科學家發現年輕血液具有返老還童的神奇力量大綱

Two teams of scientists published studies on Sunday showing that blood from young mice reverses aging in old mice, rejuvenating their muscles and brains. As ghoulish as the research may sound, experts said that it could lead to treatments for disorders like Alzheimer's disease and heart disease.

兩個科學家團隊週日發佈的研究表明，幼齡鼠的血液能逆轉老齡鼠的衰老，讓它們的肌肉和大腦恢復活力。相關研究聽上去可能令人毛骨悚然，專家卻表示，這可能會有助於阿爾茨海默氏徵和心臟病的治療。

"I am extremely excited," said Rudolph Tanzi, a professor of neurology at Harvard Medical School, who was not involved in the research. "These findings could be a game changer."

“我非常激動，”未參與前述研究的哈佛大學醫學院(Harvard Medical School)神經學教授魯道夫·坦齊(Rudolph Tanzi)說，“這些發現可能會帶來鉅變。”

The research builds on centuries of speculation that the blood of young people contains substances that might rejuvenate older adults.

這項研究是基於一個流傳了數百年的猜測，即年輕人的血液可能含有能讓老年人恢復活力的物質。

In the 1950s, Clive M. McCay of Cornell University and his colleagues tested the notion by delivering the blood of young rats into old ones. To do so, they joined rats in pairs by stitching together the skin on their flanks. After this procedure, called parabiosis, blood vessels grew and joined the rats' circulatory systems. The blood from the young rat flowed into the old one, and vice versa.

上世紀50年代，康奈爾大學(Cornell University)的克萊夫·M·麥凱(Clive M. McCay)和同事曾將幼齡鼠的血液輸入老齡鼠體內，藉此檢驗這一觀念。爲了做到這一點，他們將兩隻大鼠的側腹皮膚縫在一起，使它們連接起來。經過被稱作異種共生的這一步後，血管生長出來，兩隻老鼠的循環系統融合在了一起。幼齡鼠的血液流入了老齡鼠的體內，老齡鼠的血也流進了幼鼠。

Later, Dr. McCay and his colleagues performed necropsies and found that the cartilage of the old rats looked more youthful than it would have otherwise. But the scientists could not say how the transformations happened. There was not enough known at the time about how the body rejuvenates itself.

後來，麥凱博士和同事解剖了老鼠的屍體，發現老齡鼠的軟骨看起來比它未經實驗的應有狀態更年輕。但這些科學家無法說明這種變化是如何發生的。當時，人們對身體恢復活力的方式還沒有足夠的認識。

It later became clear that stem cells are essential for keeping tissues vital. When tissues are damaged, stem cells move in and produce new cells to replace the dying ones. As people get older, their stem cells gradually falter.

後來，人們清楚地認識到，幹細胞對保持組織的活力至關重要。組織受損時，幹細胞會進入，生成新細胞來取代失去活力的老細胞。隨着年齡的增長，人的幹細胞會逐漸衰退。

In the early 2000s, scientists realized that stem cells were not dying off in aging tissues.

本世紀初，科學家意識到，幹細胞並沒有在日漸衰老的組織中逐漸消亡。

"There were plenty of stem cells there," recalled Thomas A. Rando, a professor of neurology at Stanford University School of Medicine. "They just don't get the right signals."

“幹細胞是很多的，”斯坦福大學醫學院(Stanford University School of Medicine)神經學教授托馬斯·A·蘭多(Thomas A. Rando)回憶說，“它們只是沒有接收到正確的信號而已。”

Dr. Rando and his colleagues wondered what signals the old stem cells would receive if they were bathed in young blood. To find out, they revived Dr. McCay's experiments.

蘭多博士和他的同事想要知道，如果沐浴在年輕的血液之中，老的幹細胞會收到什麼信號。爲了找到答案，他們重新進行了麥凱博士的實驗。

The scientists joined old and young mice for five weeks and then examined them. The muscles of the old mice had healed about as quickly as those of the young mice, the scientists reported in 2005. In addition, the old mice had grown new liver cells at a youthful rate.

科學家們將老齡鼠和幼齡鼠連接在一起，五週之後再去觀察它們。他們在2005年通報稱，老齡鼠的肌肉癒合速度幾乎和幼齡鼠一樣快。此外，老齡鼠以幼齡鼠的速度長出了新的肝細胞。

The young mice, on the other hand, had effectively grown prematurely old. Their muscles had healed more slowly, and their stem cells had not turned into new cells as quickly as they had before the procedure.

另一方面，幼齡鼠實實在在地未老先衰了。它們的肌肉癒合得更慢，幹細胞轉化成新細胞的速度也不如實驗之前快。

The experiment indicated that there were compounds in the blood of the young mice that could awaken old stem cells and rejuvenate aging tissue. Likewise, the blood of the old mice had compounds that dampened the resilience of the young mice.

這個實驗表明，幼齡鼠的血液含有一些化合物，這些化合物可能會喚醒老的幹細胞，讓日漸衰老的組織恢復活力。同理，老齡鼠的血液含有抑制幼齡鼠活力的化合物。

Amy J. Wagers, a member of Dr. Rando's team, continued to study the blood of young mice after she moved in 2004 to Harvard, where she is an associate professor. Last year, she and her colleagues demonstrated that it could rejuvenate the hearts of old mice.

