Conditioned medium from aged monkey fibroblasts stably expressing GDNF and BDNF improves survival of embryonic dopamine neurons in vitro

Fibroblasts derived from the cerebral cortex of an aged Bonnet monkey (Macaca radiata) were utilized to express recombinant cDNAs encoding rat glial-cell-line-derived neurotrophic factor (GDNF) and human prepro brain-derived neurotrophic factor (BDNF) by lipofection. The cells showed stable expression and secretion of biologically active proteins. Conditioned medium from fibroblasts expressing BDNF or GDNF increased the number of surviving mesencephalic tyrosine-hydroxylase-immunoreactive neurons after 7 days in culture. The trophic effects of BDNF and CDNF were examined at two different plating densities of embryonic mesencephalic cells. At 50000 cells/cm(2) plating density, treatment of the mesencephalic cultures with BDNF-conditioned medium increased the number of tyrosine-hydroxylase-immunoreactive neurons by about 40% compared with vector-transfected control. At the same plating density, GDNF-conditioned medium increased the number of surviving tyrosine-hydroxylase-immunoreactive neurons above the vector-transfected control by 30%. When the tissue was plated at a higher density, viz., 75000 cells/cm(2), the number of tyrosine-hydroxylase-immunoreactive neurons increased by 41% with BDNF-conditioned medium, and by 56% with GDNF-conditioned medium above vector-transfected controls. Conditioned medium from cells secreting GDNF was also found to reduce the number of apoptotic tyrosine-hydroxylase-immunoreactive cells by 50%.