Reactive proliferation of astrocytes studied by immunohistochemistry for proliferating cell nuclear antigen

Astrocyte proliferation in the stab-wounded cerebral cortex of mice was studied using double immunohistochemistry for proliferating cell nuclear antigen (PCNA) and glial fibrillary acidic protein (GFAP). The number of GFAP-positive astrocytes increased markedly from day 0.5 to day 3 after stab wounding. Some GFAP-positive astrocytes in the immediate vicinity of the wound were found to be positive for PCNA. However, the maximum number of these double positive astrocytes was only 5-6% of the number of GFAP-positive astrocytes. This maximum value was observed on days 2.5 and 3. The present study revealed that astrocytes are able to reactively express PCNA, an intrinsic marker of DNA replication. On the other hand, it is suggested that the proliferation of astrocytes in the wounded cerebral cortex is limited, in contrast with their marked reactive up-regulation of GFAP.