Age-related severity of focal ischemia in female rats is associated with impaired astrocyte function

In middle-aged female rats, focal ischemia leads to a larger cortical infarction as compared with younger females. To determine if stroke-induced cytotoxicity in middle-aged females was associated with impaired astrocyte function, astrocytes were harvested and cultured from the ischemic cortex of young and middle-aged female rats. Middle-aged astrocytes cleared significantly less glutamate from media as compared with young female astrocytes. Furthermore, astrocyte-conditioned media from middle-aged female astrocytes induced greater migration of peripheral blood monocyte cells (PBMCs) and expressed higher levels of the chemoattractant macrophage inflammatory protein-1 (MIP-1). Middle-aged astrocytes also induced greater migration of neural progenitor cells (NPCs), however, their ability to promote neuronal differentiation of neural progenitor cells was similar to young astrocytes. In males, where cortical infarct volume is similar in young and middle-aged animals, no age-related impairment was observed in astrocyte function. These studies show that the aging astrocyte may directly contribute to infarct severity by inefficient glutamate clearance and enhanced cytokine production and suggest a cellular target for improved stroke therapy among older females.