Comparison of expression profile of neurotrophins and their receptors in primary and transformed rat retinal ganglion cells

Purpose: To determine the expression profile of neurotrophins and their receptors in cultured primary rat retinal ganglion cells (RGCs) and the transformed RGC-5 cells. Methods: Confocal microscopic immunocytochemistry with double fluorescent labeling with thy-1 as a marker for RGCs was used to demonstrate expression of neurotrophins and their receptors. An enzyme-linked immunosorbent assay (ELISA) was used to detect secretion of neurotrophins by RGC-5 cells. Results: Primary RGCs and RGC-5 cells expressed brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrohin-3 (NT3), neurotrophin-4 (NT4), and receptors TrkA, p75, with low levels of TrkB. However, minimal if any, expression of TrkC was observed in these cells. RGC-5 cells also secreted NT3 (1311±21 pg/ml), BDNF (92±9 pg/ml), NGF (86±7 pg/ml), and NT4 (21±1 pg/ ml) into the cultured media. Conclusions: These results demonstrated that neurotrophins and TrkA, p75 with low levels of TrkB receptors are expressed by RGCs. Specific neurotrophins acting through TrkA, TrkB, and p75 receptors within the RGCs may be involved in the survival and apoptosis of the RGCs in various retinopathies, such as glaucoma.