Evolutionarily, the astrocyte-to-neuron ratio increases from low vertebrates to rodents and to primates (Sherwood et al., 2006). Human cortical astrocytes are larger, structurally more complex and diverse, and propagate calcium waves 4-fold faster than their rodent counterparts (Oberheim et al., 2009). Transplantation of human glia into mice enhances activity-dependent plasticity and learning (Bi et al., 2013). Given the unique biology of human astrocytes, it is critical that improved human-specific cell-based systems be established to enable the study of human astrocyte function in health and disease.
