title: Variable functional recovery and minor cell loss in the ganglion cell layer of the lizard Gallotia galloti after optic nerve axotomy.
abstract: The lizard Gallotia galloti shows spontaneous and slow axon regrowth through a permissive glial scar after optic nerve axotomy. Although much of the expression pattern of glial, neuronal and extracellular matrix markers have been analyzed by our group, an estimation of the cell loss in the ganglion cell layer (GCL) and the degree of visual function recovery remained unresolved. Thus, we performed a series of tests indicative of effective visual function (pupillary light reflex, accommodation, visually elicited behavior) in 18 lizards at 3, 6, 9 and 12 months post-axotomy which were then processed for immunohistochemistry for the neuronal markers SMI-31 (neurofilaments), Tuj1 (beta-III tubulin) and SV2 (synaptic vesicles) at the last timepoint. Separately, cell loss in the GCL was estimated by comparative quantitation of DAPI(+) nuclei in control and 12 months experimental lizards. Additionally, 15 lizards were processed for electron microscopy to monitor relevant ultrastructural changes in the GCL, optic nerve and optic tract throughout regeneration. Hypertrophy of RGCs was persistent, morphology of the regenerated nerves varied from narrow to neuroma-like features and larger regenerated axons underwent remyelination by 9 months. The estimated cell loss in the GCL was 27% and two-third of the animals recovered the pupillary light reflex which involves the pretectum. Strikingly, visually elicited behavior involving the tectum was only restored in two specimens, presumably due to the higher complexity of this pathway. These preliminary results indicate that limited functional regeneration occurs spontaneously in the severely injured visual system of the lacertid G. galloti.
authors.affiliation: Departamento de Microbiología y Biología Celular, Universidad de La Laguna, 38206 Tenerife (Canary Islands), Spain; Departamento de Morfología (Biología Celular), Universidad de Las Palmas de Gran Canaria, 35016 Gran Canaria (Canary Islands), Spain. Electronic address: esantos@ull.es.
authors.forename: E
authors.initials: E
authors.lastname: Santos
authors.affiliation: Departamento de Morfología (Biología Celular), Universidad de Las Palmas de Gran Canaria, 35016 Gran Canaria (Canary Islands), Spain.
authors.forename: M M
authors.initials: MM
authors.lastname: Romero-Alemán
authors.affiliation: Departamento de Morfología (Biología Celular), Universidad de Las Palmas de Gran Canaria, 35016 Gran Canaria (Canary Islands), Spain.
authors.forename: M
authors.initials: M
authors.lastname: Monzón-Mayor
authors.affiliation: Departamento de Microbiología y Biología Celular, Universidad de La Laguna, 38206 Tenerife (Canary Islands), Spain.
authors.forename: C
authors.initials: C
authors.lastname: Yanes
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D019771:Axotomy / Q000379:methods*; D004195:Disease Models, Animal; D008116:Lizards; D009416:Nerve Regeneration / Q000502:physiology*; D009900:Optic Nerve / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D020221:Optic Nerve Injuries / Q000473:pathology / Q000503:physiopathology*; D020127:Recovery of Function; D012165:Retinal Ganglion Cells / Q000473:pathology*; D014785:Vision, Ocular / Q000502:physiology*
keywords: CNS; GCL; NFL; OCh; OT; OTr; Pia; RGCs; axon regrowth; central nervous system; ganglion cell layer; nerve fiber layer; optic chiasm; optic tectum; optic tract; piamater; pupillary light reflex; regeneration; reptile; retinal ganglion cells; sfgs; so; stratum fibrosum et griseum superficialis; stratum opticum; vision