Mitochondrial Optic Atrophy (OPA)1 expression regulates the injury response to neonatal hypoxia-ischaemia.
Neonatal hypoxic-ischaemic encephalopathy is a leading cause of mortality and long-term neurodevelopmental impairment, in which mitochondrial dysfunction is central to injury progression, yet the molecular mechanisms linking mitochondrial dynamics to neuropathology remain incompletely defined. We combined analysis of human developmental transcriptomic datasets with in vitro primary astrocyte models and an established neonatal mouse model of hypoxia-ischaemia (postnatal day 9, Rice-Vannucci model) to investigate the role of the mitochondrial fusion protein Optic Atrophy 1 (OPA1). OPA1 expression and processing were assessed by quantitative PCR and western blotting, mitochondrial function by imaging and Seahorse bioenergetic assays, and mitochondrial DNA content by quantitative PCR in both astrocytes and whole-brain tissue following injury. Hypoxia-ischaemia induced rapid proteolytic processing of OPA1 in the neonatal brain and reduced OPA1 expression in astrocytes following oxygen-glucose deprivation. Genetic reduction of OPA1 in astrocytes resulted in mitochondrial fragmentation, impaired maximal respiration and spare respiratory capacity (p<0.05), and increased susceptibility to hypoxic stress (p<0.01). In vitro, OPA1 loss was associated with significant depletion of mitochondrial DNA (p<0.05), and mitochondrial DNA content was similarly reduced in the neonatal mouse brain 24 hours after hypoxia-ischaemia compared with controls (p<0.05). In contrast, OPA1 overexpression preserved mtDNA levels and significantly reduced in vivo brain tissue loss at 7 days after injury (p<0.05), while improving astrocyte survival following metabolic stress (p<0.001). These findings identify loss of mitochondrial DNA as a previously unrecognised component of mitochondrial pathology in neonatal hypoxic-ischaemic brain injury and demonstrate that OPA1 is a key determinant of mitochondrial integrity and bioenergetic resilience. Targeting OPA1-dependent pathways may represent a novel therapeutic strategy to limit brain injury following birth asphyxia.