Comparative Characteristics of Structural and Functional Changes in the Hippocampal CA₃ Region in White Rats After Acute Ischemia and Brain Injury

The aim of the study was to study pyramidal neurons and astrocytes of the hippocampal CA₃ region in dynamics in white rats after acute ischemia and severe traumatic brain injury.

Material and methods. Acute ischemia was simulated by 20-minute occlusion of the common carotid arteries (CCA), and severe traumatic brain injury (TBI) by a free-falling weight impact. The Nissl staining, hematoxylin and eosin staining, immunohistochemical reactions for NSE, MAP-2, p38, GFAP were used in the study. The proliferative activity of the cells was assessed using the Ki-67 response. The study was carried out on thin (4 μm) serial frontal sections in the animals of the control group (animals without pathological factors, n=5) in 1, 3, 7 and 14 days after the experimental modeling of CCA occlusion (n=20) and TBI (n=20). Morphometric analysis was performed using the ImageJ 1.52s software. The relative area of edema-swelling zones in the neuropil, the number density of pyramidal neurons, the content of dystrophic and necrobiotically altered neurons, the content of neurons with one or more nucleoli, proliferating cells, the density of large trunks of pyramidal neurons dendrites, the total number density and the relative area of giant synaptic terminals in stratum lucidum was detected. The distribution of variation series, the verification of statistical hypotheses, and the construction of graphs were assessed using the Statistica 8.0 software and the R.

Results. Mortality between groups did not differ and did not exceed 7%. In a day after CCA occlusion and TBI, there was a statistically significant increase in the relative volume of edema-swelling, the content of dystrophic and necrobiotically altered neurons, the total number density and the relative area of the terminals decreased, but the total number density of neurons did not change. In 3, 7 and 14 days, the mechanisms of neuroglio- and synaptic plasticity were activated. The content of neurons with two or more nucleoli increased, the total number and content of hypertrophied astrocytes increased, the cytoskeleton of damaged neurons was restored, and the content of interneuronal synapses increased. During the period from 3 to 14 days, the total number density of neurons in CCA occlusion decreased by 16.3%, and in TBI – by 33.7% (p=0.001). Pathological and compensatory-restorative changes were of a diffuse-focal nature and were more pronounced after TBI.

Conclusion. Thus, the same type of focal heterochronous and heteromorphic dystrophic, necrobiotic and compensatory-restorative changes in the nervous tissue were observed after CCA occlusion and TBI in the hippocampal CA₃ region. Structural and functional recovery occurred together with a decrease in the total numerical density of pyramidal neurons and edema-swelling of the nervous tissue. More pronounced dystrophic and necrobiotic changes in TBI were combined with more pronounced compensatory-restorative changes in astrocytes and giant interneuronal synapses of the hippocampal CA₃ region. The revealed changes were considered as the basis for the standard permanent compensatory-restorative reorganization of the nervous tissue of the hippocampus in the postischemic and post-traumatic periods.

1. Borovikov V. Statistica. Iskusstvo analiza dannykh na komp'yutere. 2-oe izd. Sain-Petersburg: Piter; 2003] (in Russian).

2. Lyu BN, Ismailov SB, Lyu MB. The state of cytoskeleton and its links "oxygen-peroxide" effects in some pathologies and apoptosis. Biomeditsinskaya Khimiya. 2008;54(1):58–77] (in Russian).

3. Semchenko VV, Stepanov SS, Bogolepov NN. Sinapticheskaya plastichnost' golovnogo mozga (fundamental'nye i prikladnye aspekty). M.: Direkt-Media; 2014] (in Russian).

4. Stepanov AS. Comparative characteristics of the white rats neocortex, hippocampus and amygdale complex synaptoarchitectonics in norm and after acute ischemia. Journal of Anatomy and Histopathology. 2017 Dec 12;6(4):47–54] (in Russian).

5. Stepanov AS, Akulinin VA, Stepanov SS, Avdeev DB, Gorbunova AV. Neurons Communication in the Hippocampus of Field CA3 of the White Rat Brain after Acute ischemia. General Reanimatology. 2018 Oct 28;14(5):38–49] (in Russian).

6. Stepanov SS, Akulinin VA, Avdeev DB, Stepanov AS, Gorbunova AV. Structural-functional Reorganization of the Nucleolar Apparatus of Neurons of the Neocortex, Archicortex and Basal Ganglia of the Brain of White Rats After a 20-minute Occlusion of the Common Carotid Arteries. Journal of Anatomy and Histopathology. 2019 Jan 11;7(4):67–74] (in Russian).

7. Yashkichev VI. Change of hydration of proteins of the cytoskeleton – mechanism of creation and movement of nerve impulse. Environment and Human: Ecological Studies. 2015;1–2:58–64] (in Russian).

