Background: It has been demonstrated that cerebral ischemia induces astrocyte reactivity, and subsequent glial scar formation inhibits axonal regeneration during the recovery phase. Investigating the mechanism of glial scar formation will facilitate the development of strategies to improve axonal regeneration. However, an in vitro model of ischemia-induced glial scar has not yet been systematically established.
Methodology and principal findings: In the present study, we at the first time found that oxygen-glucose deprivation (OGD) in vitro can induce rat cortical astrocytes to present characteristics of glial scar. After OGD for 6 h, astrocytes showed a remarkable proliferation following 24 h reperfusion, evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and BrdU immunocytochemistry. Meanwhile, the expression of glial fibrillary acidic protein significantly increased, so did the expression of neurocan, which is a hallmark of the glial scar. In further experiments, neurons were co-cultured with astrocytes, which had been exposed to OGD, and then the immunostaining of class III β-tubulin was carried out to assess the neurite growth. When the co-culture was performed at 48 h reperfusion of astrocytes, the neurite growth was obviously inhibited, and this inhibition could be reversed by chondroitinase ABC, which digests glycosaminoglycan chains on CSPGs, including neurocan. However, the processes of neurons were elongated, when the co-culture was performed immediately after OGD.
Conclusions and significance: Our results indicated that after conditioned OGD the astrocytes presented the characteristics of the glial scar, which are also comparable to the astrocytes in acute and chronic phases after cerebral ischemia in vivo. Therefore, the present system may be used as an in vitro model to explore the mechanisms underlying glial scar formation and the treatments to improve axonal regeneration after cerebral ischemia.