英国科学家用干细胞成功培育出世界第一个人造肝脏

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英国科学家用干细胞成功培育出世界第一个人造肝脏

据英国《每日邮报》31日报道，英国科学家用干细胞成功培育出世界第一个人造肝脏，这是医学界的一项巨大突破，将来有一天，我们将会通过这种方法为移植提供完整的器官。

现在科学家培育出的这种“袖珍型肝脏”只有一分硬币大小，但这项技术经过发展就能创造出与人类肝脏大小一样的人造肝脏，且功能齐全。纽卡斯尔大学的科研人员将它称 之为“惊喜瞬间”，这个肝脏是用刚出生几分钟的婴儿的脐带血培育出的，可被用来进行新药物试验，例如最近进行的“象人”药物试验，以防不幸事件的发生。另外，利用实验室培育的肝组织进行药物试验还能减少动物实验的数量。

专家预计，在5年之内，我们就能利用这些人造组织来修复因受伤、疾病、过度饮酒和服用过量退烧药扑热息痛造成的肝脏损伤。在15年内，我们可以利用实验室培育出的肝脏器官进行完整的肝脏移植术。

这种肝组织是利用从脐带血中提取的 干细胞培育出来，干细胞是动物和人体内一种具有特殊功能的细胞，它能分化成不同的组织器官。纽卡斯尔大学的科学家与美国专家合作，在婴儿出生几分钟后，成功将干细胞从脐带血中分离出来。之后，他们将分离出的干细胞放入“生物反应器”中。生物反应器是由美国宇航局研发的，原来是用作模拟失重状态的影响。在生物反应器中的干细胞不会受到重力的影响，因此比通常情况下增殖更快。科研人员还要加入各种荷尔蒙和化学药品，诱导干细胞分裂成肝组织。这样，直径不到一英寸的微小肝组织就被成功培育出来。然而，研究人员还需要把它尽快培育成更大的组织，最终创造出可移植到病人体内的功能齐全的肝脏。

纽卡斯尔大学的科学家认为，不出两年，这种组织就可被用来试验新药物。现在，新药物都是先在试管中进行测试，然后再在动物身上进行试验，最后才用于人类。但这个程序也无法确保人类的绝对安全。今年初期进行的诺斯威克公园药物试验就产生了痛苦的结果，6名健康的年轻志愿者为此差点丢掉生命。不过，在新药用于人类前，先利用实验室培育的人类组织进行测试能消除各种安全隐患。

研究人员设想，人造肝组织将被用来满足患者对肝移植的需求，就像透析仪被用来治疗肾功能衰竭一样。这项技术将利用肝脏非凡的能力迅速更新自己。以后肝病患者移植的这种人造肝脏的大小与人类肝脏一样且各种功能齐全。他们只需在几个月中每天进行几次透析，患者肝脏的损伤部位就能自行修复，重新长出新组织。这种技术的好处是，患者无需将宝贵的时间浪费到寻找合适移植捐赠者上。

科学家有望在15年内培育出完整的肝脏，为那些肝脏损坏到无法修复的患者进行移植。此外，它还有望满足人们对完整肝脏移植的需要。但是，要在实验室中培育出适合移植的完整肝脏还需要很多年。(杨孝文）

-链接

　　人造肝脏“四部曲”

　　据悉，这种在实验室中培育人体肝脏的方法总共分为四个步骤：

　　第一步，利用试管从出生仅几分钟的婴儿脐带血中分离出干细胞；

　　第二步，将这些干细胞放入一个“生物反应器”之中。这个由美国宇航局开发的电子装置可以在地面上模拟出零重力下的实验环境，而通常在失重的环境中，细胞分裂繁殖的速度要比常态下快得多；

　　第三步，在细胞繁殖的过程中，科研人员适时加入各种荷尔蒙和化学物质，从而诱使干细胞转化成为肝脏组织；

　　第四步，继续培育得到的“迷你肝脏”，使其生长为一块重量约为1.4公斤，体积约为23厘米X15厘米X13厘米的完整肝脏。

　　虽然这个肝脏还难以与普遍意义上的肝脏相提并论，它的直径只有不到2.5厘米，但是研究人员相信，假以时日，他们终将能够培植出大的肝脏组织，最终将其应用于临床治疗。不过，也有专家警告说，人造器官研究成果在从实验室进入手术室之前，仍有很多工作要做。

　　-展望

　　15年内造完整肝脏

　　对于纽卡斯尔大学科学家在人工培育人体肝脏方面取得的突破性进展，肝脏疾病专家纷纷感到欢欣鼓舞。“英国肝脏基金”的负责人阿里森·罗杰斯表示：“干细胞技术预示着疾病治疗领域的一大进步。而在治疗肝脏疾病方面，它将拥有巨大的潜力。”

　　据初步预计，5年之内，人造肝脏组织就可以用于修复由于外伤、疾病、酗酒和药物过量造成的肝脏损伤。而在未来15年内，科学家们有望在实验室中培育出完整的可供移植的人体肝脏。

　　试药危险将终结

　　众所周知，目前任何一种新型药物都是首先在试管里检测，然后进行动物试验，最后再做人类临床试验。整个过程既复杂又危险。今年3月，在英国伦敦进行的一次药物试验中，6名健康的年轻志愿者由于肝脏等器官受到严重损害，结果其中一名试药人的脑袋肿成了平时的3倍大，惨变“试药象人”，目前仍在接受治疗。

　　如今有了实验室培育出来的“人造肝脏”，科学家们预计两年内可以用它进行新型药物检测，从而避免了活体试验的高风险。

liver411

British scientists grow human liver in a laboratory

By FIONA MacRAE, Science Reporter Last updated at 12:32pm on 31st October 2006

Reader comments (36)

British scientists have grown the world's first artificial liver from stem cells in a breakthrough that will one day provide entire organs for transplant.

