Regeneration, Repair, and Developmental NeuroscienceResearch PaperBrain injury activates microglia that induce neural stem cell proliferation ex vivo and promote differentiation of neurosphere-derived cells into neurons and oligodendrocytes
Research Highlights
▶Neurospheres are larger and more numerous when derived and cultured from an injured brain, SVZ, (ischemic stroke and excitotoxic brain injury). ▶A proliferative population of microglial cells are retrieved from injured neurosphere cultures that exert a robust proliferative effect on neurospheres. ▶Microglial cultures from injured brains can be used as an ex vivo system to study proliferation of neural stem/progenitor cells.
Section snippets
Animals
We used male Sprague–Dawley rats (B&K Stockholm, Sweden), aged 10–12 weeks at the start of the experiment. All experiments were approved by the Malmö-Lund Ethical Committee. Animals had free access to food and water and were housed under a 12-h light/12-h dark cycle. We used a minimal number of animals and efforts were done to avoid suffering.
Experimental model of stroke
We induced experimental stroke, focal brain ischemia, by transient middle cerebral artery occlusion (tMCAO) using an established protocol (Memezawa et
Distinct microgliosis in the striatum of rats at one and four weeks following brain injury
To develop an ex vivo system to study the effect of microglial cells on NSPCs, we activated microglial cells by inducing experimental stroke (tMCAO) and excitotoxic brain injury in rats. We first examined striatal microgliosis following brain injury using immunohistochemistry for the microglial marker CD11b at 1 and 4 weeks post-injury. At both time points, the microglial hyperplasia appeared identical at the cellular level with hypertrophic microglial cells that exhibited characteristic bushy
Discussion
We have developed an ex vivo model to study activated microglia-induced proliferation of NSPCs following brain injury in vivo. We found that microglia activated because of brain injury influenced NSPC proliferation. Specifically, we demonstrated an increase in cell proliferation in neurospheres generated from NSPCs isolated from the ipsilateral SVZ tissue following both ischemic stroke and excitotoxin-induced lesion. Enhanced neurogenesis has been suggested to occur in stroke patients (Jin et
Conclusion
We have generated an ex vivo model to study the response of NSPCs to microglial cells obtained from injured brains. Our data imply that microglial cells present in acutely damaged SVZ/striatum release factors that initially promote proliferation. We also show that NSPCs derived from an injured brain differentiate to a higher extent into neurons and oligodendrocytes. These results suggest that a microglial change might underlie the increased cell proliferation observed in the SVZ and the
Acknowledgments
This work was supported by the Swedish Research Council (including NeuroFortis, Strong Research Environment on Neurodegeneration and Brain Repair), EU 6th framework program PROMEMORIA, Crafoord Foundation, Gyllenstiernska Krapperup foundation, Royal Physiographic Society, Swedish Stroke Association, Bergvall Foundation, Kock Foundation, Lars Hierta Foundation, Tore Nilsson Foundation and Segerfalk Foundation. We also thank C. Sjölund and B. Haraldsson for providing technical assistance and
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