Evidence for stroke-induced neurogenesis in the human brain

Abstract

Experimental stroke in rodents stimulates neurogenesis and migration of newborn neurons from their sites of origin into ischemic brain regions. We report that in patients with stroke, cells that express markers associated with newborn neurons are present in the ischemic penumbra surrounding cerebral cortical infarcts, where these cells are preferentially localized in the vicinity of blood vessels. These findings suggest that stroke-induced compensatory neurogenesis may occur in the human brain, where it could contribute to postischemic recovery and represent a target for stroke therapy.

Fig. 1.

Proliferative status of cells in the ischemic penumbra of human cerebral cortex after stroke. (a) Nuclei stained for the cell proliferation marker Ki-67 (green) are present in the ischemic penumbra, where TOTO-3 (red) has been used to counterstain all nuclei. (Scale bar, 150 μm.) (Inset) Ki-67-stained nucleus shown at higher magnification. (b) Ki-67 (red) (Upper Left) is colocalized with the cell proliferation marker MCM2 (green) (Upper Right) in the nucleus of a cell in the ischemic penumbra. (Scale bar, 10 μm.) (c) Ki-67 (red) (Upper Left) is colocalized with the cell proliferation marker PCNA (green) (Upper Right) in the nucleus of a cell in the ischemic penumbra. (Scale bar, 5 μm.) (d) Ki-67 (red) (Upper Left) colocalizes with a cell-death marker, the 17- to 20-kDa cleavage product of caspase-3 (green) (Upper Right) in cells with misshapen nuclei (top right corner of each panel and Right Inset), but not in cells with normal-appearing nuclei (bottom left corner of each panel and Left Inset). (Scale bar, 10 μm.) (b–d) Bottom Left and Right panels show DAPI-stained nuclei and merged images, respectively.

Fig. 2.

Neuronal character of cells in the ischemic penumbra of human cerebral cortex after stroke. (a) The early neuronal marker DCX (green) is expressed in the cytoplasm of numerous cells in the ischemic penumbra, where its expression does not overlap with that of the astroglial marker GFAP (red). (Scale bar, 150 μm.) (b) The neuronal marker βIII-tubulin (red) is highly expressed in the ischemic penumbra (center of panel), is less highly expressed in adjacent normal cortex (top of panel), and is absent in the ischemic core (bottom of panel). (Scale bar, 200 μm.) (c) DCX (green) is expressed in the cytoplasm of a cell with Ki-67-positive (red) nucleus. (Scale bar, 5 μm.) (d) βIII-tubulin (red) is expressed in the cytoplasm of a cell with Ki-67-positive (green) nucleus. (Scale bar, 7 μm.) (e) TUC-4 (red) is expressed in the cytoplasm of a cell with Ki-67-positive (green) nucleus. (Scale bar, 5 μm.) (f) ENCAM (red), DCX (green), and TUC-4 (purple) are colocalized; the nucleus is counterstained with DAPI (blue). (Scale bar, 10 μm.) (g) A cell with a Ki-67-stained nucleus (red) and DCX-positive cytoplasm (green) exhibits characteristic migratory morphology, with a leading process and trailing nucleus; nuclei are counterstained with DAPI (blue).

Fig. 3.

Vascular niche for stroke-induced neurogenesis in human cerebral cortex. (a) A section stained for DCX (green), TUC-4 (purple), and nestin (red) and counterstained with DAPI (blue) shows DCX- and TUC-4-positive cells, some with the elongated morphology observed in migrating neurons (Inset), in clusters in the vicinity of a capillary that contains erythrocytes. (Scale bar, 20 μm.) (b) DCX-positive cells (green) are in the vicinity of, but distinct from, von Willebrand factor-positive endothelial cells (red); nuclei are counterstained with DAPI (blue). *, vessel lumen. (Scale bar, 15 μm.) (c) DCX-positive cells (green) are in the vicinity of, but distinct from, α₂-actin-positive vascular smooth muscle cells (red); nuclei are counterstained with DAPI (blue). *, vessel lumen. (Scale bar, 15 μm.)