Manganese-enhanced MRI detection of neuro degeneration in neonatal hypoxic-ischemic cerebral injury

In this study, we investigated the Mn-enhanced MRI (MEMRI) for detecting neurodegenerative processes in neonatal hypoxic-ischemic (H-I) cerebral injury. Seven-day-old rats were induced with H-I injury, and scanned for T-1-weighted image (T1WI) and T-2-weighted image (T2WI) with and without systemic MnCl2 administration. Serial histological analysis was performed for Mn-superoxide dismutase (Mn-SOD) and glutamine synthetase (GS), which are Mn-binding enzymes against the oxidative stress and glutamate excitotoxicity in neurodegeneration. In the acute phase (first 2 days), the ipsilateral lesion exhibited no Mn enhancement in T(1)WIs, with histology showing no Mn-SOD and CIS production. In the mid-phase (from day 3), Mn enhancement was found in the cortex, basal ganglia, and hippocampus, correlating with local Mn-SOD and GS increase. In the late phase, the enhancement became more localized to the pericyst basal ganglia and cortex, and then gradually diminished. In T(2)WIs, a signal decrease was observed from day 3 in the corresponding regions. Hypointense voids gradually formed in the late phase, correlating with the local iron accumulation. H-I rats without Mn2+ administration exhibited similar but weak changes in T(1)WIs and T(2)WIs from days 14 and 7, respectively. These results indicate that Mn2+ may be a useful in vivo probe for monitoring Mn-SOD and GS enzymatic activities.