Gene therapy for detached retina by adeno-associated virus vector expressing glial cell line-derived neurotrophic factor.
OBJECTIVE
To examine the protective effect of glial cell line-derived neurotrophic factor (GDNF) on retinal detachment (RD)-induced photoreceptor damage by using gene delivery.


METHODS
Gene delivery to photoreceptors was achieved by subretinal injection of recombinant adeno-associated virus expressing GDNF (rAAV-GDNF) in the right eyes and AAV expressing Escherichia coli LacZ (rAAV-LacZ) in the left eyes of Lewis rats. RD in bilateral eyes was induced with subretinal injection of high-density vitreous substitute in the temporal retina 3 weeks after gene delivery. The synthesis and accumulation of GDNF within the retina was monitored 3 weeks after RD by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), respectively. The rescue of photoreceptors was evaluated by monitoring the preservation of the thickness of photoreceptor outer segment (OS) and outer nuclear layer (ONL). Apoptosis in the photoreceptors was studied using the TdT-dUTP terminal nick-end labeling (TUNEL) method 2 days after RD. Müller cell activity was checked using the immunohistochemistry with glial fibrillary acidic protein (GFAP) antibody 28 days after RD.


RESULTS
Gene delivery was demonstrated by immunohistochemical study. The results of ELISA confirmed that high levels of neurotrophic factors were produced in retinas. Photoreceptor OS degeneration and the gradual shortening of the ONL were noted after RD in all the eyes. However, rAAV-GDNF-treated eyes retained longer OS than rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. ONL was also longer in rAAV-GDNF-treated eyes than in rAAV-LacZ-treated eyes 7 (P = 0.012) and 28 days (P = 0.008) after RD. GDNF-treated eyes had statistically less apoptotic cells than control eyes in photoreceptor layer (P = 0.043). Subretinal proliferation of Müller cells was suppressed in the GDNF-treated group, indicating less scar formation.


CONCLUSIONS
GDNF is a potential factor that can protect photoreceptors from degeneration. In addition to preserving the OS and ONL structures, GDNF may exert its protective action by preventing the apoptosis of photoreceptors after RD. GDNF gene therapy may be a valuable adjuvant to current treatments in certain complicated forms of RD.
Wu
Wei-Chi
WC
Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.
Lai
Chi-Chun
CC
Chen
Show-Li
SL
Xiao
Xiao
X
Chen
Tun-Lu
TL
Tsai
Ray Jui-Fang
RJ
Kuo
Shu-Wen
SW
Tsao
Yeou-Ping
YP
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D019610:Cytoprotection; D000229:Dependovirus / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D015316:Genetic Therapy; D005822:Genetic Vectors; D051100:Glial Cell Line-Derived Neurotrophic Factor; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D009414:Nerve Growth Factors / Q000096:biosynthesis / Q000235:genetics*; D009457:Neuroglia / Q000378:metabolism; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D011917:Rats, Inbred Lew; D012163:Retinal Detachment / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D014162:Transfection; D001616:beta-Galactosidase / Q000235:genetics
C495041:Gdnf protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D001616:beta-Galactosidase