title: The late phase of post-stroke neurorepair in aged rats is reflected by MRI-based measures.
abstract: Non-invasive criteria determining the progress of brain healing are especially important in aging, providing a case-specific therapeutic strategy in populations with dysregulated neurorepair mechanisms. We hypothesized that temporal evolution of magnetic resonance imaging (MRI) of T2 tissue relaxation values correlate with neurological severity scores (NS), and provide a robust indicator of healing in the aging brain after stroke. Pre-treatment of aged rats with brain-only proton irradiation was undertaken to pre-condition the inflammatory system. Irradiation was performed 10days prior to right middle cerebral artery occlusion (MCAO) for 50min (MCAO+Rad). Control rats included naïve (no ischemia, no radiation), irradiated-only (Rad), irradiated ischemic, or ischemic-only (MCAO). MRI and NS were obtained at 3, 14 and 28days post-stroke. At 28days post-stroke, immunofluorescence for visualizing blood vessels (Von Willebrand factor; vWF), neurons (neuronal nuclear antigen; NeuN), astrocytes (glial fibrillary acidic protein; GFAP), activated microglia/macrophages (ionized calcium-binding adapter molecule 1, Iba1), T-lymphocytes (CD3), phagocytes (ED1) and apoptotic cells (caspase-3) was assessed. We found a positive T2-NS correlation in irradiated, ischemic rats that corresponded to late-stage brain recovery. Late-stage brain recovery was characterized by improved neovascularization, formation of glio-vascular complexes (visualized by GFAP/vWF) and enhanced neuronal viability (by NeuN/caspase-3) in the peri-lesional zone. The immune response plateaued at the late stage of repair as evidenced by significantly decreased expression (41.7%) and distribution of phagocytes (phagocytic rim decreased 44.6%). We also found reduced infiltration of T-lymphocytes (CD3) in the brain and normalization of blood lymphocytes. The observed T2-NS correlations may provide a simple MRI-based criterion for recognition of regenerative brain transformation in aged patients following stroke. Selective activation of innate immunity and accelerated transition from pro-inflammatory to pro-healing macrophage phenotypes induced by localized brain irradiation is a potential mechanism for enhancing repair ability in the elderly.
authors.affiliation: Pediatric Research Department, Loma Linda University, Coleman Pavilion, Room A-1120, 11175 Campus Street, Loma Linda, CA 92354, USA; Department of Anesthesiology, Krasnoyarsk State Medical University, Krasnoyarsk, Russia. Electronic address: elenatitovakrsk@gmail.com.
authors.forename: E M
authors.initials: EM
authors.lastname: Titova
authors.affiliation: Pediatric Research Department, Loma Linda University, Coleman Pavilion, Room A-1120, 11175 Campus Street, Loma Linda, CA 92354, USA. Electronic address: nghosh@llu.edu.
authors.forename: N
authors.initials: N
authors.lastname: Ghosh
authors.affiliation: Pediatric Research Department, Loma Linda University, Coleman Pavilion, Room A-1120, 11175 Campus Street, Loma Linda, CA 92354, USA. Electronic address: zvala001@gmail.com.
authors.forename: Z G
authors.initials: ZG
authors.lastname: Valadez
authors.affiliation: Physiology & Pharmacology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA. Electronic address: johnzhang3910@yahoo.com.
authors.forename: J H
authors.initials: JH
authors.lastname: Zhang
authors.affiliation: Department of Pathology and Human Anatomy, Loma Linda School of Medicine, Loma Linda University, Loma Linda, USA. Electronic address: dbellinger@llu.edu.
authors.forename: D L
authors.initials: DL
authors.lastname: Bellinger
authors.affiliation: Pediatric Research Department, Loma Linda University, Coleman Pavilion, Room A-1120, 11175 Campus Street, Loma Linda, CA 92354, USA; Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, CA, USA; Division of Interdisciplinary Studies, School of Behavioral Health, Loma Linda University, Loma Linda, CA, USA. Electronic address: aobenaus@llu.edu.
authors.forename: A
authors.initials: A
authors.lastname: Obenaus
mesh_terms: D000375:Aging; D000818:Animals; D017252:CD3 Complex / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D004195:Disease Models, Animal; D053331:Ectodysplasins / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D020244:Infarction, Middle Cerebral Artery / Q000175:diagnosis* / Q000532:radiotherapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008840:Microfilament Proteins / Q000378:metabolism; D009460:Neurologic Examination; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration / Q000502:physiology*; D013997:Time Factors; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: C100745:Aif1 protein, rat; D017252:CD3 Complex; D002135:Calcium-Binding Proteins; D053331:Ectodysplasins; D005904:Glial Fibrillary Acidic Protein; D008840:Microfilament Proteins; D014841:von Willebrand Factor; D053148:Caspase 3
keywords: brain repair; cerebral ischemia; immunity; lymphocytes; macrophage; stroke