title: IOP induces upregulation of GFAP and MHC-II and microglia reactivity in mice retina contralateral to experimental glaucoma.
abstract: BACKGROUND
  Ocular hypertension is a major risk factor for glaucoma, a neurodegenerative disease characterized by an irreversible decrease in ganglion cells and their axons. Macroglial and microglial cells appear to play an important role in the pathogenic mechanisms of the disease. Here, we study the effects of laser-induced ocular hypertension (OHT) in the macroglia, microglia and retinal ganglion cells (RGCs) of eyes with OHT (OHT-eyes) and contralateral eyes two weeks after lasering.
  
  
  METHODS
  Two groups of adult Swiss mice were used: age-matched control (naïve, n=9); and lasered (n=9). In the lasered animals, both OHT-eyes and contralateral eyes were analyzed. Retinal whole-mounts were immunostained with antibodies against glial fibrillary acid protein (GFAP), neurofilament of 200 kD (NF-200), ionized calcium binding adaptor molecule (Iba-1) and major histocompatibility complex class II molecule (MHC-II). The GFAP-labeled retinal area (GFAP-RA), the intensity of GFAP immunoreaction (GFAP-IR), and the number of astrocytes and NF-200 + RGCs were quantified.
  
  
  RESULTS
  In comparison with naïve: i) astrocytes were more robust in contralateral eyes. In OHT-eyes, the astrocyte population was not homogeneous, given that astrocytes displaying only primary processes coexisted with astrocytes in which primary and secondary processes could be recognized, the former having less intense GFAP-IR (P<0.001); ii) GFAP-RA was increased in contralateral (P<.05) and decreased in OHT-eyes (P <0.001); iii) the mean intensity of GFAP-IR was higher in OHT-eyes (P<0.01), and the percentage of the retinal area occupied by GFAP+ cells with higher intensity levels was increased in contralateral (P=0.05) and in OHT-eyes (P<0.01); iv) both in contralateral and in OHT-eyes, GFAP was upregulated in Müller cells and microglia was activated; v) MHC-II was upregulated on macroglia and microglia. In microglia, it was similarly expressed in contralateral and OHT-eyes. By contrast, in macroglia, MHC-II upregulation was observed mainly in astrocytes in contralateral eyes and in Müller cells in OHT-eyes; vi) NF-200+ RGCs (degenerated cells) appeared in OHT-eyes with a trend for the GFAP-RA to decrease and for the NF-200+RGC number to increase from the center to the periphery (r= -0.45).
  
  
  CONCLUSIONS
  The use of the contralateral eye as an internal control in experimental induction of unilateral IOP should be reconsidered. The gliotic behavior in contralateral eyes could be related to the immune response. The absence of NF-200+RGCs (sign of RGC degeneration) leads us to postulate that the MHC-II upregulation in contralateral eyes could favor neuroprotection.
authors.affiliation: Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Universidad Complutense de Madrid, Madrid, 28040, Spain.
authors.forename: Beatriz I
authors.initials: BI
authors.lastname: Gallego
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Salazar
authors.forename: Rosa
authors.initials: R
authors.lastname: de Hoz
authors.forename: Blanca
authors.initials: B
authors.lastname: Rojas
authors.forename: Ana I
authors.initials: AI
authors.lastname: Ramírez
authors.forename: Manuel
authors.initials: M
authors.lastname: Salinas-Navarro
authors.forename: Arturo
authors.initials: A
authors.lastname: Ortín-Martínez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Valiente-Soriano
authors.forename: Marcelino
authors.initials: M
authors.lastname: Avilés-Trigueros
authors.forename: Maria P
authors.initials: MP
authors.lastname: Villegas-Perez
authors.forename: Manuel
authors.initials: M
authors.lastname: Vidal-Sanz
authors.forename: Alberto
authors.initials: A
authors.lastname: Triviño
authors.forename: Jose M
authors.initials: JM
authors.lastname: Ramírez
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000473:pathology; D002452:Cell Count; D005901:Glaucoma / Q000378:metabolism* / Q000473:pathology; D005904:Glial Fibrillary Acidic Protein; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D007429:Intraocular Pressure / Q000235:genetics / Q000502:physiology*; D008297:Male; D051379:Mice; D017628:Microglia / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009798:Ocular Hypertension / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012160:Retina / Q000378:metabolism* / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D005904:Glial Fibrillary Acidic Protein; D000949:Histocompatibility Antigens Class II; D009419:Nerve Tissue Proteins; C528900:glial fibrillary astrocytic protein, mouse