Want a Whole New Body? Ask This Flatworm How | Deep Look

Planarians are tiny googly-eyed flatworms with an uncanny ability: They can regrow their entire bodies, even a new head. So how do they do it?

DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. Explore big scientific mysteries by going incredibly small.

Nelson Hall wants you to know that the googly-eyed flatworm he just sliced into four pieces is going to be OK.

Three of the flatworm’s four pieces have started to wriggle away from each other and its head is moving in circles under Hall’s microscope. “The head will just go off and do its own thing,” said Hall, a doctoral student of bioengineering at Stanford University.

But in three weeks, the head, as well as the other pieces, will each have grown into a complete flatworm just like the one Hall sliced up, dark brown and about a half-inch long.

Hall and researchers around the world are hard at work trying to understand how these flatworms, called planarians, use powerful stem cells to regenerate their entire bodies, an ability humans can only dream of.

Animals like starfish, salamanders and crabs can regrow a tail or a leg. Planarians, on the other hand, can regrow their entire bodies – even their heads, which only a few animals can do.

---What is the difference between healing and regeneration?
When we suffer a severe injury, the best we can hope for is that our wounds will heal. “Healing is more like closing the wound and cleaning debris. It’s too short of a process to have tissue replacement,” said Hall. “Regeneration is replacing the tissue that was lost.”

---What are pluripotent stem cells?
If planarians can regrow body parts, why can’t we? Key to planarians’ regenerative ability are powerful cells called pluripotent stem cells, which make up one-fifth of their bodies and can grow into every new body part. Humans only have pluripotent stem cells during the embryonic stage, before birth. After that, we mostly lose our ability to sprout new organs.

“We have a couple of tissues that can regenerate, like the liver, the outer layers of the skin and the inner layers of the intestine, and the bone marrow,” said Dr. Stephen Badylak, Deputy Director of the McGowan Institute for Regenerative Medicine at the University of Pittsburgh. “But the way we heal most tissues is by forming scar tissue.”

Scientists hope that studying planarians could lead to treatments for humans in which our stem cells could be coaxed one day to regrow severed limbs or sick organs.

---How to grow a fingertip.
Doctors are limited in what they can currently do to help people who lose a limb or part of one. Badylak, who doesn’t study planarians, has developed a treatment at the University of Pittsburgh that helps patients regrow their fingertips after an accident.

He applies a powder made of animal collagen and substances that stimulate cells to grow, to help form a scaffold that attracts stem cells from the parts of the nail that weren’t cut off. The stem cells regrow the fingertip, which isn’t identical to the one that was cut off, but is functional.

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#deeplook #planaria #flatworm

[gabrielaquiros]

Hi Deep Look fans! I produced this episode. Here are the answers to a few questions you have asked. Nelson Hall, a doctoral student at Stanford University who studies planarians provided me with the answers below. Thanks for watching! -Gabriela

1- What would happen if a planarian were cut lengthwise, rather than from side to side, as we show in the video?
It would take a little longer to regenerate, but it would regenerate all the same.

2- How do planarians reproduce?
Some reproduce sexually, by mating and laying eggs. Others reproduce asexually, by breaking off a piece of their body from which a new planarian grows.

3- How do planarians die?
Hall says they can die from infection or starvation. “If you really want to kill a worm, ” he says, “you can dehydrate it, keep it over 30 degrees Celsius, freeze it, or use toxic chemicals. I’m sure you could get creative with how to kill planarians, but cutting (within reason) and aging will not do it.”

4- If you put a planarian in a blender, would each bit regenerate?
“Unfortunately, probably not, ” Hall says. “A planarian in a blender will just produce very dead worm mush.”

5- What is the smallest amount of planarian that can regenerate?
“If the wound can close and if the remaining fragment has at least one stem cell, ” says Hall, then it can grow a whole new planarian.  

6- Are planarians immortal?
If none of the situations described above were to happen, then yes, a planarian could be immortal. For asexual planarians – the ones that reproduce by breaking off a piece of their bodies and growing a new planarian – there’s no evidence that they age, Hall says. For planarians that reproduce sexually, there may be a slight decline in fertility with age.

[jimmypgp]

Their faces are just like:

• •

[egg]

Planarian: I'm so lonely...
Scientist: *chops planarian in half*
Planarian: ARGH oh hey....

[goose]

"It doesn't even hurt"

Flatworm: *screams in high pitch*

[smae]

Imagine being born like this. Hey mom, how was I born?
Mom: oh I cut off my leg and you grew

[lexdumas]

Planarian: I'm alone
Scientist: I got you fam
Planarian: Nice

[dadp]

Me: *Kills planarian*
Planarian: *Bish I'm 5 of them now.*

[Toastmaster_]

I suppose you could consider the guy who cut it up a disciplanarian

[brambleberry]

My boyfriend’s mum is a scientist working on flatworm research. She showed me her little tub of flatworms she uses to research & it’s so fascinating

[hcildwold]

Planarian's reason for developing this ability

-Mom? I don't have friends at school:(
-Huhh.. hold on let me get a knife.

[ConcealedWeaponry]

"Planarians are the ONLY animals that can regrow a head, so why can't we?"

*Because we don't want a copy of ourselves running around.*

[mrtails]

"I promise, everything's gonna be OK."

*cuts into 4 pieces*

[fluufymon]

If we as humans kept those cells when we grow older, wouldnt that mean that if an arm got cut off, not only would the arm grow back, but the arm that was cut off would grow a new body?

[miair]

Am I the only one thinks that their faces look cute?

[Dinoman]

Murderer: *slashes planarian in half*
Planarian: Oh, no. Now I have a brother...

[DragonSlayerknowsdawae]

Thanos: *Goes for the head*


Flatworm: I'm about to end this purple big-chin's whole career

[iwillsueminyoongibecausehe]

“don’t worry it won’t hurt”
worm be like
Oh no!
3 weeks later
anyways

[nahil]

TO SHOW YOU THE POWER OF STEM CELLS






I SAWED THIS PLANARIA IN HALF

[JcDaFloof]

Planarian: - gets chopped up -
3 weeks later
Planarian #1: Ayyy my bruddas!
All other Planarians: Ayyyy!

[goldboss]

Me: im bored
*cuts off my own hand and waits overnight*
Other me: hey
Me: hey