How to grow a bone - Nina Tandon

如何培育骨頭？－尼娜·坦登

譯者: Kelly Liu 審譯者: Yamei Huang

Can you grow a human bone outside the human body?

我們是否能在人體外培養骨頭呢？

The answer may soon be yes,

在不久以後，這極可能成真，

but before we can understand how that's possible,

在了解這可能性之前 我們應該先看一下，

we need to look at how bones grow naturally inside the body.

骨頭如何在人體中自然的生長。

Most bones start in a growing fetus as a soft, flexible cartilage.

在胎兒時期，大多數的骨頭是柔軟 且富有彈性的軟骨。

Bone-forming cells replace the cartilage with a spongy mineral lattice

製造骨頭的細胞以鈣和 磷酸鹽所組成的

made of elements like calcium and phosphate.

海綿狀礦物晶格取代軟骨。

This lattice gets harder, as osteoblasts,

造骨細胞， 是一種專門製造骨頭的細胞，

which are specialized bone-forming cells,

能使更多的礦物質沉積， 讓晶格變的更硬，

deposit more mineral, giving bones their strength.

賦予骨頭強度和韌性。

While the lattice itself is not made of living cells,

雖然晶格本身 不是由活的細胞所組成，

networks of blood vessels, nerves and other living tissues

但由血管、神經及 其他活的組織所構成的網絡

grow through special channels and passages.

皆通過其建構的特殊通路及通道。

And over the course of development,

而在整個成長的過程當中，

a legion of osteoblasts reinforce the skeleton

眾多的造骨細胞強化了骨骼

that protects our organs, allows us to move,

保護內臟，讓我們能活動，

produces blood cells and more.

製造血球等等。

但是光靠造骨這項最初的功能

But this initial building process alone

is not enough to make bones strong and functional.

並不足以讓骨頭 變得強韌且具功能性。

If you took a bone built this way,

假設你用這樣製造的骨頭，

attached muscles to it,

加上肌肉，

and tried to use it to lift a heavy weight,

然後試著舉一重物，

the bone would probably snap under the strain.

骨頭可能會在應變的作用下斷裂。

This doesn't usually happen to us

然而這卻不常發生在我們身上

because our cells are constantly reinforcing

因為我們的細胞會不斷的強化

and building bone wherever they're used,

在使用過的地方製造新的骨頭，

a principle we refer to as Wolff's Law.

這就是我們所謂的沃爾夫定律。

However, bone materials are a limited resource

然而，用來製造骨頭 的材料來源卻是有限的

and this new, reinforcing bone

所以，這全新加強版的骨頭

can be formed only if there is enough material present.

要有充足的材料下才能形成。

Fortunately, osteoblasts, the builders,

還好，負責製造骨頭的造骨細胞

have a counterpart called osteoclasts, the recyclers.

有個功能相反， 專職回收的破骨細胞。

Osteoclasts break down the unneeded mineral lattice using acids and enzymes

破骨細胞以酸和酵素酶 將無用的礦物晶格拆解

so that osteoblasts can then add more material.

這樣就可以提供 更多原料給造骨細胞。

One of the main reasons astronauts must exercise constantly in orbit

而太空人為何 要在太空軌道中不斷運動的主因

is due to the lack of skeletal strain in free fall.

是因為在無重力狀態下 骨骼缺乏應力作用。

As projected by Wolff's Law,

如沃爾夫定律所示， 在缺乏應力作用的情況下

that makes osteoclasts more active than osteoblasts,

破骨細胞會比造骨細胞要來的活躍，

resulting in a loss of bone mass and strength.

會造成骨質密度和骨頭強度的流失。

When bones do break, your body has an amazing ability

當骨頭斷裂， 你的身體有個驚人的機制

to reconstruct the injured bone as if the break had never happened.

將破損的骨頭修復， 就像斷裂從未發生。

Certain situations, like cancer removal,

但是像一些特殊情況，如癌症切除，

traumatic accidents,

創傷，或是基因缺陷所造成的傷害，

and genetic defects exceed the body's natural ability for repair.

超過身體自我修復的能力。

Historical solutions have included filling in the resulting holes with metal,

過去用來填充骨頭破洞的物質 包括金屬、

animal bones,

動物的骨頭，

or pieces of bone from human donors,

或捐贈者的部分骨頭，

but none of these are optimal as they can cause infections

但這些都不是最佳的方案， 因可能造成感染

or be rejected by the immune system,

或被患者的免疫系統排斥，

and they can't carry out most of the functions of healthy bones.

或不能執行健康骨頭的大部分任務。

An ideal solution would be to grow a bone made from the patient's own cells

最理想的方法是 用患者本身的細胞培育骨頭

that's customized to the exact shape of the hole,

專門為骨頭破洞形狀製作的。

and that's exactly what scientists are currently trying to do.

這正是科學家們在嘗試的作法。

Here's how it works.

作法如下。

First, doctors extract stem cells from a patient's fat tissue

首先，醫生們將病人的 幹細胞從脂肪組織取出

and take CT scans to determine the exact dimensions of the missing bone.

用斷層掃描來確認 骨頭破損部位的尺寸大小。

They then model the exact shape of the hole,

用得到的尺寸製造模型，

either with 3D printers,

用 3D 列印的技術，

or by carving decellularized cow bones.

或是雕刻脫細胞的牛骨。

Those are the bones where all of the cells have been stripped away,

就是將全部細胞脫除後的骨頭，

leaving only the sponge-like mineral lattice.

留下如海綿狀的礦物晶格。

They then add the patient's stem cells to this lattice

接著， 他們將患者的幹細胞加在晶格上，

and place it in a bioreactor,

將它們放入生物反應器中，

a device that will simulate all of the conditions found inside the body.

一種可模擬體內 各種環境條件的機器。

Temperature, humidity, acidity and nutrient composition

溫度、濕度、酸度和營養成分

all need to be just right for the stem cells to differentiate

都必須調整到剛剛好， 適合幹細胞進行分化

into osteoblasts and other cells,

成為造骨細胞和其他細胞，

colonize the mineral lattice,

在晶格上生長，

and remodel it with living tissue.

再用活的細胞組織來塑造。

But there's one thing missing.

但我們遺漏了一件事。

Remember Wolff's Law?

還記得沃爾夫定律嗎？

An artificial bone needs to experience real stress,

人造骨頭必須經歷真正的壓力，

or else it will come out weak and brittle,

要不然只會變得脆弱易碎，

so the bioreactor constantly pumps fluids around the bone,

所以生物反應器 會持續在骨頭周圍灌入液體，

and the pressure tells the osteoblasts to add bone density.

製造出的壓力 讓造骨細胞增進骨頭密度，

Put all of this together, and within three weeks,

把所有加在一起，約等 3 週，

the now living bone is ready to come out of the bioreactor

活體骨頭在反應器中 已準備好被取出。

and to be implanted into the patient's body.

移植到患者的體內。

While it isn't yet certain that this method will work for humans,

雖然未能確認此方法 是否適用於人體，

lab grown bones have already been successfully implanted in pigs

實驗室培養的骨頭 已成功移植在豬

and other animals,

以及其他動物的身上，

and human trials may begin as early as 2016.

預計最早會在 2016 年進行人體實驗