Stem Cells in Schistosomes!

Good news everyone! A parasite-related paper was released on Wednesday in Nature that involved those monogamous little blood flukes we call the schistosomes! The paper was titled "Adult somatic stem cells in the human parasite Schistosoma mansoni" and it brought up some interesting new information regarding how these worms live so long.

These worms are well-known for their longevity. S. mansoni has been known to live for years, even decades within their hosts.  These worms live an average of 5-6 years, however there are reports of people becoming infected during childhood and not developing clinical symptoms until adolescence or adulthood. 

A composite image of a scanning electron micrograph
of a pair of male and female Schistosoma mansoni with
the outer tegument (skin) of the male worm "peeled back" (digitally)
to reveal the stem cells (orange) underneath. (Credit: Jim Collins,
Ana Vieira and Phillip Newmark, Howard Hughes Medical Institute
and University of Illinois at Urbana-Champaign)

This newly released study reveals that these worms may be able to achieve such long live spans through the use of stem cells. These findings aren't completely shocking.  These flukes are related to a type of non-parasitic flatworm known as Planaria.  These adorable little turbellarians are often used in zoology labs to demonstrate regeneration to students.  They have a remarkable ability to regenerate from longitutinal and transverse cuts because they house special stem cells known as neoblasts. Stem cells, by definition are able to develop into any type of cell the worm needs...blood cells, muscle cells, etc.  Neoblasts don't just help the Planaria regenerate damaged tissues, they also help to repair tissues that become damaged over time as the worm ages.

Lead researcher Phillip Newmark wondered if maybe schistosomes were living so long because they also had stem cells that repaired damaged tissues to keep the worms young. Following up on his suspicions, he and his team began searching for these cells in schistosomes.

They used fluorescent tagging techniques to find actively dividing cells within the blood flukes, then they isolated the cells and studied them.  Through their observations of these cells, they were able to determine that the cells divided to create two new cells: one that differentiated into another cell type (which varied) and one that was another stem cell.  This is characteristic about what is already known of stem cells.

Here's a quote from Newmark about the research:

The cells we found in the schistosome look remarkably like planarian neoblasts. They aren’t associated with any one organ, but can give rise to multiple cell types. People often wonder why we study the ‘lowly’ planarian, but this work provides an example of how basic biology can lead you, in unanticipated and exciting ways, to findings that are directly relevant to important public health problems.

 
This paper isn't insinuating that these neoblast-like stem cells are the only reason that schistosomes can live for so long, it is merely demonstrating that having these cells plays a role in their longevity. With continued research, it is believed that new treatments for curing people of schistosome infections will be created that target these stem cells for more efficient killing of the parasite.

Isn't biology fascinating?! There's always something new to learn about things that we have spent decades and probably millions...maybe even billions...of dollars researching! Yay for a field that is ever-changing and oh-so-exciting! :D