Effects of olfactory ensheathing cells on hydrogen peroxide-induced apoptosis in cultured dorsal root ganglion neurons

Background Olfactory ensheathing cells (OECs) can promote many kinds of neuron growth and axonal extension. The aim of the study was to investigate the effects of co-culturing with OECs on neuron apoptosis in vitro. Methods Apoptosis was induced by treatment of cultured dorsal root ganglion neurons with 1 mmol/L hydrogen peroxide (H2O2). Cells were randomly arranged into the following treatment groups. In group 1, OECs at different density (10(4)/ml to 8x10(5)/ml) were added immediately after H2O2 treatment and cells were co-cultured for 24 hours. In group 2, OECs were added at different time points (0, 4, 8, 12 and 24 hours) after H2O2 treatment. Apoptotic cell death was determined by Hoechst 33258 staining and flow cytometry (FCM). Cell viability was determined by using methyl thiazoleterazolium (MTT) assays. Results The results showed in the Hoechest 33258 staining, FCM and MTT that OECs have both the density-dependent protection and time-dependent protection on neuron apoptosis. The apoptosis decreased and the dorsal root ganglion neuron viability increased, when the density of OECs was increased in co-culture groups. But further increasing OEC density above 2x10(5)/ml (i.e. 8x10(5)/ml) failed to exert additional protection. As the interval between adding H2O2 and adding OECs was increased, the amounts of apoptosis cells were also increased. When OECs were added 24 hours after H2O2, no significant protection was observed. Conclusion These results indicated that OECs could protect dorsal root ganglion neurons from apoptosis induced by H2O2 in a density- and time-dependent manner.