Title: Novel injury scoring tool
Legend: The freshly harvested whole brain, ipsilateral (IL) and contralateral (CL) hippocampi samples were examined under a microscope and injury scores were assigned from 0 to 6. Hippocampi are scored as 0, if the IL hippocampus has identical tissue consistency and morphology with the CL hippocampus. Hippocampi are scored as 1, if the head of the IL hippocampus (approximately 1/3 of the length of the hippocampus) is slightly opaque compared to the CL hippocampus. Hippocampi are scored as 2, if the opacity in the IL hippocampus extends to the body (approximately 1/2 of the length of the hippocampus) and slight liquefaction in the head of IL hippocampus is present. Hippocampi are scored as 3, if the opacity in the IL hippocampus constitutes 2/3 of the length of the hippocampus and slight liquefaction is observed in the entire IL hippocampus. Hippocampi are scored as 4, if there is opacity and moderate liquefaction in the entire IL hippocampus, and if there is a slight loss of shape due to liquefaction. Hippocampi are scored as 5, if opacity and moderate liquefaction is present in the entire IL hippocampus along with moderate shape loss. Hippocampi are scored as 6, if there is total liquefaction in the IL hippocampus that causes total shape loss. The injury scores were then grouped together based on severity of injury. Injury scores 0 and 1 were assigned as mild, 2 and 3 were assigned as moderate, 4, 5, and 6 were assigned as severe. Sham samples were assigned as having no injury. Whole brain photographs are shown with white arrows denoting cortical infarcts.
Citation: Ozaydin B, Bicki E, Taparli OE, Sheikh TZ, Schmidt DK, Yapici S, Hackett MB, Karahan-Keles N, Eickhoff JC, Corcoran K, Lagoa-Miguel C, Guerrero Gonzalez J, Dean Iii DC, Sousa AMM, Ferrazzano PA, Levine JE, Cengiz P. Novel injury scoring tool for assessing brain injury following neonatal hypoxia-ischemia in mice. Dev Neurosci. 2022 May 25. doi: 10.1159/000525244. Epub ahead of print. PMID: 35613558.
Abstract: The variability of severity in hypoxia ischemia (HI) induced brain injury among research subjects is a major challenge in developmental brain injury research. Our laboratory developed a novel injury scoring tool based on our gross pathological observations during hippocampal extraction. The hippocampi received scores of 0-6 with 0 being no injury and 6 being severe injury post-HI. The hippocampi exposed to sham surgery were grouped as having no injury. We have validated the injury scoring tool with T2-weighted MRI analysis of percent hippocampal/hemispheric tissue loss and cell survival/death markers after exposing the neonatal mice to Vannucci’s rodent model of neonatal HI. In addition, we have isolated hippocampal nuclei and quantified the percent good quality nuclei to provide an example of utilization of our novel injury scoring tool. Our novel injury scores correlated significantly with percent hippocampal and hemispheric tissue loss, cell survival/death markers, and percent good quality nuclei. Caspase-3 and Poly (ADP-ribose) polymerase-1 (PARP1) have been implicated in different cell death pathways in response to neonatal HI. Another gene, sirtuin1 (SIRT1), has been demonstrated to have neuroprotective and anti-apoptotic properties. To assess the correlation between the severity of injury and genes involved in cell survival/death, we analyzed caspase-3, PARP1, and SIRT1 mRNA expressions in hippocampi 3 days post-HI and sham surgery, using RT-qPCR. The ipsilateral (IL) hippocampal caspase-3 and SIRT1 mRNA expressions post-HI were significantly higher than sham IL hippocampi, and positively correlated with the novel injury scores in both males and females. We detected a statistically significant sex difference in IL hippocampal caspase-3 mRNA expression with comparable injury scores between males and females with higher expression in females.
About the Lab: Dr. Pelin Cengiz’s research focuses on finding a novel therapy for neonatal encephalopathy after hypoxia ischemia (HI). She uses the experimental (Vannucci-Rice) mouse model of hypoxia ischemia (HI) to study the sexually differentiated role of neurotrophin signaling in the neonatal hippocampus post-HI. The neurotrophin receptor, tyrosine kinase B (TrkB), plays an important role in neuroprotection and improving the long-term functional recovery following cerebral ischemia by increasing neuronal survival. She has shown that administration of 7,8 dihydroxyflavone (7,8-DHF; potent and selective TrkB agonist) increases TrkB phosphorylation and hippocampal neuronal survival following HI in female, but not in male newborn mice. This female-specific responsiveness to TrkB agonist therapy mimics improved outcomes observed clinically in female newborn humans post-HI. Her studies focus on the cellular mechanisms of the female-specific responsiveness to TrkB agonist and their roles in improving long-term neurological and functional outcome post-HI. An improved understanding of the cellular mechanisms that underlie sex-specific neurotrophin responses will identify new avenues for developing novel therapeutics for neonates and children suffering from brain injury.
Investigator: Pelin Cengiz, MD