Objective: To investigate the proliferation and differentiation of neural stem cells after cerebral infarction(CI) in adult rats.
Methods: CI animal model was made by ligating the common carotid artery and external carotid artery and inserting a piece of nylon thread into the internal carotid artery among 100 male Wistar rats. Then the rats were randomly divided into 5 groups: group of I day after brain infarction (n = 20), group of 3 days after brain infarction (n = 20), group of 7 days after brain infarction (n = 20), group of 14 days after brain infarction (n = 20), and group of 28 days after brain infarction (n = 20). Twelve rats undergoing sham operation with a piece of nylon thread inserted only into the common carotid artery were used as controls. The rats were killed at different time points and their brains were taken out. The expression of bromodeoxyuridine (BrdU) and Musashil (both used to mark the dividing neural stem cells), and of glial fibrillary acidic protein (GFAP) and neuronal nuclear antigen (NeuN) (both used to mark the differentiating neural stem cells) were determined by immunohistochemistry and immunofluorescence staining.
Results: In the normal brain tissues, only a small amount of BrdU(+) cells were found in the hippocampus. One day after CI the number of BrdU(+) cells began to increase in the hippocampus at the CI side (P < 0.05), peaked 7 days after CI with a number 6 times that at the normal side, began to decrease 14 days after, and almost reached normal 28 days after. The number of BrdU(+)/Musashil(+) cells began to increase 1 day after CI (P < 0.05), peaked 7 days after, began to decrease 14 days after, and almost reached normal 28 days after. The number of BrdU(+)/GFAP(+) cells at the CI side remained almost unchanged after CI. The number of BrdU(+)/NeuN(+) cells began to increase 14 days after CI (P < 0.05) and peaked 38 days after.
Conclusion: Cerebral infarction stimulates the proliferation of inherent neural stem cells and most proliferated neural stem cells differentiate into neurons.