Featured Research

from universities, journals, and other organizations

How a flatworm regenerates missing tissues: Pluripotent adult stem cells power planarian regeneration

Date:
May 13, 2011
Source:
Whitehead Institute for Biomedical Research
Summary:
Researchers have determined that the planarian flatworm regenerates missing tissues by using pluripotent adult stem cells. Until now, scientists could not determine whether the dividing cells in planarians, called neoblasts, are a mixture of specialized stem cells that each regenerates specific tissues, or if individual neoblasts are pluripotent and able to regenerate all tissues.

This planarian was irradiated to kill all of its dividing cells, except for rare, isolated pluripotent stem cells, called clonogenic neoblasts (cNeoblasts). Fourteen days later, a colony of cNeoblasts (dark purple dots) has a begun to spread into the planarian's tissues.
Credit: Daniel Wagner

Ever since animals, such as lizards and starfish, were observed regenerating missing body parts, people have wondered where the new tissues come from. In the case of the planarian flatworm, Whitehead Institute researchers have determined that the source of this animal's extraordinary regenerative powers is a single, pluripotent cell type.

Most advanced animals, including mammals, have a system of specialized stem cells. In humans, we have blood stem cells in our bone marrow that make blood and immune cells, skin stem cells that produce new layers of skin, and intestinal stem cells that continually renew our gut linings, to name just a few. In humans, only embryonic stem cells and germ cells are pluripotent -- with the ability to create all cell types in the body.

In the planarian flatworm Schmidtea mediterranea, certain dividing cells, called neoblasts, have long been identified as essential for the regeneration that repairs the worm's tissues. Until now, however, scientists could not determine whether neoblasts represent a mixture of specialized stem cells that each regenerates specific tissues or are themselves pluripotent and able to regenerate all tissues.

"And that question is at the heart of understanding regeneration in these animals," says Whitehead Member Peter Reddien, who is also an associate professor of biology at MIT and a Howard Hughes Medical Institute (HHMI) Early Career Scientist. "The reason it's never been possible to address this question is because we needed assays that allow us to ask what the regenerative potential of single cells is."

Using complementary methods, Dan Wagner, Irving Wang -- two graduate students in the Reddien lab and co-first authors -- and Reddien have demonstrated that adult planarians not only possess pluripotent stem cells -- known as clonogenic neoblasts (cNeoblasts) -- but that a single such cell is capable of regenerating an entire animal. Their results are published in the May 13 issue of Science.

In one method, Wagner gave planarians a dose of radiation that killed all of their dividing cells, except for rare, isolated cNeoblasts. By labeling cells for a gene expressed only in neoblasts, Wagner observed that these individual surviving cNeoblasts divided to form large colonies of cells. Wagner analyzed the colonies and found that they contained cells differentiating into neurons and intestinal cells, indicating broad developmental potential for the initiating cNeoblast. Furthermore, Wagner showed that small numbers of cNeoblasts were capable of restoring regenerative potential to entire animals.

Using another method, Wang and Reddien transplanted single cNeoblasts from one strain of planarian into lethally irradiated host planarians from a different strain, which lacked their own neoblasts and the ability to regenerate. Because the donor cells were distinguishable from the host, the researchers demonstrated that the transplanted cNeoblast multiplied, differentiated, and ultimately replaced all the host's tissues. From a single transplanted cell, the host not only regained the ability to regenerate, but was also converted to the genetic identity of the donor strain.

Because this work showed that cNeoblasts can differentiate into diverse tissue types and even replace all of the tissues in a host planarian, the researchers were able to conclude that cNeoblasts are pluripotent stem cells.

Further study of cNeoblasts could help researchers understand how stem cells can act to promote regeneration.

"This is an animal that, through evolution, has already solved the regeneration problem," says Wagner. "We're studying planarians to see how their regeneration process works. And, one day, we'll examine what are the key differences between what's possible in this animal and what's possible in a mouse or a person."

In the near future, the research group is interested in exploring the new possibilities provided by their techniques.

"Single-cell transplants have opened up a lot more experiments that we can do," says Wang. "Now that it is possible to identify and isolate single cNeoblasts, we can explore what makes these cells pluripotent."

This research was supported by the National Institutes of Health (NIH) and the Keck Foundation.

Peter Reddien's primary affiliation is with Whitehead Institute for Biomedical Research, where his laboratory is located and all his research is conducted. He is also a Howard Hughes Medical Institute Early Career Scientist and an associate professor of biology at Massachusetts Institute of Technology.


Story Source:

The above story is based on materials provided by Whitehead Institute for Biomedical Research. The original article was written by Nicole Giese. Note: Materials may be edited for content and length.


Journal Reference:

  1. Daniel E. Wagner, Irving E. Wang, Peter W. Reddien. Clonogenic Neoblasts Are Pluripotent Adult Stem Cells That Underlie Planarian Regeneration. Science, 2011; 332 (6031): 811-816 DOI: 10.1126/science.1203983

Cite This Page:

Whitehead Institute for Biomedical Research. "How a flatworm regenerates missing tissues: Pluripotent adult stem cells power planarian regeneration." ScienceDaily. ScienceDaily, 13 May 2011. <www.sciencedaily.com/releases/2011/05/110512150727.htm>.
Whitehead Institute for Biomedical Research. (2011, May 13). How a flatworm regenerates missing tissues: Pluripotent adult stem cells power planarian regeneration. ScienceDaily. Retrieved August 29, 2014 from www.sciencedaily.com/releases/2011/05/110512150727.htm
Whitehead Institute for Biomedical Research. "How a flatworm regenerates missing tissues: Pluripotent adult stem cells power planarian regeneration." ScienceDaily. www.sciencedaily.com/releases/2011/05/110512150727.htm (accessed August 29, 2014).

Share This




More Plants & Animals News

Friday, August 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Raw: Australian Sheep Gets Long Overdue Haircut

Raw: Australian Sheep Gets Long Overdue Haircut

AP (Aug. 28, 2014) Hoping to break the record for world's wooliest, Shaun the sheep came up 10 pounds shy with his fleece weighing over 50 pounds after being shorn for the first time in years. (Aug. 28) Video provided by AP
Powered by NewsLook.com
Minds Blown: Scientists Develop Fish That Walk On Land

Minds Blown: Scientists Develop Fish That Walk On Land

Newsy (Aug. 28, 2014) Canadian scientists looking into the very first land animals took a fish out of water and forced it to walk. Video provided by Newsy
Powered by NewsLook.com
Fake Dogs Scare Real Geese from Wis. Park

Fake Dogs Scare Real Geese from Wis. Park

AP (Aug. 28, 2014) Parks officials in Stevens Point, Wisconsin had a fowl problem. Canadian Geese were making a mess of a park, so officials enlisted cardboard versions of man's best friend. (Aug. 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins