Neurogenesis in adult human brain after hemorrhage and ischemic stroke

Introduction
Adult neurogenesis includes proliferation and differentiation of progenitor cells as well as their migration and maturation. In the adult human brain, two neurogenic regions, the hippocampal dentate gyrus (DG) and the subventricular zone (SVZ) of lateral ventricles, have been identified. In the dentate gyrus, three types of transcriptionally active cells and in the subventricular zone, four types of transcriptionally active cells, including GFAP-positive neural stem cells (NSCs), have been differentiated.

Material and methods
The aim of the study was to identify and compare density of neurogenic cells between two study groups of patients (7 men, 7 women, mean age 70 ± 6.03) with ischemic stroke and with hemorrhage (6 men, 2 women, mean age 64.75 ± 12.23) and the control group of patients (6 men, 2 women, mean age 64 ± 10.95) free of neuropathologic changes who died suddenly within less than 10 min.

Results
In both groups, in the hippocampal dentate gyrus and in the subventricular zone of lateral ventricles, the presence of single GFAP-positive neural stem cells and the transcriptionally active cells labelled with phosphorylated histone H3Ser-10 (p-Histone H3Ser-10)/neural progenitor cells (NPCs), was observed. The quantitative analysis of cells with p-Histone H3Ser-10 expression in the hippocampal DG revealed significant differences between the hemorrhage and control groups (p = 0.001, test t). However, in the SVZ, it showed a statistically significant decrease in the density of transcriptionally active cells in the group of patients with ischemic stroke (p = 0.001, test t). A distinct decrease in the density of transcriptionally active cells, proportional to the length of the patients’ hospitalization, was observed.

Conclusions
Hypoxia belongs to pathomechanic factors responsible for ischemic stroke, which can induce neurogenesis. However, hypoxia along with ischemia and other factors implicated in ischemic stroke, such as the patient’s age or duration of ischemia can have a decisive influence on the decrease in the density of transcriptionally active cells in this pathologic process.