Effects of inflammatory cytokines and minocycline on cultured neural stem cells

Introduction: Manipulating endogenous neural stem cells (NSCs) in the adult brain has emerged as an experimental concept, aimed at enhancing the brain’s regenerative capacity after insults such as stroke. Neuroinflammatory processes occuring after stroke are mediated by pro-inflammatory cytokines such as TNF-alpha, interleukin–1ß (IL–1ß) and IL–6; however, their effects on NSCs are unknown to date. The tetracycline minocycline has neuroprotective effects in stroke, but – likewise – its effects on NSCs are unclear to date. Method: NSCs were dissected from fetal rat cortex (E13.5) and grown as monolayer cultures. To study the effects of pharmacological agents on NSCs, cultures were treated with various concentrations or combinations of TNF-alpha, IL–1ß, IL–6, and minocycline, and NSC numbers were assessed over time using a photometric assay (MTT). Furthermore, the effects of those drugs on NSC proliferation and differentiation potential were examined using immunocytochemical methods. Results: 10µM and 50µM of minocycline significantly increased NSC numbers compared to control conditions. This effect could not be attributed to an increase in NSC proliferation, thus indicating a positive effect of minocycline on cell survival. Minocycline alone did not affect the differentiation potential of NSCs. A cocktail of TNF-alpha, IL–1ß and IL–6 neither affected NSC numbers nor their proliferative activity. However, pro-inflammatory cytokines accelerated the differentiation of NSCs, promoting a glial fate. This effect was partly inhibited by co-treatment with minocycline. Conclusion: Our data suggest that minocycline positively affects NSC survival and promotes their tri-potential, undifferentiated state, while pro-inflammatory cytokines typically upregulated after stroke such as TNF-alpha, IL–1ß, and IL–6 accelerate NSC differentiation toward a glial fate. These results should help to establish novel (combinatory) treatments targeting the endogenous NSC niche in stroke.