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Introduction

Why Xenotransplantation?

Xenotransplantation carries new hope as it may alleviate the shortage of human organs for transplantation.

Clinical organ transplantation is saving lives of patients with terminal organ failure and requires currently participation of other deceased or living donors individuals. The increasing number of patients with various organ failures and the inadequate supply of organs, has created a gap between organ supply and organ demand. This imbalance has resulted in increasing waiting times and number of deaths of patients on waiting lists. Xenotransplantation carries new hope as it may alleviate the current gap in human tissues for transplantation to meet all patients’ needs. Recent progress in the field of xenotransplantation has brought this method closer to clinical application and new clinical trials could be initiated soon.

What is Xenotransplantation?

Xenotransplantation refers to procedures in which live cells, tissues, or organs derived a non-human animal are transplanted, implanted, or infused into human patient. The categories of xenotransplantation procedures include the following: i) Solid-organ xenotransplantation is a procedure in which a source animal organ such as kidney or liver is transplanted into a human; ii) cellular and tissuexenotransplantation is the transplantation of tissues and cells from a source animal without surgical connection of any animal blood vessels to the recipient’s vessels; iii) extracorporeal perfusion occurs when human blood is circulated outside of the human body through an animal organ, such as a liver or a kidney, or through a bioartificial organ produced by culturing animal cells on an artificial matrix; iv) cellular and tissue xenotransplantation exposure to living animal-derived material is a procedure in which human body fluids, cells, tissues or organs are removed from the body, come into contact with animal cells, tissues, or organs and are then placed back into a human.
Xenotransplants have been performed in clinical trials or as unconventional therapies for a variety of conditions, or as cosmetic treatments.

What is the animal source?

Recent research in xenotransplantation has focused largely on the pig as potential source animal instead of non-human primates for a number of reasons. In particular, excellent breeding characteristics of pigs allow to generate large numbers of animals in closed colonies and to develop transgenic and cloned animals. Then, similar size of pig and human organs and similar physiology of the two species make the pig particularly suitable as a potential xenograft source. 

Hopes and Concerns?

Although xenotransplantation may open the door to a field with the potential to save thousands of human lives each year, it also carries the potential for transmission of infectious disease, both known and as yet unknown, from animals to human recipients and their close contacts. Dissemination beyond the original recipient into the general population could lead to epidemics. Potential public health risks posed by the use of xenotransplantation products include:i) transmission of organisms that are pathogenic for humans but may not be pathogenic or even detectable in the source animal host;ii) transmission of organisms that may not normally be pathogenic in humans but can become in the immunosuppressed or immunocompromised individual;iii) recombination or reassortment of infectious agents, to form new pathogenic entities.

Currently, porcine endogenous retroviruses (PERVs) have been of special concern because of their ability to infect human cells in vitro and because, at present, they cannot be removed from the source animal’s genome. To date, retrospective studies of humans exposed to live porcine cells/tissues have not found evidence of infection with PERV but more extensive research is needed. The risk from porcine xenografts or other zoonoses can be minimized with a strict regulation through good animal husbandry practices, construction of barrier-contained breeding facilities, appropriate controls for surgical procedures to harvest organs and screening of source animals for known infections. Close monitoring of recipients and archiving of specimens from them are important measures for minimization of infectious risk. These practices should be overseen by national health authorities in order to be effective in minimizing risk should an infection develop.

Xenotransplantation practices are currently performed in several countries with or without national oversight and regulation. It is important to collect data from all countries on all types of human xenotransplants in order to provide information for international agencies, national health authorities, health care workers and the public with the objective to encourage good practices, international guidelines and regulation and foster a better perception of hopes and risks in xenotransplantation.
That’s why we encourage national health authorities, health care staffs, research groups and the public to list human xenotransplantation practices taking place in their country. 

Why an inventory ?

The aim of this website is the establishment of an international human xenotransplantation database that will collect basic data on all types of xenotransplantation practices and to identify countries where such practices exist.
The inventory will not be detailed, but we hope it will help to determine  the current scope of human xenotransplantation practices in the world. Collected information will be reviewed by a panel of experts before being included in the database.

Which organizations are working for this inventory?

The International Xenotransplantation Association (IXA), a scientific and professional association of researchers in the field of xenotransplantation, and the University Hospital of Geneva, through theSurgical Research Unit, have established this database in collaboration with the World Health Organization (WHO) .  

What types of information?

The minimal information requested for the database would include the following:
  • Country and institution?
  • What is the therapeutic purpose of this human treatment?
  • Is the treatment part of a clinical trial?
  • What is the animal source for the xenotransplantation product?
  • What type of cells/tissues/organs was transplanted?
  • What is the source of information?
  • Have results been presented at a scientific Congress?
  • Have results been published in a scientific journal?
The information may be collected from various sources such as Internet, reports by members of the International Xenotransplantation Association (IXA), healthcare providers, research groups or any other public or private interested partners.
You will find an electronic questionnaire available on this website (Questionnaire). We invite you to fill this questionnaire and to send it to our office located at the University Hospital of Geneva, for review (Contacts). After verification by a scientific committee, the information will be put on the website (Database). This site will be updated on a regular basis. 

Conclusion

Finally this” Inventory of human xenotransplantation practices” is not for informational purposes only and will include only basic information without criticism or judgement. It will be available to national and international health authorities, health care workers and the public.