8. Arneson D, Zhang G, Ying Z, Zhuang Y, Byun HR, Ahn IS, et al. Single cell molecular alterations reveal target cells and pathways of concussive brain injury. Nature Communications. 2018 Sep 25;9(1):3894. doi: 10.1038/s41467-018-06222-0

9. Blennow K, Brody DL, Kochanek PM, Levin H, McKee A, Ribbers GM, et al. Traumatic brain injuries. Nature Reviews Disease Primers. 2016 Nov 17;2(1): 16084. doi: 10.1038/nrdp.2016.84

10. Cole JH, Jolly A, de Simoni S, Bourke N, Patel MC, Scott G, et al. Spatial patterns of progressive brain volume loss after moderate-severe traumatic brain injury. Brain. 2018 Jan 4;141(3):822–36. doi: 10.1093/brain/awx354

11. Coronado VG, Xu L, Basavaraju SV, et al. Surveillance for traumatic brain injury-related deaths – United States, 1997–2007. MMWR CDC Surveill Summ. 2011;60:1–32.

12. Grieves RM, Duvelle É, Wood ER, Dudchenko PA. Field repetition and local mapping in the hippocampus and the medial entorhinal cortex. Journal of Neurophysiology. 2017 Oct 1;118(4):2378–88. doi: 10.1152/jn.00933.2016

13. Harris TC, de Rooij R, Kuhl E. The Shrinking Brain: Cerebral Atrophy Following Traumatic Brain Injury. Annals of Biomedical Engineering. 2019;47(9):1941–59. doi: 10.1007/s10439-018-02148-2

14. Hobbiss AF, Ramiro-Cortés Y, Israely I. Homeostatic Plasticity Scales Dendritic Spine Volumes and Changes the Threshold and Specificity of Hebbian Plasticity. iScience. 2018 Oct;8:161–74. doi: 10.1016/j.isci.2018.09.015

15. Leal G, Bramham CR, Duarte CB. BDNF and Hippocampal Synaptic Plasticity. Vitamins and Hormones. 2017;104:153–95. doi: 10.1016/bs.vh.2016.10.004

16. Legéndy CR. On the ‘data stirring’ role of the dentate gyrus of the hippocampus. Reviews in the Neurosciences. 2017 Jul 26;28(6):599–615. doi: 10.1515/revneuro-2016-0080

17. Majdan M, Plancikova D, Brazinova A, Rusnak M, Nieboer D, Feigin V, et al. Epidemiology of traumatic brain injuries in Europe: a cross-sectional analysis. The Lancet Public Health. 2016 Dec;1(2):e76–83. doi: 10.1016/S2468-2667(16)30017-2

18. Moser EI, Moser M-B, McNaughton BL. Spatial representation in the hippocampal formation: a history. Nature Neuroscience. 2017 Nov;20(11):1448–64. doi: 10.1038/nn.4653

19. Ng SY, Lee AYW. Traumatic Brain Injuries: Pathophysiology and Potential Therapeutic Targets. Frontiers in Cellular Neuroscience. 2019 Nov 27;13:528. doi: 10.3389/fncel.2019.00528

20. Palacios EM, Sala-Llonch R, Junque C, Fernandez-Espejo D, Roig T, Tormos JM, et al. Long-term declarative memory deficits in diffuse TBI: Correlations with cortical thickness, white matter integrity and hippocampal volume. Cortex. 2013 Mar;49(3):646–57. doi: 10.1016/j.cortex.2012.02.011

21. Paxinos G, Watson C. The Rat brain in stereotaxic coordinates. 5th ed. San Diego: Elsevier Academic Press; 2005.

22. Raven F, Van der Zee EA, Meerlo P, Havekes R. The role of sleep in regulating structural plasticity and synaptic strength: Implications for memory and cognitive function. Sleep Medicine Reviews. 2018 Jun;39:3–11. doi: 10.1016/j.smrv.2017.05.002

23. Rennert RC, Wali AR, Steinberg JA, Santiago-Dieppa DR, Olson SE, Pannell JS, et al. Epidemiology, Natural History, and Clinical Presentation of Large Vessel Ischemic Stroke. Neurosurgery. 2019 Jun 14;85(suppl_1):S4–8. doi: 10.1093/neuros/nyz042

24. Spitz G, Bigler ED, Abildskov T, Maller JJ, O’Sullivan R, Ponsford JL. Regional cortical volume and cognitive functioning following traumatic brain injury. Brain and Cognition. 2013 Oct;83(1):34–44. doi: 10.1016/j.bandc.2013.06.007

25. Stein TD, Alvarez VE, McKee AC. Concussion in Chronic Traumatic Encephalopathy. Current Pain and Headache Reports. 2015 Aug 11;19(10):47. doi: 10.1007/s11916-015-0522-z

26. van den Bedem H, Kuhl E. Molecular mechanisms of chronic traumatic encephalopathy. Current Opinion in Biomedical Engineering. 2017 Mar;1:23–30. doi: 10.1016/j.cobme.2017.02.003