How to grow a bone - Nina Tandon
-
0:07 - 0:10Can you grow a human bone
outside the human body? -
0:10 - 0:12The answer may soon be yes,
-
0:12 - 0:15but before we can understand
how that's possible, -
0:15 - 0:19we need to look at
how bones grow naturally inside the body. -
0:19 - 0:24Most bones start in a growing fetus
as a soft, flexible cartilage. -
0:24 - 0:28Bone-forming cells replace the cartilage
with a spongy mineral lattice -
0:28 - 0:31made of elements like calcium
and phosphate. -
0:31 - 0:33This lattice gets harder,
as osteoblasts, -
0:33 - 0:36which are specialized bone-forming cells,
-
0:36 - 0:39deposit more mineral,
giving bones their strength. -
0:39 - 0:42While the lattice itself
is not made of living cells, -
0:42 - 0:45networks of blood vessels, nerves
and other living tissues -
0:45 - 0:48grow through special channels
and passages. -
0:48 - 0:49And over the course of development,
-
0:49 - 0:52a legion of osteoblasts
reinforce the skeleton -
0:52 - 0:55that protects our organs,
allows us to move, -
0:55 - 0:57produces blood cells and more.
-
0:57 - 1:00But this initial building process alone
-
1:00 - 1:03is not enough to make bones
strong and functional. -
1:03 - 1:05If you took a bone built this way,
-
1:05 - 1:07attached muscles to it,
-
1:07 - 1:09and tried to use it
to lift a heavy weight, -
1:09 - 1:13the bone would probably snap
under the strain. -
1:13 - 1:15This doesn't usually happen to us
-
1:15 - 1:17because our cells
are constantly reinforcing -
1:17 - 1:20and building bone wherever they're used,
-
1:20 - 1:23a principle we refer to as Wolff's Law.
-
1:23 - 1:26However, bone materials
are a limited resource -
1:26 - 1:28and this new, reinforcing bone
-
1:28 - 1:33can be formed only if
there is enough material present. -
1:33 - 1:36Fortunately, osteoblasts, the builders,
-
1:36 - 1:40have a counterpart
called osteoclasts, the recyclers. -
1:40 - 1:45Osteoclasts break down the unneeded
mineral lattice using acids and enzymes -
1:45 - 1:48so that osteoblasts can then
add more material. -
1:48 - 1:52One of the main reasons astronauts
must exercise constantly in orbit -
1:52 - 1:57is due to the lack of skeletal strain
in free fall. -
1:57 - 1:59As projected by Wolff's Law,
-
1:59 - 2:03that makes osteoclasts more active
than osteoblasts, -
2:03 - 2:06resulting in a loss
of bone mass and strength. -
2:06 - 2:09When bones do break, your body
has an amazing ability -
2:09 - 2:14to reconstruct the injured bone
as if the break had never happened. -
2:14 - 2:17Certain situations, like cancer removal,
-
2:17 - 2:18traumatic accidents,
-
2:18 - 2:23and genetic defects exceed the body's
natural ability for repair. -
2:23 - 2:27Historical solutions have included
filling in the resulting holes with metal, -
2:27 - 2:29animal bones,
-
2:29 - 2:32or pieces of bone from human donors,
-
2:32 - 2:35but none of these are optimal
as they can cause infections -
2:35 - 2:38or be rejected by the immune system,
-
2:38 - 2:41and they can't carry out most
of the functions of healthy bones. -
2:41 - 2:46An ideal solution would be to grow a bone
made from the patient's own cells -
2:46 - 2:50that's customized to
the exact shape of the hole, -
2:50 - 2:54and that's exactly what scientists
are currently trying to do. -
2:54 - 2:56Here's how it works.
-
2:56 - 3:00First, doctors extract stem cells from
a patient's fat tissue -
3:00 - 3:05and take CT scans to determine
the exact dimensions of the missing bone. -
3:05 - 3:08They then model the exact
shape of the hole, -
3:08 - 3:09either with 3D printers,
-
3:09 - 3:12or by carving decellularized cow bones.
-
3:12 - 3:15Those are the bones where all of the cells
have been stripped away, -
3:15 - 3:18leaving only the sponge-like
mineral lattice. -
3:18 - 3:21They then add the patient's stem cells
to this lattice -
3:21 - 3:23and place it in a bioreactor,
-
3:23 - 3:28a device that will simulate all
of the conditions found inside the body. -
3:28 - 3:31Temperature, humidity, acidity
and nutrient composition -
3:31 - 3:35all need to be just right for
the stem cells to differentiate -
3:35 - 3:37into osteoblasts and other cells,
-
3:37 - 3:39colonize the mineral lattice,
-
3:39 - 3:42and remodel it with living tissue.
-
3:42 - 3:44But there's one thing missing.
-
3:44 - 3:45Remember Wolff's Law?
-
3:45 - 3:48An artificial bone needs
to experience real stress, -
3:48 - 3:51or else it will come out weak and brittle,
-
3:51 - 3:55so the bioreactor constantly pumps
fluids around the bone, -
3:55 - 3:59and the pressure tells the osteoblasts
to add bone density. -
3:59 - 4:02Put all of this together,
and within three weeks, -
4:02 - 4:05the now living bone is ready
to come out of the bioreactor -
4:05 - 4:08and to be implanted
into the patient's body. -
4:08 - 4:12While it isn't yet certain that
this method will work for humans, -
4:12 - 4:15lab grown bones have already been
successfully implanted in pigs -
4:15 - 4:17and other animals,
-
4:17 - 4:21and human trials may begin
as early as 2016.
- Title:
- How to grow a bone - Nina Tandon
- Description:
-
View full lesson: http://ed.ted.com/lessons/how-to-grow-a-bone-nina-tandon
Can you grow a human bone outside the human body? The answer may soon be yes. Nina Tandon explores the possibility by examining how bones naturally grow inside the body, and illuminating how scientists are hoping to replicate that process in a lab.
Lesson by Nina Tandon, animation by Giant Animation Studios.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:37
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