Overlapping and additive effects of neurotrophins and CNTF on cultured human spinal cord neurons.

Ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) have been shown both in vitro and in vivo to support the survival and differentiation of developing chick or rat motoneurons. To explore the potential use of these and other neurotrophic factors as therapeutic agents in human motoneuron diseases, we have examined the effects of the neurotrophins NGF, BDNF, neurotrophin-3 (NT-3), and neurotrophin-4/5 (NT-4/5) and the cytokines CNTF and cholinergic differentiation factor/leukemia inhibitory factor (CDF/LIF) and combinations of these factors on fetal human spinal cord neurons grown for 7-10 days in monolayer cultures. The level of choline acetyltransferase (ChAT) was determined in cultures grown in the presence of NGF, BDNF, NT-3, NT-4/5, CNTF, or CDF/LIF or with combinations of these factors. With the exception of NGF, each of these factors alone increased ChAT activity by two- to three-fold above control levels; combinations of NT-3 and CNTF were greater than either alone. As a single factor NT-4/5 produced the greatest increase in ChAT activity, but was not additive with any other neurotrophin or CNTF. A combination of the three factors CNTF, BDNF, and NT-3 or the four factors CNTF, BDNF, NT-3, and NT-4 increased ChAT levels by four-fold, an effect greater than any individual factor. The finding that combinations of these factors show some additive effects toward human spinal cord cholinergic neurons in culture has prompted the testing of such combinations in animal models of motoneuron disease.