Abstract
Purpose: :
To determine what growth factors are secreted by neural stem cells and retinal progenitor cells in conditioned media.
Methods: :
Neural stem cells (NSCs) were obtained from the National Human Neural Stem Cell Resource maintained by Children's Hospital of Orange County and grown according to their protocols in medium containing Epidermal Growth Factor (EGF), basic Fibroblast Growth Factor (bFGF), and Platelet–Derived Growth Factor (PDGF). Retinal progenitor cells (RPCs) were isolated from a human eye obtained less than 30 hours post–mortem from the Georgia Eye Bank. These cells were maintained in a medium containing both EGF and bFGF. All cells were fed forty eight hour feeding schedule. Media removed from the cells were retained and referred to as conditioned media (CM). Enzyme immunoassay kits from Chemicon were used to determine levels of Vascular Endothelial Growth Factor (VEGF) and Pigment Epithelium–Derived Factor (PEDF) present in both the growth medium added to the cells and the CM. A similar kit from Promega was used to determine levels of Nerve Growth Factor (NGF).
Results: :
VEGF levels in RPC growth medium were not detectable. In RPC–CM, however, the levels increased to 0.29ng/mL. VEGF levels in NSC growth medium were 0.34ng/mL. Levels in the conditioned medium increased four and a half fold to 1.58ng/mL. Thus far, PEDF and NGF levels have been undetectable in either the growth media or the conditioned media.
Conclusions: :
Neural stem cells and retinal progenitor cells secrete VEGF into their media as they grow. As the cells do not grow well without the addition of conditioned media, it is likely that this and other as yet unidentified growth factors act in an autocrine fashion to enhance survival and proliferation of the cells.
Keywords: growth factors/growth factor receptors • retinal degenerations: hereditary • proliferation