Interview
Why pig organ transplants are closer than ever
- Current Organ Shortage Statistics:
- Approximately 90% of people globally in need of an organ transplant do not receive one (only 10% are successfully treated).
- Rationale for Xenotransplantation:
- Thirty years ago, the field coalesced around genetically modified pig organs as the primary solution to the shortage.
- Rejection of Non-Human Primates:
- Apes and primates are deemed unsuitable due to ethical concerns regarding their similarity to humans.
- There is a significantly elevated risk of pathogen spillover and infection transmission from primates to humans.
- Advantages of Pigs:
- Pigs provide organs with physiological size compatibility with humans.
- Pigs exhibit sufficient physiological similarity in blood clotting and urine production, despite minor differences requiring genetic editing.
- Pigs can be bred on a large, industrial scale, unlike primates which have low reproductive rates.
- Genetic Modification Process:
- Scientists cannot simply match blood types or select existing pigs; genetically edited pigs must be created from scratch.
- Step 1: Removal of Antigens:
- Specific sugars (carbohydrates) on pig cells that trigger strong human immune reactions are identified and switched off.
- Step 2: Addition of Human Genes:
- Human genes are inserted to produce signals that help the body accept the organ.
- Additional human genes are added to regulate physiological functions, such as blood clotting, to match human biology.
- Distinction from Existing Applications:
- Pig heart valves are currently used for structural functions and do not require this level of genetic and biochemical fine-tuning.
- Whole organ transplants require extensive genomic editing to prevent rejection and ensure compatibility.
- Logistics and Timeline:
- Edited piglets require a growth period of approximately six to eight months (average seven months) to reach human-organ size compatibility.
- This timeline aligns closely with the standard age at which pigs are slaughtered for food.
- Ethical and Environmental Considerations:
- Pigs for transplant are raised in sterile environments from birth to death, eliminating exposure to external pathogens or farm conditions.
- While the concept of growing animals for human consumption of organs may be perceived as "icky" by some, the urgency of the organ shortage generally secures public acceptance.
- Future Outlook:
- Adoption Criteria: It is anticipated that pig organs will initially be reserved for specific criteria patients rather than replacing human organs immediately.
- Superiority Potential: Tailor-made pig organs could eventually surpass human organs in quality, as human-donated organs vary in condition due to donor history and disease.
- Long-term Trajectory: Pig transplants may not be the final step in the field; future technologies for organ creation may emerge to further supersede current methods.