NEURODEGENERATIVE MODIFICATIONS DURING PERINATAL ASPHYXIA: CORRELATIVE LIGHT AND ELECTRON MICROSCOPY STUDIES.

CAPANI FRANCISCO; INÉS HERRERA; LUCAS UDOVIN; TAMARA KOBIEC

Sydney

Congreso; 19th International Microscopy Congress; 2018

Statement of the Problem: Diminish in the oxygen levels prompted short and long-term alterations in synapses and related structures that are related to neuronal dysfunction and death. Perinatalasphyxia (PA) is an obstetric complication produced by an impaired gas exchange that lead to neonatal mortality and is a determinant factor for neurodevelopmental disorders. Since pathophysiologicalmechanisms triggered by PA are not still totally unveiled, we investigated the changes in the cytoskeleton organization in the nervous tissue. Methodology & Theoretical Orientation: For this study,we used a well-established murine model of PA [1]. After one, 2, 4 and 6 months of severe PA (20 min) rats were sacrificed and their brains were analyzed by combining photooxidation, conventionalelectron microscopy, and 3-D reconstruction techniques [1]. Findings: After one month of PA, we found an increase in the F-actin staining in neostriatal and hippocampal dendritic spines together withsome filopodia-likes structures, a typical embryonic type of spines in photooxidated tissue [2] [Fig 1 A). In contrast, after second month of PA, spines were less consistent stained. In addition, weobserved an increment of marker for neuronal and glial dysfunction such as GFAP, neurofilament and MAP-2 [4,5]. These modifications were more striking defined after 4 months of PA [3,4]. After 6months of PA post-synaptic densities (PSDs) in neostriatum were highly modified. Using three-D reconstructions and electron tomography we were able to find clear signs of degeneration in theasphyctic PSDs (Fig 1 B and C) [1] Conclusion & Significance: Therefore, we hypothesize that the cytoskeletal changes induced by PA in the rat CNS could lead to the dramatic modifications insynapse and related structures that trigger neuronal damage. In addition, electron tomography, 3-D reconstruction and photooxidation contributed to dissect critical alterations generated by PA thatare not easily displayed using conventional microscopic techniques. Figure A) Electron micrograph of filopodia F-actin stained in hippocampus PA rat. The magnification of a filopodium allows us to observe its long structure and the parenteral dendrites (arrows). Scale bar: 1 μm. (B) Electron micrographl E-PTA staining in neostriatum. Severe PA post-synaptic density showed a clear increment in the thickness. Scale bar 0.5 μm (C) Three-reconstruction of individual post-synaptic density. After 20 min of PA post-synaptic clear signsof degeneration were observed.References[1] Capani, F., Saraceno, G.E., Boti, V., Aón-Bertolino, L., Madureira de Oliveria, D., Barreto, G., Galeano, P., Giraldez-Alvarez, L.D., Coirini H. (2009): Protein ubiquitination in postsynaptic densities after hypoxia in rat neostriatum isblocked by hypothermia. Exp Neurol. 219, 404-13.[2] Saraceno GE, Guelman LR, Castilla R, Udovin LD, Ellisman MH, Capani F (2016) Consequences of excessive plasticity in the hippocampus induced by perinatal asphyxia. Exp Neurol. 286:116-123.[3] 37. Saraceno GE, R, Barreto GE, Gonzalez J, Kölliker-Frers RA, Capani F (2012) Hippocampal dendritic spines modifications induced by perinatal asphyxia. Neural Plast. 2012:873532[4] 27. Muñiz, J, Romero, J, Holubiec, M, Barreto, G, González, J, Saint-Martin, M, Calvo, E, Carlos Cavicchia, J, Castilla, R, Capani, F. (2014) Neuroprotective effects of hypothermia on synaptic actin cytoskeletal changes inducedby perinatal asphyxia. Brain Res. 14; 1563:81-905] Romero JI, Holubiec MI, Logica Tornatore T, Rivière S, Hanschmann EM, Kölliker-Frers RA, Tau J, Blanco E, Galeano P, Rodríguez de Fonseca F, Lillig CH, Capani F. Neuronal Damage Induced by Perinatal Asphyxia Is Attenuatedby Postinjury Glutaredoxin-2 Administration. Oxidative Medicine and Cellular Longevity Oxid Med Cell Longev 2017:4162465.