GDNF regulates chicken rod photoreceptor development and survival in reaggregated histotypic retinal spheres.
OBJECTIVE
To investigate the role of glial-cell-line-derived neurotrophic factor (GDNF) on proliferation, differentiation, and apoptosis of different retinal cell types--in particular, photoreceptor cells.


METHODS
Reaggregated histotypic spheres, derived from retinal cells of the E6 chicken embryo were used. Under rotation, so-called rosetted spheroids arose by aggregation of dissociated retinal cells, followed by the proliferation, migration, differentiation and programmed cell death of particular cell types. Rosetted spheroids were cultured under serum-reduced conditions, either in the absence or presence of 50 ng/mL GDNF. At appropriate stages, rosetted spheroids were analyzed by using conventional staining and immunolabeling with antibodies against different retinal cell types.


RESULTS
At early stages of culture, the application of GDNF to rosetted spheroids significantly increased and sustained the rate of proliferation. In particular, a de novo production of rod photoreceptors was observed, whereas cone photoreceptors and amacrine, horizontal, ganglion, and Müller cells were not affected. In addition, in GDNF-treated cultures, rod photoreceptors differentiated earlier than in nontreated cultures. In older rosetted spheroids raised in absence of GDNF, rod but not cone photoreceptors underwent apoptosis. By supplementation with GDNF, the percentage of dying rod photoreceptors was dramatically reduced (31%-6% at 8 days in culture, 71%-3% at 10 days in culture). Both the mitogenic and survival promoting effect of GDNF were dose dependent.


CONCLUSIONS
The results strongly suggest that GDNF, at least in vitro, affects rod photoreceptors. Depending on the developmental stage, GDNF regulates their proliferation, differentiation, and survival.
Rothermel
Andrée
A
Darmstadt University of Technology, Developmental Biology and Neurogenetics, Darmstadt, Germany. rothermel@bio.tu-dermstadt.de
Layer
Paul G
PG
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002452:Cell Count; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D019084:Fluorescent Antibody Technique, Indirect; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000196:embryology*; D018874:Spheroids, Cellular
D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D018696:Neuroprotective Agents