B. 基本倫理原則
人格（自律）の尊重（Autonomy）
恩恵（Beneficence）
正義（Justice）
生命倫理学４原則
自律の尊重 Respect for Autonomy 無危害 Nonmaleficence
善行 Beneficence
正義 Justice
哲学
倫理学
応用倫理学 生命倫理学
医療倫理学 研究倫理学
生命倫理学
医療倫理学 研究倫理学
尊厳死 脳死 妊娠中絶
遺伝子疾患 生殖補助医療
利益相反 研究不正
患者データ
ヒト由来試料 知財
人工知能
ケーススタディー1
X大学医学部附属病院に脳腫瘍のため入院する患者A は、認知症のため判断能力が低下している。認知症に
かかるより前、患者Aは、脳腫瘍に対する治療法Pにつ いて、希望しない旨の署名をしている。複数の医師は 現時点で治療法Pが最も有効な治療法であると確信し
ており、患者Aの家族もそれを望んでいる。
医師は患者Aの意思に反して治療すべきか。
ケーススタディー2
Y大学医学部附属病院に入院する急性骨髄性白血病 患者Bは、少しでも自分にとって有益である可能性のあ
る治療法について、リスクを問わず試したいと思ってい る。あるとき、患者Bの担当医はZ社が当該疾患を対象 とする新規化合物の治験参加者募集の情報を得た。こ
の担当医はZ社の株式を保有している。
この医師は患者Bに治験への参加を薦めるべきか。
最近のホットトピック
http://mag501.com/tragic-story-of-japanese-american-internment-during-ww2/
キメラ
http://dq3.sblo.jp/tag/%83L%83%81%83%89
http://dq3.sblo.jp/tag/%83L%83%81%83%89
より多くの臓器が必要
Source: U.S. organdonor.com (Department of Health & Human Services)
ヒト臓器工場としてキメラを使う
N E W S | I N D E P T H
2 6 2 16 OCTOBER 2015 • VOL 350 ISSUE 6258 sciencemag.org S C I E N C E
CREDITS: DIAGRAM ADAPTED FROM H. NAKAUCHI BY G. GRULLÓN; A. CUADRA/SCIENCE; PHOTO NAKAUCHI ET AL./THE UNIVERSITY OF TOKYO
bryos, could develop into brain cells, sperm, or egg cells in the chimeric offspring.
The U.S. National Research Council and the Institute of Medicine recommended lim-its on such research in 2005, among them that no human stem cells be added to primate embryos and that animhuman chimeras not be al-lowed to breed (Science, 29 April 2005, p. 611). Current NIH funding guidelines, finalized in 2009, reflect those recommen-dations. They prohibit breeding animals in which human stem cells might have become sperm or eggs, and they rule out pri-mate-human experiments. They do not, however, prohibit inject-ing human pluripotent cells into the embryos of other animals and letting the chimeras develop.
That is what several groups of
researchers are now trying to do. Their goal is to learn how to coax stem cells to become specific tissues or organs. Doing that in the lab, by recreating the 3D environment of a developing organ and reproducing all the signals it receives, is very difficult. “We don’t know how to guide the cells to become the cells we want,” Izpisúa Belmonte says. In-stead, he and his colleagues want “to use the animals as an incubator. We don’t know how they do it, but every day [developing ani-mals] produce perfect organs.”
So, Izpisúa Belmonte and others have set out to knock out the genes that drive the creation of specific organs or tissues, such as the pancreas, in an animal embryo and then inject human pluripotent stem cells into it. They hope that the human cells will preferentially fill the void left by the animal’s missing pancreatic cells, forming a human pancreas in the developing animal.
Earlier this year he and his colleagues identified a new type of human
pluripotent stem cell that seems to be especially good at contribut-ing to animal embryos. By inject-ing these cells into pig embryos, they have now made chimeras that have developed for 2 to 3 weeks. (He uses non-NIH funds for the work.) So far, Izpisúa Bel-monte says, no human cells have been seen in the nervous system.
The cells do, however, contrib-ute to the developing pancreas and heart.
The Pioneer Award would have enabled him to take the effort further, but last month Izpisúa
Belmonte received a letter from NIH saying that the application had been put on hold and inviting him to the upcoming meet-ing on chimeras. Izpisúa Belmonte will be there. “I applaud this workshop. It’s impor-tant to have guidelines so that researchers have a clear path in this promising and fast-moving area.”
An NIH spokesperson tells Science that the agency wants to “evaluate the state of the science in this area, the ethical issues that should be considered, and the relevant animal welfare concerns.” NIH says that no current grant has been halted by the fund-ing pause, but other scientists fear that the workshop is a step toward broader restric-tions, says Steve Goldman, a neuroscientist at the University of Rochester in New York whose work involves injecting human stem cells into mouse brains. That approach is not affected by the new rule, since he doesn’t work with early embryos, but NIH
has asked him to speak at the November meeting.
Sean Wu, who studies heart stem cells at Stanford University in Palo Alto, California, says the NIH notice prompted Stanford to urge scientists to be sure their experiments didn’t violate the new rules. “We were bombarded”
with emailed warnings, says Wu, who received an NIH New In-novator Award in 2008 to study interspecies chimeras. The uni-versity announcement came “out of the blue”, he notes, and has spread confusion and concern.
An NIH decision not to fund the work would be a big blow to the field, Wu says. “No one wants to do it if NIH won’t fund it.”
For Hiromitsu Nakauchi, a stem cell scientist at Stanford University, and the University of Tokyo, the debate is famil-iar. He showed in 2010 that by adding rat stem cells to mice embryos lacking a pancreas gene, he could grow a rat pancreas in a mouse. The technique also enabled his team to grow a pancreas from one pig species in the body of another. But the follow-up experiments he wanted to do with human stem cells in goat or pig em-bryos were forbidden in Japan (Science, 28 June 2013, p. 1509). An ethics commission decided that the experiments should be al-lowed, but official regulations still aren’t in place, Nakauchi says. In part because of the restrictions in Japan, he accepted a position at Stanford University, where he received $6.2 million for the work from the California Institute for Regenerative Medi-cine (CIRM).
Nakauchi’s project is proceeding with colleagues at the University of California, Davis, and at Stanford, where they have injected human induced pluripotent stem cells into sheep embryos. He was
plan-ning to apply for NIH funding to continue the work, and the agency’s announcement sur-prised him.
Using chimeras to grow human tissues is a long way from the clinic, Izpisúa Belmonte stresses, but his initial results have him optimistic that the approach is a viable one. “I am very excited about this project,” he says. “We need to do the experiments and see.” Whether NIH will support that work may be determined next month. ■
With reporting by Jocelyn Kaiser.
Human stem cells
Injection of human stem cells into pig embryos that are genetically modified to
lack specific organs Organ
transplantation
Generation of a human organ in livestock animals
Human organ