CHRONIC CEREBELLAR ALTERATIONS CAUSED BY PERINATAL ASPHYXIA. ESTRADIOL AS A POSSIBLY NEUROPROTECTIVE THERAPY

CAMPANILLE, VERÓNICA; SARACENO, GUSTAVO EZEQUIEL; RIVIÈRE, STÉPHANIE; LOGICA, TAMARA; KOLLIKER FRES, RODOLFO; CAPANI, FRANCISCO; CASTILLA ROCÍO

Congreso; XVI Venezuelan Congress for Microscopy and Microanalysis (XVI CONVEMI).; 2015

Perinatalasphyxia (PA)-induced brain injury is one of the most frequent causes ofmorbidity and mortality in term and preterm neonates, accounting for 23% ofneonatal deaths globally. Following PA, approximately 45% of newborns die and25% have permanent neurological deficits including cerebral palsy, mentalretardation and developmental delay, learning disabilities, eyesight andhearing problems and an impairment in school readiness. The developing brainmay be particularly vulnerable to injury before, at and after birth. The typeand distribution of human brain lesions differ markedly between premature andterm babies, likely as a consequence of the stage of brain maturation andsubsequent regional vulnerability. The cerebellar circuitry appears to beparticularly susceptible, as the cellular makeup and the quantity of inputschange quickly during days and weeks following birth (1). Although different strategieshave been used to treat the consequences of PA, only hypothermia is recommendedas a routine in clinical practice (2). In the last few years, 17b-estradiol has emerged as a potential neuroprotectiveagent against several neuropathological diseases including Parkinson?s,Alzheimer?s, multiple sclerosis and stroke. In recent work, we have shown therepair of chronic neurodegenerative hippocampal modifications in four-month-oldmale Sprague-Dawley rats submitted to severe global PA at the time of birth andinjected 17b-estradiol for 3consecutive days (3). Short-term cerebellar alterations within this PA modelhave been previously reported but whether such alterations remain in adulthoodhas not been conclusively determined yet. For this reason, and given thecrucial cerebellar role in determining connectivity patterns in the brain, theaim of our work was to unveil long-term cerebellum histomorphology following aPA insult and to evaluate the effectiveness of 17b-estradiol as treatment. Morphological and cytologicalneuronal changes and glial reaction in the cerebellar cortex were analyzed atpostnatal day 120 following injury performed at birth. As compared to control,PA animals exhibited: 1) an increase in molecular and granular thickness, both layerspresenting lower cellular density, with no modifications in the total number ofcells, 2) a disarrayed Purkinje cell layer presenting a higher number ofanomalous calbindin-stained cells (Fig 1 A and B) and a reduction in calbindinexpression as evaluated by Western blot, 3) focal swelling and markedfragmentation of microtubule-associated protein 2 (MAP-2) in Purkinje celldendrites and, 4) an increase in glial fibrillary acidic protein (GFAP) expressionevaluated by Western blot and a higher percentage of GFAP-positive reactivearea in Bergmann cells and the granular layer. The 17b-estradiol treatment administered three consecutivedays before euthanasia was unable to reverse the morphological or cytologicalchanges produced by PA (Fig 1 C and D). However, 17b-estradiol increased the Bcl2/Bax ratio and calbindinexpression, both associated to cell survival and possibly effective in longertreatments. In conclusion, we demonstrate that PA produces long-term damage incellular histomorphology in rat cerebellar cortex which could be involved inthe pathogenesis of cognitive deficits observed in both animals and humans. Inaddition, we prove that late administration of 17b-estradiol is ineffective in the treatment ofcerebellar alterations produced by PA at the times analyzed.