title: Neuroprotective effect on retinal ganglion cells by transpupillary laser irradiation of the optic nerve head.
abstract: This study demonstrates that subthreshold transpupillary thermotherapy (TTT) laser irradiation on optic nerve head protects retinal ganglion cells (RGCs) in an optic nerve crush (ONC) model. TTT was performed in right eyes with an 810-nm diode laser aimed at the center of the optic nerve head, using the following protocol: power 60mW, duration 60s, spot size 500mum. Fluoro-Gold was injected into bilateral superior colliculi 5 days before sacrifice and fluorescent gold labeled RGCs were counted under fluorescence microscopy. In the ONC group, a progressive loss of RGCs was observed; however, in comparison with the ONC group, RGCs density was significantly higher (P=0.001, independent samples t-test) at day 7 postoperative and only borderline significances were obtained at days 14 and 28 postoperative (P=0.044 and P=0.045, respectively, independent samples t-test) in ONC+TTT group, which implies the potential neuroprotective role of TTT. This protective effect seems to be heat shock proteins (HSPs) related, because intraperitoneal Quercetin (an inhibitor of HSPs, 4mg/kg/day for 7 days) could completely abolish this protective effect at days 7, 14 and 28 postoperative (P=0.012, P=0.002, and P=0.000, respectively, independent samples t-test). Minimal collateral damage of TTT on optic nerve head tissue, peripapillary RGCs and the myelin sheath of the optic nerve were observed under transmission electron microscopy. These findings suggested that subthreshold TTT might be a safe and practical approach to protect RGCs. The underlying mechanisms may involve TTT-induced HSPs in RGCs.
authors.affiliation: Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, PR China.
authors.forename: Jin
authors.initials: J
authors.lastname: Ma
authors.forename: Libin
authors.initials: L
authors.lastname: Jiang
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhong
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Chan
authors.initials: C
authors.lastname: Zhao
authors.forename: Fangtian
authors.initials: F
authors.lastname: Dong
mesh_terms: D000818:Animals; D002470:Cell Survival; D005260:Female; D006979:Hyperthermia, Induced; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D028022:Low-Level Light Therapy; D009409:Nerve Crush; D009900:Optic Nerve / Q000473:pathology / Q000528:radiation effects*; D020221:Optic Nerve Injuries / Q000473:pathology / Q000532:radiotherapy; D011680:Pupil; D051381:Rats; D012165:Retinal Ganglion Cells / Q000473:pathology / Q000528:radiation effects*