Featured Research

from universities, journals, and other organizations

Flatworms provide new insight into organ regeneration and the evolution of mammalian kidneys

Date:
August 12, 2011
Source:
Stowers Institute for Medical Research
Summary:
Our bodies are perfectly capable of renewing billions of cells every day but fail miserably when it comes to replacing damaged organs such as kidneys. Using the flatworm Schmidtea mediterranea -- famous for its capacity to regrow complete animals from minuscule flecks of tissue -- as an eloquent example, researchers have demonstrated how our distant evolutionary cousins regenerate their excretory systems from scratch.

Planaria have a network of fine tubules (shown in white) running throughout their bodies. The tubules are connected to bulb-like structures called flame cells. These cells contain cilia, which move the fluids toward the excretory pores located throughout the epidermis.
Credit: Courtesy of the Sanchéz Alvarado lab, Stowers Institute for Medical Research

Our bodies are perfectly capable of renewing billions of cells every day but fail miserably when it comes to replacing damaged organs such as kidneys. Using the flatworm Schmidtea mediterranea -- famous for its capacity to regrow complete animals from minuscule flecks of tissue -- as an eloquent example, researchers at the Stowers Institute for Medical Research demonstrated how our distant evolutionary cousins regenerate their excretory systems from scratch.

Related Articles


In the process, the Stowers team led by Howard Hughes Medical Institute and Stowers investigator Alejandro Sanchéz Alvarado, Ph.D., not only established flatworms as a valuable model system to study tissue maintenance and organ regeneration but also provided new clues about the evolutionary origin of mammalian kidneys. Their study is published in the current issue of the journal Development.

"The past ten years of planaria research have shown that planarians use pretty much the same molecular toolkit for building their bodies as other animals," says first author Jochen Rink, Ph.D., formerly a postdoctoral researcher in the Sanchéz lab and now a group leader at the Max-Planck-Institute of Molecular Cell Biology and Genetics in Dresden, Germany. "Because of this fundamental similarity between all animals, understanding how a worm assembles its excretory system may very well be relevant to understanding kidney physiology and regeneration in humans," he adds.

Most animals studied in the lab fall within two main branches on the evolutionary tree of life: mice, rats, and salamanders are part of the vertebrate lineage, while fruit flies and the roundworm Ceanorhabditis elegans belong to the lineage encompassing molting animals. "People have drawn conclusions about the evolution of certain attributes by looking exclusively at these two branches," says Sanchéz Alvarado. "That's akin to trying to work out your family tree but ignoring your entire maternal lineage."

In contrast, flatworms, also known as planaria, are part of a branch that has been largely ignored by modern molecular biology. "The so called lophotrochozoa are an incredibly large and diverse group of animals we know very little about," explains Sanchéz Alvarado.

What was known is that -- unlike fruit flies and C. elegans -- planaria possess very complex excretory systems akin in many respects to mammalian kidneys. "Planarian protonephridia are so far the only invertebrate model system that combines pressure filtration with filtrate modification similar to mammalian nephrons, the basic functional unit of the kidney," explains Rink. Their anatomy, however, was not well understood.

When Rink and co-first author Hanh Thi-Kim Vu, Ph.D., a graduate student in the Sanchez Alvarado lab, analyzed their structure with the help of electron microscopy, the scientists found that planarian protonephridia are complex epithelial organs that organized in a consistent and hierarchical manner: a distal tubule branching out into proximal tubules, each of which is topped by a ciliated flame cell -- so named because under a microscope the beating of the cilia resembles a flickering candle.

But more importantly, they noticed that the endothelia forming the tubules are composed of a fixed succession of different cell types along their length reminiscent of the mammalian condition. "This suggests to us that the mammalian kidney originated before the branches split," says Sanchéz Alvarado. "The homologous structures in fruit flies and C. elegans diversified and diverged till they no longer resembled their common ancestor."

Protonephridia are distributed throughout a flatworm's body. To study their development researchers could simply cut the animals' heads off and watch how they regrew the missing body part including excretory tubules within a week. They found that protonephridial tubules originated from a precursor structure, which undergoes extensive branching morphogenesis, the same process that also shapes vertebrate organs such as lung, kidneys or mammary glands.

When Rink interfered with the expression of EGFR5, short for epidermal growth factor receptor, during the regeneration process protonephridia could no longer undergo branching morphogenesis. If he did the same in non-regenerating planaria, they were unable to maintain the structural integrity of their protonephridia, which told him that under normal conditions the organ is constantly maintained through cell renewal.

"We take it for granted that we go to bed with two sets of fully functional kidneys and that we wake up with them the next morning but we don't understand the fundamental processes that give rise to this very well choreographed maintenance of an organism's form and function," says Sanchéz Alvarado. "We can now start to use planaria as a model to begin to understand how an adult animals maintain their form and function over a very long time."

The work was funded in part by the Howard Hughes Medical Institute and by the National Institutes of Health, National Institute of General Medical Sciences.


Story Source:

The above story is based on materials provided by Stowers Institute for Medical Research. Note: Materials may be edited for content and length.


Journal Reference:

  1. J. C. Rink, H. T.-K. Vu, A. S. Alvarado. The maintenance and regeneration of the planarian excretory system are regulated by EGFR signaling. Development, 2011; 138 (17): 3769 DOI: 10.1242/dev.066852

Cite This Page:

Stowers Institute for Medical Research. "Flatworms provide new insight into organ regeneration and the evolution of mammalian kidneys." ScienceDaily. ScienceDaily, 12 August 2011. <www.sciencedaily.com/releases/2011/08/110810085544.htm>.
Stowers Institute for Medical Research. (2011, August 12). Flatworms provide new insight into organ regeneration and the evolution of mammalian kidneys. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2011/08/110810085544.htm
Stowers Institute for Medical Research. "Flatworms provide new insight into organ regeneration and the evolution of mammalian kidneys." ScienceDaily. www.sciencedaily.com/releases/2011/08/110810085544.htm (accessed October 25, 2014).

Share This



More Health & Medicine News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) — IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) — A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
WHO: Millions of Ebola Vaccine Doses by 2015

WHO: Millions of Ebola Vaccine Doses by 2015

AP (Oct. 24, 2014) — The World Health Organization said on Friday that millions of doses of two experimental Ebola vaccines could be ready for use in 2015 and five more experimental vaccines would start being tested in March. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Doctor in NYC Quarantined With Ebola

Doctor in NYC Quarantined With Ebola

AP (Oct. 24, 2014) — An emergency room doctor who recently returned to the city after treating Ebola patients in West Africa has tested positive for the virus. He's quarantined in a hospital. (Oct. 24) 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:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

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