Neural Stem Cell Properties of an Astrocyte Subpopulation Sorted by Sedimentation Field-Flow Fractionation

Astrocytes encompass a heterogeneous cell population. Using sedimentation field-flow fractionation (SdFFF) method, different, almost pure, astrocyte subpopulations were isolated. Cells were collected from cortex of newborn rats and sorted by SdFFF to obtain different fractions, which were subjected to protein analysis and characterized by immunocytofluorescence. The behavior of the cells was analyzed in vitro, under culture conditions used for neural stem cells. These culture conditions were also applied to cells derived from an adult cortical tissue after traumatic brain injury (TBI). Finally, the astrocytic neural stem-like cells were transplanted in damaged sciatic nerve. Protein analysis indicated a high expression of glial fibrillary acidic protein (GFAP) and vimentin in fraction F3-derived cells. These cells formed neurospheres when cultured with epidermal growth factor and large colonies in a collagen-containing semi-solid matrix. Neurospheres expressed GFAP and nestin and were able in addition to generate neurons expressing MAP2 and oligodendrocytes expressing Olig2. When transplanted in a damaged nerve, cells of F3-derived neurospheres colonized the damaged area. Finally, after TBI in adult rats, cells able to form neurospheres containing a subpopulation of astrocytes expressing vimentin were obtained. Using the SdFFF method, an astrocyte subpopulation presenting stem cell properties was isolated from a newborn rat cortex and from an injured adult rat cortex. The specific activation of this astrocyte subpopulation may provide a potential therapeutic approach to restore lost neuronal function in injured or diseased brain.