larger geographic coverage ble, fast surveillance in each WHO member country. Positively, through its regional and country offices, the WHO has managed an advanced programme on national observation and control which enable WHO to confirm priority disease observation, anticipation and monitor.

EVALUATION OF POLICY

Simply says the conclusion of these debatable issues of continue or stop proceeding xenotransplantation is that there seems to be little enthusiasm for a blanket ban on xenotransplantation procedures. The current policy is effectual recommendations in paving the way to proceed with exploring xenotransplantation The recommendations are signed to the caution purpose, in order the further research and experiment of xenograft be obligated and be alert to any potential risk implication both to the recipient and to the public.
Plenty scientific indication designates that the risks of xenotransplantation are real and unquestionable respectively; there is also a real shortage of human organs available for transplantation. Herein lies the dilemma. Each year, real people, not just statistical figures on table as waiting list recipients, die because of an inability to find a compatible organ; the pleas by these people and their families are well documented and difficult to ignore. The option is xenotransplantation that scientists still struggled to combat the risk. For this reason, if for no other, it seems likely that xenotransplantation trials will eventually begin.
The existing policy shows the conscious regulation to proceed with xenotransplantation. Regarding the potential risk and benefit, however, the policy has lifted to proceed towards xenotransplantation. For example, the draft Public Health Service guideline was prepared to help minimize public health risks associated with xenotransplantation while not restricting access to promising therapies for individuals with life-threatening and chronic debilitating illnesses. The guideline applies to all types of xenotransplants, including cells, tissues and solid organs.
The policy also encourages for further research. Meanwhile, the whole organ xenograft have been able have been able to support human life for an extended period. It is this fact that investigators wish to exploit in clinical bridging studies. By providing temporary heart, kidney, or liver support as a bridge-to-transplantation, these biological devices may allow patients to recover end organ function and await allograft transplantation in a more stable clinical state, thus improving their chances of survival.
The International concern put consideration on the network information to proceed with xenograft. In the International meeting held by OECD, the scientists agree that clinical trials of xenotransplantation will be allowed to proceed in most countries under guidelines that assure adequate record keeping, reporting of adverse events, archiving of donor and recipient biologic samples, safe and humane animal management, long-term monitoring of recipients, and other procedures intended to reduce or eliminate risks. A moratorium with xenograft seems also be elevated in most countries of the world.
Within and outside of the United States generally recognized that the benefits of xenotransplantation are enormous, and the risks manageable. In the United States, the Food and Drug Administration stated very clearly that it would not impose a moratorium, as such a move is unnecessary and would only drive people seeking treatment to countries where the practice was not banned.

V. Conclusion

The success of Allotransplantation, the grafting of organs from human donors, has been a source of dilemmatic problem. The transplanting of organs such as kidneys, hearts, livers, lungs, pancreases, and lungs has saved so many lives that the demand for human organs is outstripping the supply by an accelerating margin. The organ donation systems have been implemented in some countries to cope with the demand for more organ. Nonetheless, more people are dying each year while waiting for a suitable organ donor.
Xenotransplantation is the one of possible and real way out to bridge the gap between organ supply and demand. Scientists have made a great effort to reduce the retrovirus risk. Debatable issues however have led to the policy that allowed xenotransplantaion to proceed. Under certain guideline, either the USA or international community (represent by WHO) considers the benefit over the risk of xenograft that convinces them to endorse the policy as wisely as alarm action to the human lives.
In sum, the way to proceed with exploring xenotransplantation is not stagnant or go-slow. In contrast, the policy to proceed with xenograft is moving fast as much thought of controlling the risk of transmitted virus from donors to recipients. At least, for now, xenograft has been able to be a bridge organ need until the recipients get the allotransplantation.