title: Peripheral nerve injury induces aquaporin-4 expression and astrocytic enlargement in spinal cord.
abstract: Aquaporin-4 (AQP4), a water channel protein, is expressed mainly in the perivascular end-feet of astrocytes in the brain and spinal cord. Dysregulation of AQP4 is critically associated with abnormal water transport in the astrocytes. We aimed to examine whether peripheral nerve injury (PNI) could induce the changes of AQP4 expression and astrocytic morphology in the spinal cord. Two different PNI models [partial sciatic nerve transection (PST) and chronic constriction injury (CCI)] were established on the left sciatic nerve in Sprague-Dawley rats, which decreased the pain withdrawal threshold in the ipsilateral hind paws. Both PNI models were associated with a persistent up-regulation of AQP4 in the ipsilateral dorsal horn at the lower lumbar region over 3 weeks, despite an absence of direct injury to the spinal cord. Three-dimensional reconstruction of astrocytes was made and morphometric analysis was done. Up-regulation of AQP4 was accompanied by a significant increase in the length and volume of astrocytic processes and the number of branch points. The most prominent changes were present in the distal processes of the astrocytes and the changes were maintained throughout the whole experimental period. Extravasation of systemically administered tracers Evans Blue and sodium fluorescein was not seen in both models. Taken together, PNI was associated with a long-lasting AQP4 up-regulation and enlargement of astrocytic processes in the spinal cord in rats, both of which were not related to the disruption of blood-spinal cord barrier. The findings could provide novel insights on the understanding of pathophysiology of spinal cords after PNI.
authors.affiliation: Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu 41944, South Korea.
authors.forename: M K
authors.initials: MK
authors.lastname: Oklinski
authors.affiliation: Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu 41944, South Korea.
authors.forename: H-J
authors.initials: HJ
authors.lastname: Choi
authors.affiliation: Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, Taegu 41944, South Korea. Electronic address: thkwon@knu.ac.kr.
authors.forename: T-H
authors.initials: TH
authors.lastname: Kwon
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D001253:Astrocytes / Q000473:pathology* / Q000502:physiology; D048429:Cell Size; D004195:Disease Models, Animal; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D007839:Functional Laterality / Q000502:physiology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D006614:Hindlimb / Q000503:physiopathology; D008159:Lumbar Vertebrae; D008297:Male; D017288:Pain Threshold / Q000502:physiology; D059348:Peripheral Nerve Injuries / Q000473:pathology* / Q000503:physiopathology*; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000293:injuries; D013116:Spinal Cord / Q000473:pathology* / Q000503:physiopathology*
chemical_list: C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; C493395:Slc1a2 protein, rat; D005974:Glutamate-Ammonia Ligase
keywords: aquaporin-4; astrocyte enlargement; morphometric analysis; peripheral nerve injury; spinal cord