Purpose: To investigate the expression and possible neuroprotective effects of hepatocyte growth factor (HGF) in a rat model of retinal ischemia-reperfusion injury.
Methods: Retinal ischemia was induced in adult male Sprague-Dawley rats by raising the intraocular pressure to 110 mm Hg for 45 minutes. To study expression of HGF and its receptor c-Met, reverse transcription-polymerase chain reaction (RT-PCR), Western blot analysis, and immunohistochemical staining were performed on eyes enucleated at 6, 12, 24, 48, and 96 hours after reperfusion. To examine the neuroprotective effects of HGF, recombinant human (rh)HGF (1, 6, and 12 microg in 2 microL PBS) or vehicle was administered intravitreally 1 minute after reperfusion, and the eyes were enucleated at 6, 12, 24, 48, and 96 hours and 28 days after reperfusion. The retinal damage was assessed by electroretinogram (ERG) recordings, by measuring the inner retinal thickness, and by counting the number of TUNEL-positive cells in each retinal layer.
Results: RT-PCR and Western blot analyses showed upregulation of HGF and c-Met-HGF receptor mRNA at 6, 12, 24, and 48 hours after reperfusion, compared with the normal rat retina. Immunohistochemically, expression of HGF was found in the retinal pigment epithelial cells at 6 hours after reperfusion and in some cells in the ganglion cell layer and inner nuclear layer at 24 hours after reperfusion. The amplitudes of the ERG b-wave and oscillatory potentials were significantly larger in the eyes treated with 6 and 12 microg rhHGF than in those of vehicle-treated control rats (P < 0.01). On day 28, the thicknesses of the inner retina of vehicle-treated rats and that of 6-microg rhHGF-treated rats were 54.4 +/- 6.12 (mean +/- SD, n = 9) and 71.5 +/- 9.81 microm (n = 8), respectively (P < 0.01). The number of TUNEL-positive cells at 6, 12, 24, and 48 hours after reperfusion was decreased significantly by treatment with 6 microg rhHGF, compared with those in the control rats (P < 0.01).
Conclusions: Upregulation of HGF in the retina may play a role in retinal ischemia-reperfusion injury. Intravitreal injection of rhHGF is neuroprotective against the injury.