Characteristics of apoptosis during different phases of cell cycle between astrocytes and neurons

Objective To investigate the different characteristics of apoptosis during the different phases of cell cycle between astrocytes and neurons, so as to explore the apoptosis mechanism of the 2 kinds of cells. Methods Ischemia/reperfusion injury was induced by temporary middle cerebral artery occlusion (MCAO). And the brain was taken 3 d after injury. Thymidine analogues such as bromodeoxyuridine (BrdU) was used to incorporate during the S phase of the cell cycle, and the combined visualization of BrdU labeling and Tdt-mediated dUTP-biotin nick end labeling was performed to investigate the apoptosis in the adult rat brain in vivo. Then the apoptosis during the different phases of cell cycle between astrocytes and neurons was detected by flow cytometry (FCM) and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) methods. Results Compared to the normal controls, BrdU or TUNEL positive cells were increased in injury group, and a few of of BrdU and TUNEL double positive cells were found. The most apoptotic neurons and astrocytes were in G0/G1 phase, and the apoptotic neurons were less than astrocytes in G0/G1 phase (P＜0.01), but the apoptotic neurons were more than astrocytes in S phase (P＜0.01). Conclusions Astrocytes and neurons may have the different characteristics of apoptosis during the different phases of cell cycle, which is induced at different check-points. Key words: Astrocytes; Neurons; Cell apoptosis; Cell cycle; Cerebral ischemia