Neuroprotective effect of transpupillary thermotherapy in the optic nerve crush model of the rat

Transpupillary thermotherapy (TTT) has been shown to induce heat shock protein (Hsp) 72 in optic nerve head tissue. The neuroprotective effect of TTT was investigated in an optic nerve crush rat model.TTT was performed onto the optic nerve head in the right eye of subject rats. After 24 h, an optic nerve crush injury using an aneurysm clip was performed at 2 mm from the optic nerve head for 60 s. At 7 and 14 days later, retrograde labelling of retinal ganglion cells (RGCs) with DTMR crystal was carried out and the density of the surviving RGCs was evaluated. Immunohistochemical staining was performed to confirm the expression of Hsp72.At 7 days after optic nerve crush injury, the mean density of surviving RGCs was higher in TTT group (372.7+/-149.8 per mm(2)) than in optic nerve crush group (252.9+/-96.7 per mm(2)) with borderline significance. In the retinal areas at 1 mm from the optic nerve head, a significant increase in surviving RGCs from TTT treated eyes was observed at both 7 and 14 days after optic nerve crush injury. However, no significant differences in surviving RGCs were demonstrated 2 and 3 mm from the optic nerve head.These results demonstrate that TTT aimed onto the optic nerve head showed a neuroprotective effect.