Leukemia inhibitory factor contributes to the self-renewal of neural stem cells in the forebrain. Although the existence of endogenous leukemia inhibitory factor in the brain parenchyma has been controversial, the cerebrospinal fluid is known to be another source of leukemia inhibitory factor. No reports of the measurement of leukemia inhibitory factor concentrations in the cerebrospinal fluid, however, exist. In the present study, we determined the leukemia inhibitory factor concentration in cerebrospinal fluid, amniotic fluid, and sera of embryos and dams in mice by enzyme-linked immunosorbent assay. The leukemia inhibitory factor concentrations were found to be constitutively high in the cerebrospinal fluid from embryonic day 11 to embryonic day 17, with a peak on embryonic day 13 and embryonic day 14. These findings correspond to the timing of cortical neuron production in mouse cerebrum.

Leptin is associated with the maintenance of epidermal growth factor (EGF)-reactive neural lineage cells, including the neural progenitors. One-day treatment with leptin (10, 100, or 1000 ng/ml) followed by EGF treatment increased the number of small-sized and mid-sized colonies compared with the nonleptin treatment. Leptin prevented the inactivation of the phosphatidylinositol 3-kinase (PI3 K) and extracellular signal regulated kinase (ERK) pathways in neurosphere cells cultured in the non-EGF medium. Bromodeoxyuridine (BrdU) incorporation into the neurosphere cells induced by leptin was suppressed by LY294002, a PI3 K inhibitor, but not by U0126, a MEK1/2 inhibitor, which activates ERK1/2, although U0126 decreased phosphorylated extracellular signal regulated kinase levels. These results suggest that leptin maintains the self-renewal ability and EGF reactivity of immature neural lineage cells and the signal is mediated, at least in part, by the PI3 K pathway.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic cytokine that has neurotrophic and neuroprotective functions. However, its function in the mid- to late-gestational fetus remains unclear. We used enzyme-linked immunosorbent assay to analyze GM-CSF levels in cerebrospinal fluid (CSF), serum, and amniotic fluid of mouse fetuses. We also examined GM-CSF and receptor α (GM-CSFRα) levels in the fetal brain, liver, and placenta. GM-CSF peaked between embryonic day (E) 14 and E15 in the CSF. GM-CSF level was higher in the fetal serum than in the dam serum on E13 and decreased thereafter. GM-CSF and GM-CSFRα levels peaked between E13 and E15 in the brain. These results suggest that GM-CSF plays stage- and organ-specific roles in fetal development.