Ischemic damage and subsequent proliferation of oligodendrocytes in hippocampal CA1 region following repeated brief cerebral ischemia.

Changes in oligodendrocytes and astrocytes following repeated brief periods of ischemia were studied in gerbils. The repeated brief periods of cerebral ischemia were produced by occlusion of bilateral common arteries for 3 x 3 min at 1-hour intervals. Oligodendrocytes and astrocytes in hippocampal CA1 regions were examined on 1, 3, 7 and 14 days after ischemia. Seven days after ischemia reperfusion, astrocytes, large pale and small dark oligodendrocytes entered the necrotic pyramidal neuron layer and coexisted with microglia. The necrotic matter of neurons and phagolysosome was observed in cytoplasm of some large pale and small dark oligodendrocytes. Most oligodendrocytes also intermingled with reactive astrocytes. These reactive astrocytes showed glial fibrillary acidic protein-positive reaction. Furthermore, proliferating cell nuclear antigen-positive cells increased markedly 7 days after reperfusion. We conclude that the repeated brief cerebral ischemia caused proliferation of oligodendrocytes and astrocytes, and oligodendrocytes may play a phagocytic role for clearance of necrotic matter of neurons.