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NG2 proteoglycan-expressing microglia as multipotent neural progenitors in normal and pathologic brains
Akiko Yokoyama1, Aiko Sakamoto, Kenji Kameda
1Department of Molecular and Cellular Physiology, School of Medicine, Ehime University, Toon, Ehime 791-0295, Japan.
Abstract:
Rat primary microglia (MG) acquired a multipotent property to give rise to neuroectodermal cells through two-step culture in 10 and 70% serum-supplemented media for 5 days. Such multipotent MG, called promicroglioblasts (ProMGBs), formed cell aggregates, which generated cells with neuroectodermal phenotypes shortly after their transfer into serum-free medium. As revealed by immunohistochemistry, there were a few MG expressing NG2 chondroitin sulfate proteoglycan (NG2) in the neonatal rat brain. Primary culture from the neonatal brain contained NG2+ MG, which appeared to be the source of NG2+ ProMGB aggregates. The aggregates were MG marker+/NG2+/GFAP+/NCAM+/S-100beta- and had alkaline phosphatase activity. The marked accumulation of NG2+ MG was observed close to stab wounds made in the mature rat brain. The accumulated NG2+ MG in the wound gradually decreased in number, but the cells persisted up to 150 days postlesioning. In addition, GFAP immunoreactivity increased markedly around the wound. The NG2+ MG in the wounds separated with trypsin-EDTA formed NG2+ aggregates in 70% serum-supplemented medium and then transformed into cells with neuroectodermal phenotypes in serum-free medium. Although it is difficult to separate viable neurons from mature brains, cells from stab wounds generated process-bearing beta-tubulin III+ cells in vitro easily. These data suggest that NG2+ MG in normal developing or pathologic brains are involved in the genesis or regeneration of the brain.
Insights
Rat microglia (MG) can become multipotent promicroglioblasts (ProMGBs) and generate neuroectodermal cells. NG2+ MG in developing and injured brains may play a role in brain genesis and regeneration.
Area of Science:
- Neuroscience
- Stem Cell Biology
- Developmental Biology
Background:
- Microglia (MG), the resident immune cells of the brain, are increasingly recognized for roles beyond immunity.
- The potential of microglia to differentiate into other neural cell types remains an area of active investigation.
Purpose of the Study:
- To investigate the multipotent differentiation potential of rat primary microglia.
- To identify specific microglial markers and their role in neurogenesis and brain repair.
Main Methods:
- Primary microglia culture from neonatal rat brains.
- Two-step culture in varying serum concentrations to induce differentiation.
- Immunohistochemistry to identify cell markers (NG2, GFAP, NCAM, S-100beta, beta-tubulin III).
- Analysis of microglia in experimentally induced brain wounds.
Main Results:
- Primary microglia cultured in serum-supplemented media acquired multipotency, forming promicroglioblasts (ProMGBs).
- NG2+ microglia were identified in neonatal brains and accumulated at sites of injury in mature brains.
- ProMGB aggregates generated neuroectodermal cells in vitro, including beta-tubulin III+ cells.
- NG2+ microglia persisted in brain wounds for up to 150 days post-lesioning.
Conclusions:
- Rat primary microglia possess multipotent properties, differentiating into neuroectodermal cells.
- NG2+ microglia are present in normal developing and injured brains.
- These findings suggest a role for NG2+ microglia in brain development and repair processes.
