Laboratory Investigation The Science and Ethics of Stem Cell Research Plenty of Planaria Laboratory Investigation

What are Planaria? Freshwater flatworms (phylum: Platyhelminthes) Live in freshwater under leaves and stones Avoid light (“negative phototaxis”) Free living – not parasites Carnivores – eat decaying meat, insects and larvae (egg yolks or liver in the lab) 1-20 mm in size Long lived Use sexual or asexual reproduction This picture has been released it into the public domain.

Overview of Brown Planaria Dugesia tigrina

Planaria are complex organisms Gastrovascular System

Nervous System

Reproductive System

Excretory/Osmoregulatory System

Why study Planaria to learn about stem cells? Planaria have an amazing ability to regenerate parts of themselves Planaria regeneration is a great model for demonstrating stem cell function and complexity of tissue regeneration They can grow easily in the lab 1/279th

Neoblast = Planaria Stem Cell 20-30% of all the cells in a planaria are Neoblasts. Neoblasts divide by mitosis and can make more of themselves. They are the only dividing cells in planaria. When a planaria is wounded, neoblasts migrate to the site and begin dividing Neoblasts can become ANY cell the planaria needs—nerve cells, flame cells, reproductive cells… Ann. Rev. Cell. Dev. Biol. 20:725-757, 2004

Three types of planaria with their neoblasts labeled with BrdU BrdU (bromodeoxyuridine) is substituted for thymine during DNA replication. Only dividing cells—in this case the neoblasts—will show detectible amounts of BrdU. A. Phagocata sp. B. Girardia dorotocephala C. Schmidtea mediterranea Dugesia sp. (Dev. Biol 220: 142-153, 2000)

Neoblasts and Stem Cells are Totipotent “Totipotent” Stem Cell Blood Nerve Skin They can become any cell type in the body In Humans: Totipotent cells are limited to early embryonic division In Planaria: Neoblasts are always present

Regeneration requires… turning on the right genes at the right time in the cells that come from the dividing stem cells (neoblast).

Care and Feeding of Planaria The water is very important! Fresh water from a pond, stream or lake is best; spring water is adequate Keep cultures in a cool, dark place Feed planaria at least once a week Change the water twice a week, especially after feeding After cutting them, the cultures should not be fed

Student Laboratory Investigation Each team will receive 3 planaria: Experimental Planaria #1 Every team will cut this into half, separating the anterior from the posterior halves. Experimental Planaria #2 This will be cut in a manner determined by your team. Control Planaria This will not be cut. Used with permission from UC Museum of Paleontology

Plenty of Planaria

Planaria Regeneration, Days 1 - 14 Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley

Slide courtesy of Dr. Sánchez Alvarado and Dr. Kyle Gurley