Effects of elevated magnesium and substrate on neuronal numbers and neurite outgrowth of neural stem/progenitor cells in vitro

Because a potential treatment for brain injuries could be elevating magnesium ions (Mg2+) intracerebrally, we characterized the effects of elevating external Mg2+ in cultures of neonatal murine brain-derived neural stem/progenitor cells (NSCs). Using a crystal violet assay, which avoids interference, of Mg2+ in the assay, it was determined that substrate influenced Mg2+ effects on cell numbers. On uncoated plastic, elevating Mg2+ levels to between 2.5 and 10 mM above basal increased NSC numbers, and at higher concentrations numbers decreased to control or lower levels. Similar biphasic curves were observed with different plating densities, treatment durations and length of tithe in culture. When cells were plated on laminin-coated plastic, NSC numbers were higher even in basal medium and no further effects were observed with Mg2+. NSC differentiation into neurons was not altered by either substrate or Mg2+ supplementation. Some parameters of neurite outgrowth were increased by elevated Mg2+ when NSCs differentiated into neurons on uncoated plastic. Differentiation on laminin resulted in increased neurites even in basal medium and no further effects were seen when Mg2+ was elevated. This system can now be used to study the multiple mechanisms by which Mg2+ influences neuronal biology. Published by Elsevier Ireland Ltd.