Glial Cell Line-Derived Neurotrophic Factor Stimulates the Morphological Differentiation of Cultured Ventral Mesencephalic Calbindin- and Calretinin-Expressing Neurons

Abstract

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for mesencephalic dopaminergic neurons. Subpopulations of these neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Understanding the specific effects of GDNF on these neurons is important for the development of an optimal cell replacement therapy for Parkinson's disease. To investigate the effects of GDNF on the morphological complexity of mesencephalic tyrosine hydroxylase (TH)-immunoreactive (-ir), CB-ir, and CR-ir neurons, dissociated cultures of embryonic (E14) rat ventral mesencephalon were prepared. Chronic administration of GDNF (10 ng/ml) for 7 days promoted the survival of TH-ir and CB-ir neurons but did not alter the density of CR-ir neurons. Total fiber length/neuron and number of branching points/neuron of CB-ir and CR-ir cells were significantly increased after GDNF treatment (2× for CB-ir cells and 1.4× and 1.7×, respectively, for CR-ir cells), which resulted in a significantly larger size of neurite field/neuron (2.9× and 1.5× for CB-ir and CR-ir neurons, respectively). The number of primary neurites/neuron of CB-ir neurons was found to be 1.5× larger, while no difference could be detected for CR-ir cells. Assessment of the effects of GDNF on TH-ir neurons unveiled a similar outcome with an increased total fiber length/neuron (1.5×), an increased number of primary neurites/neuron (1.6×), and a twofold larger size of neurite field/neuron. In conclusion, our findings recognize GDNF as a neurotrophic factor that stimulates the morphological differentiation of ventral mesencephalic CB-ir and CR-ir neurons.