While many researchers work with animal models like mice, Christopher Arnold, assistant professor in the Department of Biology at the Eberly College of Arts and Sciences studies planarians. These unique creatures, also known as flatworms, have regenerative abilities that make them ideal subjects for investigating the basis of animal regeneration.
I wanted to better understand how stem cells could be used to repair tissues and sought out an animal capable of regenerating lost or damaged body parts. I found the work of Dr. Alejandro Sánchez Alvarado and became fascinated by his studies on the highly regenerative invertebrate flatworm, the planaria Schmidtea mediterranea.
Working with planarians is also a relief on Arnold’s system – he’s allergic to mice.
Arnold grew up in San Diego and got a bachelor’s in molecular biology from University of California San Diego. He got his first research experience in the Wasserman Lab in Massachusetts, studying fly immunity. There, he discovered a love for biological lab experiments and went on to obtain his doctorate from Stanford University in immunology.
Q: Your research took an interesting turn as a graduate student.
A: I joined the [Stanford] Chen lab, where I studied how self-renewal was regulated in embryonic and adult stem cells. My primary animal model was mice, but during my graduate studies, I developed a severe mouse allergy. To pursue my interests in stem cell biology, I needed to find a new (and less furry) animal model. I wanted to better understand how stem cells could be used to repair tissues and sought out an animal capable of regenerating lost or damaged body parts. I found the work of Dr. Alejandro Sánchez Alvarado and became fascinated by his studies on the highly regenerative invertebrate flatworm, the planaria Schmidtea mediterranea. For my postdoctoral work, I joined his laboratory at the Stowers Institute in Kansas City, MO and studied the molecular underpinnings of the planarians’ exceptional regenerative capabilities.
Q: What’s so cool about planarians, anyway?
A: Planarians are truly masters of regeneration. If you cut a piece of tissue from a planaria, it will regrow what was lost in less than a week. At the same time, that small piece of tissue will regenerate into an entirely new worm.
I first studied planarian regeneration in the context of the immune response. To do this effectively, I optimized how to culture the animals to minimize background levels of pathogenic bacteria. Unexpectedly, this optimization unlocked a fascinating yet poorly understood aspect of planarian biology, asexual reproduction. Planaria are so good at regeneration that they can make more copies of themselves by tearing off small pieces of their tissue that go on to regenerate into clones of the parent animal. Typically, this behavior is sporadic in the lab, but I discovered a way to induce it, paving a way to better understand this natural regenerative process. Plus, I have three kids and the concept of an animal that rips itself into pieces for the sake of its offspring resonates with me as a parent.
What I love most about planaria, regeneration, and asexual reproduction is all the new biology that is just waiting to be uncovered. Our hope is that this eccentric little worm can reveal unknown unknowns underlying stem cell biology, behavioral regulation, growth control and more.
Q: What kind of research are you hoping to focus on at Eberly?
A: My research group aims to better understand how animals grow and regenerate through the study of asexual reproduction in planaria. We are currently interested in questions such as how growth is regulated in an animal that can perpetually regrow all of its tissues, which genes underlie the ability of an animal to asexually reproduce, and how regeneration proceeds in different contexts of tissue loss.
Q: Why are planaria a good fit for students?
A: I think our work tackles exciting questions that are grounded in fundamental biology. Planaria are really neat organisms with extreme regeneration and a seemingly limitless lifespan. I look forward to being able to share this incredible animal with WVU students and the other young students in the greater community in West Virginia. Additionally, planaria have a lot of accessible biology and are particularly suited for students just getting started in laboratory research. I hope that our work on fundamental questions like how animals grow and regrow their tissues can provide a launching pad for the scientific careers of many young students in West Virginia and beyond.
Q: Do you have any creatures on the home front?
A: My family and I have an aquarium of guppies for pets. We thought we had purchased all females but one of them turned out to be male. Guppies breed like crazy so our starting population of 6 fish gave rise to multiple generations that have probably accumulated into the 100s of fish by this point. While it is kind of a hassle to maintain the tank and figure out what to do with all the extra fish, it is a great genetic experiment for my kids. You can see traits like fin shape and pigmentation patterns get passed on to the next generation as they breed. Once the tank gets too populated, we let the kids pick a few of their favorites and donate the rest to the pet store. And you can be sure they always include both males and females in their picks so we can go through this process all over again.
Written by Laura Roberts