Mice that received transplants of human glial progenitor cells learned much more quickly than normal mice, according to a study published today (March 7) in Cell Stem Cell. The findings support the theory that glial cells made a significant contribution to the evolution of our own enhanced cognitive abilities.
“This work is very exciting and surprising because it demonstrates that there may be something special about human glial progenitor cells that contribute to the amazing complexity and computational abilities of the human brain,” said Robert Malenka, a neuroscientist at Stanford University who was not involved in the study, in an email to The Scientist.
For many years, glia cells, non-neuronal cells present in the same numbers as neurons in the brain, were thought to play only a supporting role, providing structure, insulation, and nutrients for neurons. But in the past 20 years it has become clear that glia also participate in the transmission of electrical signals. Specifically, astrocytes—a type of glial cell with thousands of tendrils that reach and encase synapses—can modulate signals passing between neurons and affect the strength of those connections over time.
Recent studies have also demonstrated that human astrocytes are very different from those found in mouse and rat brains, on which most previous studies of astrocyte physiology were based. Human astrocytes are more numerous, larger, and more complex, and they are capable of far more rapid signaling responses than rodent astrocytes.
Together, these results suggest that astrocytes may have been critical to the evolution of enhanced neural processing in humans. Having already transplanted human glial progenitor cells (GPCs) to restore myelination in myelin-deficient mice, Steven Goldman of University of Rochester Medical Center in New York and colleagues realized that they could repeat the trick in normal mice to assess the contribution of human-specific astrocytes to synaptic plasticity and learning.