Figure 4.

¹⁵N-leucine incorporation in CA1 pyramidal neurons evaluated by NanoSIMS. (A) Overview of the hippocampus showing dense proliferation signals (EdU) in the dentate gyrus. The white square illustrates the EdU signal-free area in the pyramidal layer, analyzed by NanoSIMS. (B,C) Illustration of samples following placebo treatment; (D,E,E’) Illustration of samples following erythropoietin (EPO) treatment; arrows in panel (E’) point to newly generated neuronal cell mass with high¹⁵N/¹⁴N ratio; stars in (E’) denote “control” signal in cytoplasmic regions of older neurons. (F,G) Scatter plots of ¹⁵N/¹⁴N ratios in pyramidal neurons in both treatment groups. (H,I) Coefficient of variation of ¹⁵N/¹⁴N ratios in cytoplasm and nuclei of pyramidal neurons (n = 3 for both groups). All bar graphs are shown as mean ± s.e.m.; **P < 0.01 (unpaired two-tailed t-test). ¹⁵N incorporation appears higher in EPO-treated mice, indicating increased protein synthesis within pyramidal neurons treated with EPO. These observations thus show that EPO may contribute to central nervous system regeneration in adults, which may have behavioral and cognitive implications. Reproduced with permission from Hassouna et al. (2016).