Background: Astrocytes are not only structural cells but also play a pivotal role in neurogenesis and neuroprotection by secreting a variety of neurotrophic factors that support neuronal survival, growth, and repair. This study investigates the time-dependent responses of primary rat cortical astrocytes to oxygen–glucose deprivation (OGD) and evaluates the neuroprotective potential of astrocyte-conditioned medium (ACM). Methods: Primary rat cortical astrocytes and neurons were obtained from postnatal Sprague Dawley rat pups (P1–3) and embryos (E17–18), respectively. Astrocytes exposed to 6, 24, and 48 h of OGD (0.3% O2) were assessed for viability, metabolic function, hypoxia-inducible factor 1 and its downstream genes expression. Results: While 6 h OGD upregulated protective genes such as Vegf, Glut1, and Pfkfb3 without cell loss, prolonged OGD, e.g., 24 or 48 h, led to significant astrocyte death and stress responses, including elevated LDH release, reduced mitochondrial activity, and increased expression of pro-apoptotic marker Bnip3. ACM from 6 h OGD-treated astrocytes significantly enhanced neuronal survival following 6 h OGD and 24 h reperfusion, preserving dendritic architecture, improving mitochondrial function, and reducing cell death. This protective effect was not observed with ACM from 24 h OGD astrocytes. Furthermore, 6 h OGD-ACM induced autophagy in neurons, as indicated by elevated LC3b-II and decreased p62 levels, suggesting autophagy as a key mechanism in ACM-mediated neuroprotection. Conclusions: These findings demonstrate that astrocytes exhibit adaptive, time-sensitive responses to ischemic stress and secrete soluble factors that can confer neuroprotection. This study highlights the therapeutic potential of targeting astrocyte-mediated signalling pathways to enhance neuronal survival following ischemic stroke.
Singh et al. (Thu,) studied this question.