Abstract
Purpose::
To investigate the role of the cytokines glial cell line derived neurotrophic factor (GDNF), pigment epithelial derived factor (PEDF) and brain derived neurotrophic factor (BDNF) on proliferation, differentiation and apoptosis of retinal cell types in a 3D environment using reaggregated histiotypic spheres of the chicken E6 retina.
Methods::
Rotation culture conditions were used to form rosetted spheroids from dissociated retinal cells. The proliferation, migration and differentiation of cells into histiotypic spheres were followed using BrdU to measure proliferation and cell type specific markers to measure differentiation.
Results::
At early stages of spheroid culture all three cytokines promoted a sustained increase in the rate of cell proliferation and a significant decrease in the number of apoptotic cells in the spheres. At day 10 the percentage of apoptotic cells was 32% in controls, 8% with PEDF treatment, and 6% in GDNF or BDNF supplemented cultures. GDNF treatment increased the number and early differentiation of rod photoreceptors. These cultures also showed a reduced number of dying rods. In cultures treated with PEDF the number of cone photoreceptors was more than doubled at day 8 but there was a decrease in the number of rods from 4% in controls to 0.5% with PEDF treatment. BDNF affected primarily cells of the inner retina with a significant increase in the number of amacrine cells at day 4 form 35% in controls to 53% in treated cultures.
Conclusions::
GDNF promotes the differentiation of rod photoreceptors whereas PEDF promotes cone photoreceptor formation and inhibits rod formation. BDNF acts primarily to promote formation of cells of the inner retina. The 3D spheroid model is useful for the detailed analysis of the mechanisms of cytokine action, individually or in combination, in retinal tissue formation.
Keywords: cytokines/chemokines • photoreceptors • retinal culture