我们或许永远等不到“换头术”成真的一天

不久前的一则新闻让整个互联网沸腾了——意大利神经外科医生塞尔吉奥•卡纳韦罗和中国哈尔滨医科大学的任晓平医生实施了世界首例成功的人类头部移植手术（不过此次手术是在尸体上进行的，让人不免联想到弗兰肯斯坦和他的怪物）。卡纳韦罗称，此次手术是成功的，它标志着完整的甚至是活体的头部移植术可能“即将来临了”，将来，由于种种疾病导致身体彻底损坏的病人或许将能等来一具新的身体。

不过近几年来，卡纳韦罗和任晓平的研究也为他们招来了不少怀疑声浪，有不少学者既质疑换头术在科学上是否可行，同时又对它的伦理影响提出担忧。一些知名医生甚至公然否定了“换头术”的可行性。不过在各种批评声中，据称卡纳韦罗和任晓平已经相继在老鼠甚至猴子身上成功进行了头部移植手术。

可以想见，要成功实施“换头术”，必然会面临很多重大阻碍。且不说要对头部和颈部组织、神经细胞和脊髓进行桥接，确保新的身体“能用”，患者能不能挺过这样一次耗时极长的手术也是个大问题，就算坚持下来了，脑袋和新身体会不会产生严重的排异反应也是个未知数。

拿目前极具开拓性且已经经过临床验证的生物工程为例——比如用基因技术操纵血癌患者的免疫细胞，将其变成抗癌细胞，然后重新注入患者体内。就是这种貌似理论上无懈可击的技术，也会导致严重的毒副作用。而一个新的头部和大脑会给身体带来什么样的长期影响，或者反过来，一具新身体会给头部和大脑带来什么样的长期影响，也依然是未知数，结果是高度难以预测的。

神经科学家迪恩•伯内特就在一篇专栏文章里指出，卡纳韦罗声称的一些以往的成功案例，其实与现实情况并不完全相符。比如那只实施了换头术的猴子并没有恢复真正的意识。

不过好消息是，器官移植领域最近确实也是喜讯不断。比如最近世界上的首例换脸术宣告成功了。另外，未来人们很有可能能够用上从转基因的猪身上培养的器官。

作者：Sy Mukherjee

译者：贾政景

The Internet was abuzz on Friday with news that famed—and controversial—Italian neurosurgeon Sergio Canavero and partner Dr. Xiaoping Ren of Harbin Medical University in China had performed the world’s first successful human head transplant(albeit with the major caveat that it was done on a corpse, raising comparisons to Dr. Frankenstein and his monster). Canavero claims the procedure was a success and a sign that full-on, presumably live head transplant surgeries are “imminent,” with the potential to help people who suffer from diseases which have caused their bodies to waste away.

But Canavero and Ren have prompted plenty of skepticism over the years from critics challenging both the scientific feasibility and ethical implications of head transplants, with some prominent doctors rejecting the notion that such a procedure is even possible. Canavero and Ren have played up reported successes in performing mice, monkey, and even rat head transplant operations.

There are, as you might imagine, a number of massive obstacles to successfully completing a head transplant surgery. Not only would head and neck tissue, nerve cells, and spinal cords have to be grafted together to create functional units; the patient going through such an extensive procedure would have to stay alive for long enough for it to work and then have to hope that his or her new body doesn’t reject the head of a biological stranger.

Considering that even groundbreaking, clinically proven biological re-engineering—like new genetic technologies which involve manipulating blood cancer patients’ immune cells into becoming cancer killers before re-inserting them into the body—can cause serious, toxic side effects, it’s an open question what the long-term effects of an entirely new head and brain would have on a body (or vic versa); such interactions would be highly unpredictable.

And as neuroscience Dr. Dean Burnett points out in a scathing op-ed, Canavero’s outsized claims about past successes may not exactly align with the realities of his accomplishments. For instance, Burnett notes, the monkey head transplant procedure didn’t result in a being with actual consciousness.

There have, however, been other kinds of recent milestones in the transplant space, including one of the most extensive face transplants ever done and the prospect of human organ donations from genetically modified pigs.