Presented at the Neonatal Society 2018 Spring Meeting.
Shipley L, Bloor I, Sharkey D
Academic Child Health, School of Medicine, University of Nottingham
Background: Neonatal ambulance transportation (NAT) is associated with intraventricular haemorrhage (IVH) (1) and exposes preterm infants to excessive whole body vibration (WBV) (2), often at a time when most at risk of IVH. Animal models of chronic WBV develop neuronal injury, glial cell enlargement and proliferation. Hypothesis: WBV experienced during NAT contributes to neuronal injury. Aim: evaluate the effects of a single, short term WBV exposure, as experienced during typical NAT, on the developing brain using a newly developed rodent model.
Methods: Postnatal day 7 and 21 rats (equivalent to 32 week and post-term human neuronal development stages) were randomly divided into control (C) and vibration (V) groups. V groups were exposed to 2m/s2 of WBV for 90 minutes2. Animals were euthanised after 24 hours with brain and serum samples taken for evaluation. Blinded histological quantification of the brain tissue for neuronal oedema, glial cell area and apoptosis (TUNEL staining) was performed. Serum corticosterone was measured using ELISA. Data were analysed using Mann-Whitney. The study was compliant with the Animal Act 1986.
Results: Day 7 V group had significantly more neuronal oedema, glial cells and apoptotic cells compared to Cs. Day 21 V group did not show a significant increase in neuronal oedema but did show an increase in glial and apoptotic cells compared to Cs. Overall, day 7 groups had a greater change from Cs compared to at day 21. However, only day 21 V group demonstrated a stress response with a significant increase in corticosterone.
Data are Median (IQR), * = significant p<0.05 C vs V; ** = significant p<0.01 C vs V
Conclusion: This new animal model of NAT WBV has shown the immature brain is more susceptible to the effects of short term WBV. The microscopic injury sustained could potentially be a consequence of direct mechanical injury or a poor stress response and adaptation due to an immature hypothalamic-pituitary axis. This insult could impact on long-term neurodevelopment in high-risk transported infants even in the absence of significant IVH.
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1. Mohamed et al, ADC FN 2010 95:F403–F407
2. Blaxter et al, Proc Inst Mech Eng H. 2017 231(2):99-113