These two broad categories of proliferative border-forming astrocytes or non-proliferative hypertrophic reactive astrocytes should not be considered an exhaustive characterization of potential reactive astrocyte subtypes. As available information grows, additional subtypes, or subdivisions of these two are likely to emerge. It is recommended that classifying different subtypes be based on composite pictures that take into account multiple forms of information about differences in astrocyte morphology, cell lineage, proliferative state, molecular expression, cellular interactions and functions. Defining such differences is an important goal for future research. This working model and framework (Key Figure, Figure 2) is intended as a beginning categorization to be expanded upon.
