Aging-related cellular and molecular alterations along the trajectories of the neurogenesis. a) Pseudotime analysis of the neurogenic lineage cells in the TS hippocampus. The points are colored by cell types (top) and age (bottom). The arrows indicate the directions of differentiation trajectories. b) Density plot showing the distribution of neurogenic lineage cells and group along the trajectory. c) Pseudotime analysis showing the expression levels of indicated genes along the trajectory from RGLs to neurons of the TS hippocampus. d) Top, pseudotime analysis of neurogenic lineage cells at 3 states in the TS hippocampus. Cells are colored by the states. Bottom, bar plot showing the proportions of neurogenic lineage state in the hippocampus from infancy, adult, and old groups. e) The line and heatmap showing the expression profiles along the pseudotime of DEGs (q value < 1 × 10−4), which were divided into four clusters (C1 to C4) with the expression pattern and enriched GO terms of the corresponding cluster represented on the right. f) The violin diagram shows the expression levels of the C1 to C4 genes in different cell types. g) Representative microscopic fields and quantification of SOX2/Ki67 double-positive cells in the hippocampal DG from infancy, adult, and old TS. Blue, DAPI. Scale bar: low magnification, 100 μm; high magnification, 10 μm. n = 6 to 8, one-way ANOVA, ***P < 0.001. White rectangular boxes represent the focused areas, and white dashed circles indicate the cell bodies of the cells of interest. Similar outcomes were obtained in three repeated independent experiments. h) Representative microscopic fields and quantification of PROX1/DCX double-positive cells in the DG of the hippocampus from infancy, adult, and aged TS. Blue, DAPI. Scale bar: low magnification, 100 μm; high magnification, 10 μm. n = 4 to 7, one-way ANOVA, **P < 0.01, ***P < 0.001. White rectangular boxes represent the focused areas. Similar outcomes were obtained in three repeated independent experiments. ML, molecular layer; GCL, granule cell layer; SGZ, subgranular zone.