The technique that created the 'mini-liver', currently the size of a one pence piece, will be developed to create a full-size functioning liver.

Described as a 'Eureka moment' by the Newcastle University researchers, the tissue was created from blood taken from babies' umbilical cords just a few minutes after birth.

As it stands, the mini organ can be used to test new drugs, preventing disasters such as the recent 'Elephant Man' drug trial. Using lab-grown liver tissue would also reduce the number of animal experiments.

Within five years, pieces of artificial tissue could be used to repair livers damaged by injury, disease, alcohol abuse and paracetamol overdose.

And then, in just 15 years' time, entire liver transplants could take place using organs grown in a lab.

The development provides fresh hope for the hundreds of Britons in dire need of a new liver each year.

There are currently 336 patients waiting for a liver transplant - the type of operation performed on George Best. However, in 2004, 72 people died waiting for a suitable donor.

The liver tissue is created from stem cells - blank cells capable of developing into different types of tissue - found in blood from the umbilical cord.

Working in collaboration with experts from the US, the Newcastle scientists succeeded in separating out the stem cells from blood removed from the umbilical cord minutes after birth.

They are then placed in a 'bioreactor' - a piece of electrical equipment developed by NASA to mimic the effects of weightlessness. Inside this, the freedom from the force of gravity allows them to multiply more quickly than usual.

Then, various hormones and chemicals are added to coax the stem cells into turning into liver tissue.

So far, tiny pieces of tissue, less than an inch in diameter have been created.

However, in time, it should be possible to create larger and larger pieces of tissue, eventually creating sections capable of being transplanted into sick patients.

The Newcastle scientists believe that within two years the tissue could be used to test new drugs.

Currently, new drugs are tested in the test tube, before being tried out first on animals and then on humans.

However, the procedure is not foolproof, as was made painfully clear by the Northwick Park drugs trial earlier this year in which six healthy young volunteers were left fighting for their lives.

Using lab-grown human tissue could iron out any difficulties before new drugs are given to humans.

Colin McGuckin is professor of regenerative medicine at Newcastle University. He said: "We take the stem cells from the umbilical cord blood and make small mini-livers.

"We then give them to pharmaceutical companies and they can use them to test new drugs on.

"It could prevent the situation that happened earlier this year when those six patients had a massive reaction to the drugs they were testing."

Using mini-livers could also cut down on the number of animal experiments.

Within five years, the artificial liver could be used to directly benefit people's health.

The researchers envisage sections of artificial liver being used to keep patients needing liver transplants alive - in much the same way as a dialysis machine is used to treat kidney failure.

This technique would take advantage of the liver's remarkable ability to quickly regenerate itself.

The patient would be hooked up to an artificial liver which would take over all the functions usually carried out by their own liver.

With several 'dialysis' sessions a day over a period of several months, the patient's own liver would be afforded enough resting time to regenerate and repair any damage.

Alternatively, vital months could be bought in search for a suitable donor for transplant.

It is hoped that within 15 years, it will be possible to create sections of liver suitable for transplant into the body of those whose livers have been damaged beyond repair.

In many cases, this would replace the need for an entire liver transplant.

However, it would then be several more years before whole livers could be created in a lab for transplant.

While other researchers have created liver cells from stem cells from embryos, the Newcastle team are the first to create sizeable sections of tissue from stem cells from the umbilical cord.

They believe their technique is better suited to growing larger sections of tissue.

Use of cord stem cells is also more ethically acceptable than the use of embryonic stem cells - a process that leads to the death of the embryo.

The Newcastle researchers foresee a time when cord blood from millions of babies born each year is banked, creating a worldwide donor register for liver dialysis and transplant.

Computerised registers could then be created to match the cord blood with tissue type or immune system of patients with liver problems.

Already used to treat leukaemia, more than 11,000 British parents have so far chosen frozen their children's cord blood in a dozen such banks around the UK.

Prof McGuckin said: "One hundred million children are born around the world every year - that is 100 million different tissue types.

"With that number of children being born every year, we should be able to find a tissue for me and you and every other person who doesn't have stem cells banked."

Co-researcher Dr Nico Forraz said: "Our dream is that every metropolitan city would have such a bank.

"If you could type the blood all, you would have to do is dial it up on your computer and fly it from Bristol to Newcastle or even Newcastle to Kuala Lumpur."

The breakthrough has been welcomed by liver experts. However, they caution much more work is needed before the research is transferred from the lab to the operating theatre.

Professor Nagy Habib, of London's Hammersmith Hospital, said: "The stem cell is going to change the way we deliver treatment. However, it won't happen tomorrow."

Alison Rogers, Chief Executive of the British Liver Trust, said: "Stem cell technology represents a huge leap forward in treating many diseases. "With liver disease in particular it has the potential for tremendous advances."

A spokesman for UK Transplant, which runs the country's organ donor register, said: "There is lots going on in research that may have benefits for transplant patients.

"But, in the here and now, the obvious way to help these people is by more people adding their names to the organ donor register and to make their wishes known to their family."

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