| Summary: | 碩士 === 國立陽明大學 === 臨床醫學研究所 === 96 === Background/Aims: This study was designed to evaluate the neuroprotective potential of subretinal gene transfer of glial cell line-derived neurotrophic factor (GDNF) to ameliorate light-induced photoreceptor cell degeneration.
Methods: Sprague-Dawley albino rats received subretinal injections of recombinant adeno-associated viral vector (rAAV) expressing GDNF in the right eyes and rAAV expressing Escherichia coli LacZ (rAAV-LacZ) in the left eyes. Three weeks after gene delivery, retinal light damage was introduced by exposing the rats to 13,000 lux white fluorescent light for two hours. Synthesis of GDNF within the neurosensory retina was confirmed by Western blot analysis and immunohistochemiscal stain. Photoreceptor rescue was evaluated by cell counts of the outer nuclear layer (ONL). Apoptosis of photoreceptors were studies by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) 24 hours after light damage. Electroretinograms (ERG) were performed to examine the changes of retinal functions.
Results: GDNF were expressed in rAAV-GDNF-injected retina as demonstrated by Western blot analysis and immunohistochemical stain. Thinning of the outer retina, outer segment of photoreceptors and decreased nuclei numbers of the ONL were observed in all light-damaged eyes. Seven days after light exposure, the rAAV-GDNF-injected eyes retained larger b-wave amplitude than rAAV-LacZ-injected and naïve untreated eyes (p=0.046 and p=0.002, respectively). Cell counts revealed a greater number of photoreceptors after rAAV-GDNF injection as compared to than rAAV-LacZ injection (p<0.05) or no treatment (p<0.05). Measurement of ONL thickness also demonstrated a significant protective effect of rAAV-GDNF. Finally, significantly fewer TUNEL-positive photoreceptor nuclei were present in rAAV-GDNF-injected eyes than rAAV-LacZ-injected eyes (p=0.043) or naïve untreated eyes (p=0.008).
Conclusions: These data demonstrate that subretinal GDNF gene transfer has the capacity to attenuate light-induced photoreceptor cell death in rats. Both the morphology and function of the retina were preserved. The possible protective mechanism of GDNF is through an anti-apoptotic effect.
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