ブタの腎臓をヒトに一時移植、米で初成功

【ワシントンＡＦＰ＝時事】米ニューヨーク大学ランゴーン医療センターの外科医らが、ブタの腎臓をヒトに一時的に移植することに成功した。臓器移植における画期的な進歩で、手術を行った医師は「奇跡を起こす可能性を秘めている」と述べている。（写真は遺伝子操作されたブタの腎臓のヒトへの移植手術で、拒絶反応の兆候がないか確認するニューヨーク大学ランゴーン医療センターの医療チーム）
　先月２５日に行われた手術では、脳死状態で人工呼吸器を必要とする患者の脚の付け根の血管に、遺伝子操作で免疫系の拒絶反応を引き起こす遺伝子を取り除いたブタの腎臓をつないだ。患者の家族は、科学の進歩のために、２日間の実験を許可した。
　ランゴーン医療センター移植研究所のロバート・モンゴメリー所長は、移植したブタの腎臓が「想定した通りの役割を果たし、老廃物を取り除いて尿をつくった」とＡＦＰに語った。
　重要な点として、腎臓の機能レベルを示す指標であるクレアチニンの値が手術前は上昇していたが、ブタの腎臓を移植した後は低下したことが確認できた。
　モンゴメリー氏によると、この患者は臓器提供の意思を表明していたものの、どの臓器も移植に適していないことが判明し、家族は落胆していた。だが「今回の実験が別の形で臓器提供に寄与する機会だということに、家族は安心したようだ」という。５４時間に及ぶ実験の後、患者は人工呼吸器を外されて亡くなった。
　ブタの腎臓は、ヒト以外の霊長類に移植した場合、最長で１年間機能することがこれまでの研究で確認されているが、ヒトへの移植が試みられたのは今回が初めて。
　モンゴメリー氏は「３週間後、３か月後、３年後に何が起きるかは、まだ分からない」としつつ、「これは本当に重要な中間ステップで、少なくとも最初のうちはうまくいきそうだということが分かった」と説明。今後１～２年以内に臨床試験を実施できる可能性があると述べた。
　英バーミンガム大学のハイネック・マーゲンタル医師（外科）は、今回の実験結果が確認されれば「臓器移植分野における大きな前進となる。移植用臓器の深刻な不足を解消できるかもしれない」と期待を示した。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2021/10/22-14:34）

A US medical team has succeeded in temporarily attaching a pig's kidney to a person, a transplant breakthrough hailed as a potential miracle by the surgeon who led the procedure.
The surgery, carried out on September 25, involved a genetically modified donor animal and a brain dead patient on a ventilator whose family had given permission for the two-day experiment, for the sake of advancing science.
It did what it's supposed to do, which is remove waste and make urine, Robert Montgomery, director of the transplant institute at New York University (NYU) Langone, told AFP in an interview.
Critically, the organ was able to reduce the level of the molecule creatinine, a key indicator of kidney health that was elevated in the patient prior to the transplant.
Montgomery carried out the surgery with several colleagues over the course of around two hours.
They joined the kidney to blood vessels on the top of one of the patient's legs, so that they could observe it and take biopsy samples.
The patient had wanted to be an organ donor and their family was initially disappointed when told their loved one's organs were not suitable, said Montgomery.
But they felt a sense of relief that this was another opportunity for donation, he said. The patient was taken off the ventilator and passed away following the 54-hour test.
- 'Important intermediate step' -
Earlier research has shown that kidneys from pigs are viable in nonhuman primates for up to a year, but this was the first time it had been attempted with a human patient.
The donor pig belonged to a herd that had undergone a genetic editing procedure to knock out a gene that produces a particular sugar, which would otherwise have triggered a strong immune response and led to organ rejection.
The editing was performed by biotech firm Revivicor, a subsidiary of United Therapeutics.
It is still a question what would happen three weeks from now, three months, three years, said Montgomery.
The only way we're really going to be able to answer that is to move this into a living human trial. But I think this is a really important intermediate step, which tells us that at least initially, things are probably going to be okay.
He plans to submit the findings to a scientific journal in the next month, and says a clinical trial could take place in around a year or two.
The news was welcomed cautiously by outside experts, who nonetheless said they would like to see the peer-reviewed data before drawing firm conclusions.
This news is a significant scientific achievement in the xenotransplantation field, Hynek Mergental, a surgeon at the University of Birmingham in Britain said in a statement.
If confirmed, it would be a major step forward in the organ transplant field that might solve the critical shortage of donor organs, he added.
- Organ shortage -
The news comes amid a dire shortage of transplant organs.
According to official US data, there are nearly 107,000 Americans awaiting an organ -- 90,000 of whom need a kidney. Seventeen Americans die each day while waiting for an organ.
To meet demand, doctors have long been interested in so-called xenotransplantation, or cross-species organ donation, with experiments tracing back to the 17th century.
Early research focused on harvesting organs from primates -- for example a baboon heart was transplanted into a newborn known as Baby Fae in 1984, but she survived only 20 days.
Today, pig heart valves are widely used in humans, and pig skin is grafted on human burn victims.
Pigs make the ideal donors because of their size, their rapid growth and large litters, and the fact they are already raised as a food source, said Montgomery.
For Montgomery, the research has a personal dimension: he himself was on a waitlist for a heart transplant, which he finally received two years ago.
The technique could one day provide a renewable source of organs, much like wind and solar provide sustainable energy, he said.
I think people will see that and accept that, particularly the people who are waiting and desperate -- they will see this as a potential miracle for them as we move this forward.