Abstract
Purpose: :
Glial cell line-derived neurotrophic factor (GDNF) has known neuroprotective effects on photoreceptors in animal models of retinal degeneration and transplanted retinal progenitor cells (RPCs) represent a potential delivery method. Here we investigate the effect of GDNF on RPCs survival, proliferation and marker expression.
Methods: :
RPCs originally isolated from the neural retina of postnatal day-1 GFP-transgenic mice, and were cultured in the presence of epidermal growth factor (EGF) and/or GDNF (all 20 ng/ml) as follows: 1) no recombinant factors, 2) EGF alone, 3) GDNF alone, 4) EGF + GDNF. After 5 days, morphology and cell growth were assessed and expression of selected progenitor and retinal markers was evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR).
Results: :
Murine RPCs exhibited exponential growth in the presence of EGF alone, as well as with EGF + GDNF, but diminished asymptotically in the absence of both factors, or with GDNF alone. The morphology of RPCs likewise corresponded to the presence or absence of EGF, showing increased processes extension of processes upon growth factor removal consistent with spontaneous differentiation, whereas no changes were attributable to the presence of GDNF. In the presence of EGF, cultured RPCs expressed the progenitor markers nestin, ki-67, chx-10, sox2, c-myc, as well as vimentin, and this pattern was sustained for EGF + GDNF. Similarly, the expression levels of precursor and lineage-related markers including beta-III-tubulin, MAP2, DCX, CRALBP, PKC-alpha and recoverin were relatively unaffected by the addition of GDNF to EGF-based proliferation medium.
Conclusions: :
This study confirms the dependence of cultured murine RPCs on EGF and shows that GDNF alone is unable to sustain proliferation of these cells. RPCs growth and marker expression in the presence of EGF + GDNF are attributable to the effects of EGF alone, suggesting that the influence of GDNF was minimal and that in vitro expansion of constitutively GDNF-expressing RPCs may be feasible.
Keywords: regeneration • retina • transplantation