Planaria are Proving to be an Informative Animal Model System

With amazing regenerative capabilities, the freshwater flatworm planaria is a favorite animal model system in the Sánchez Alvarado Lab at the Stowers Institute. Scientists use it to study the molecular and cellular mechanisms that drive regeneration and restoration of body parts. New studies from the Sánchez Alvarado Lab utilizing these curious creatures highlight two projects with intriguing findings.

Shifts in the Microbiome Impact Tissue Repair and Regeneration

Shifts in the balance of the human microbiome—the microbial communities that call our bodies home—underlie persistent inflammatory disorders, chronic nonhealing wounds, and scar formation. In a recently published paper, Stowers scientists in the Sánchez Alvarado Lab explore the interplay between the microbiome, host immunity, tissue repair, and regeneration in planaria.

Postdoctoral Research Associate Chris Arnold, PhD, and collaborators find that ailing flatworms experience a dramatic expansion of pathogenic Proteobacteria that closely mirrors changes associated with human ailments. This bacterial infection stimulated the flatworms’ immune response, impeding their regeneration capabilities. The study provides a valuable animal model for understanding host-microbiome interactions and for designing therapies that may enhance healing in humans.

“This is the first animal model to link pathological shifts in endogenous bacteria with the inhibition of regeneration,” says Sánchez Alvarado. “We know that some kinds of bacteria are critical to our health, and that other kinds of bacteria can make it very difficult for us to recover from illness. Now we can study how the changing nature of the microbiome—and the way the immune system responds to those changes—impacts the natural execution of regenerative processes.”

The study was published July 21, 2016, in the journal eLife.

A Key Molecular Signal Shapes Regeneration in Planarian Stem Cells

Like a magician, planaria can survive decapitation or even being cut into many pieces. But the flatworm does not need to rely on trickery.

Its remarkable ability to fully regenerate from tiny remnants of tissue is due to a special population of adult stem cells known as neoblasts. In recently published work, Stowers scientists explore the precise mechanisms shaping the population dynamics of neoblasts.

Postdoctoral Research Associate Kai Lei, PhD, and collaborators have discovered that a molecule called EGFR-3 is part of a cascade of signals necessary for neoblasts to regenerate, and might control the way these cells divide and differentiate in response to otherwise lethal doses of radiation.

The finding has important implications for advancing regenerative medicine and for developing more effective cancer therapies. Sánchez Alvarado explains, “Anything that perturbs our body—aging, injury, even a spicy meal—can affect our stem cell functions. If we understand better how planarians regulate the population dynamics of their stem cells, it may provide a clue for addressing our own pathologies.”

These results were published online August 11, 2016, in the journal Developmental Cell.