蘭多博士的團隊成員埃米·J·韋傑斯(Amy J. Wagers)在2004年進入哈佛，之後繼續研究幼齡鼠的血液。她現在是哈佛的副教授。去年，她和同事證明，幼齡鼠的血液可以恢復老齡鼠心臟的活力。

To pinpoint the molecules responsible for the change, Dr. Wagers and her colleagues screened the animals' blood and found that a protein called GDF11 was abundant in young mice and scarce in old ones. To see if GDF11 was crucial to the parabiosis effect, the scientists produced a supply of the protein and injected it into old mice. Even on its own, GDF11 rejuvenated their hearts.

爲了確定這種變化究竟與哪種分子相關，韋傑斯和同事對老鼠的血液進行了測試，發現幼齡鼠體內含有大量名爲GDF11的蛋白質，而這種蛋白質在老齡鼠體內較少。爲了確定GDF11是不是對異種共生效應的關鍵因素，科學家制造了一些這種蛋白質，並將它注入老齡鼠體內。單是GDF11就能使它們的心臟恢復活力。

Dr. Wagers and her colleagues wondered whether GDF11 was responsible for the rejuvenation of other tissues. In the current issue of the journal Science, they report an experiment on skeletal muscle in mice. They found that GDF11 revived stem cells in old muscles, making old mice stronger and increasing their endurance.

韋傑斯和同事想知道GDF11是否起到了使其他組織恢復活力的作用。他們在本期《科學》(Science)雜誌中闡述了針對老鼠骨骼肌肉的一項實驗，實驗發現GDF11能使老齡鼠肌肉中的幹細胞恢復活力，增強老齡鼠的體質，延長它們的壽命。

At Stanford, researchers were investigating whether the blood of young mice altered the brains of old mice. In 2011, Saul Villeda, then a graduate student, and his colleagues reported that it did. When old mice received young blood, they had a burst of new neurons in the hippocampus, a region of the brain that is crucial for forming memories.

斯坦福大學(Stanford)的研究人員曾對幼齡鼠的血液是否能改變老齡鼠的腦功能進行過研究。2011年，當時還是研究生的索爾·比列達(Saul Villeda)和同事表示，答案是肯定的。接受幼齡鼠的血液之後，老齡鼠的海馬體就會大量產生新的神經元。海馬體是大腦中的一個區域，對記憶的形成具有關鍵作用。

In a study published Sunday in the journal Nature Medicine, Dr. Villeda, now a faculty fellow at the University of California, San Francisco, and his colleagues unveiled more details of what young blood does to the brains of old mice.

在週日發表於《自然醫學》(Nature Medicine)雜誌的一篇文章中，現已成爲加州大學舊金山分校(University of California, San Francisco)研究員的比列達和同事披露了更多細節，闡述了幼齡鼠的血液對老齡鼠大腦造成的影響。

After parabiosis, Dr. Villeda and his colleagues found that the neurons in the hippocampus of the old mice sprouted new connections. They then moved beyond parabiosis by removing the cells and platelets from the blood of young mice and injecting the plasma that remained into old mice. That injection caused the old mice to perform far better on memory tests.

比列達和同事發現，異種共生過程之後，老齡鼠海馬體中的神經元長出了新的聯結。然後，除了異種共生之外，他們還移除了幼齡鼠血液中的細胞和血小板，再把剩下的血漿注入老齡鼠體內。這種注射大幅改善了老齡鼠在記憶測試中的表現。

Dr. Wagers's team has been investigating a specific region of the brain involved in perceiving smells.

韋傑斯的團隊一直在對大腦中與嗅覺相關的一個特殊區域進行研究。

In a second study in Science, the team reports that parabiosis spurred the growth of blood vessels in the brain. The new blood supply led to the growth of neurons and gave older mice a sharper sense of smell.

他們的團隊在《科學》刊載的另一篇文章中指出，異種共生能刺激腦血管的生長。新的血液能促進神經元的生長，讓老齡鼠具有更靈敏的嗅覺。

After linking the GDF11 protein to the rejuvenation of skeletal muscle and the heart, Dr. Wagers and her colleagues studied whether the protein was also responsible for the changes in the brain. They injected GDF11 alone into the mice and found that it spurred the growth of blood vessels and neurons in the brain, although the change was not as large as that from parabiosis.

將GDF11蛋白質與骨骼肌肉和心臟的復甦聯繫起來以後，韋傑斯和同事還對這種蛋白質是否與腦部變化有關進行了研究。他們對老鼠注射了單一的GDF11，然後發現它促進了腦部血管和神經元的生長，雖然相關變化並不像異種共生那麼明顯。

"There's no conflict between the two groups, which is heartening," said Dr. Richard M. Ransohoff, director of the Neuroinflammation Research Center at the Cleveland Clinic.

克利夫蘭醫學中心神經炎症研究中心(Neuroinflammation Research Center at the Cleveland Clinic)負責人理查德·M·蘭索霍夫博士(Dr. Richard M. Ransohoff)稱，“兩個團隊的發現沒有衝突，這很令人振奮。”

Dr. Ransohoff and others hope the experiments on mice will lead to studies on people to see if the human version of GDF11, or other molecules in the blood of young people, has a similar effect on older adults.

蘭索霍夫和其他一些人都希望，以小鼠爲對象的實驗能夠衍生以人爲對象的研究，以探明人類版的GDF11或年輕人血液中的其他分子能否對老年人產生類似影響。

"We can turn back the clock instead of slowing the clock down," said Dr. Toren Finkel, director of the Center for Molecular Medicine at the National Heart, Lung and Blood Institute. "That's a nice thought if it pans out."

“我們可以讓時間倒流，不只是讓它放慢腳步，”美國國家心臟、肺和血液研究所(National Heart, Lung and Blood Institute)分子醫學研究中心負責人託倫·芬克爾博士(Dr. Toren Finkel)說。“如果能成功，這將是個不錯的想法。”