Leukemia Inhibitory Factor and Neurotrophins Support Overlapping Populations of Rat Nodose Sensory Neurons in Culture

Abstract

Recent studies in this and other laboratories demonstrated that leukemia inhibitory factor (LIF) can regulate differentiation and survival of nerve growth factor (NGF)-dependent primary sensory neurons. To determine whether development of NGF-independent sensory neurons could be similarly regulated, the present study examined the effects of LIF and the related cytokine-like growth factor, ciliary neurotrophic factor (CNTF), on survival of rat nodose ganglion (NG) cells in culture. In addition, survival in LIF-treated cultures was compared in the presence and absence of the neurotrophins brain-derived neurotrophic factor (BDNF), NT-3, and NT-4, factors previously shown to target NG sensory neurons, to determine whether the cytokine-like factors and neurotrophins act on the same population of ganglion cells. Treatment of dissociate cultures of Embryonic Day (E) 16.5 NG with LIF or CNTF (10 ng/ml) resulted in a four- to fivefold increase in neuronal survival; the number of neurons supported by either factor represented approximately 50% of the total NG population. In contrast, less than 10% of newborn NG neurons survived in the presence of LIF or CNTF, suggesting a loss in responsiveness to these factors during fetal development in vivo. In cultures of E16.5 ganglia, BDNF, NT-3, or NT-4 alone each increased cell survival to varying degrees (BDNF > NT-4 = LIF > NT-3); NGF, on the other hand, had no effect. Combining LIF with BDNF, NT-3, or NT-4 had only partially additive effects on NG neuron number (LIF + BDNF, 36% greater than BDNF alone; LIF + NT-3, 21% greater than LIF alone; LIF + NT-4, 49% greater than NT-4 or LIF alone; P < 0.05), indicating that LIF and these neurotrophins support survival of overlapping subsets of NG neurons in culture. To begin defining whether NG neurons were capable of responding to CNTF and LIF in vivo, Northern blots were used to examine expression of mRNAs coding for CNTF and LIF receptor components (CNTFRα, gp130, and LIFRβ) in the intact ganglion. mRNAs for all three receptor components were present in both E16.5 and newborn ganglia, suggesting that LIF and CNTF receptors are expressed in the NG in vivo. Taken together, these data demonstrate that LIF and CNTF can support survival of NGF-independent sensory neurons in culture and indicate that cytokine-like growth factors may play a role in regulating visceral sensory development in vivo.