Elsevier

Neuroscience

Volume 146, Issue 2, 11 May 2007, Pages 833-840
Neuroscience

Sensory system
Culture conditions determine the prevalence of bipolar and monopolar neurons in cultures of dissociated spiral ganglion

https://doi.org/10.1016/j.neuroscience.2007.01.036Get rights and content

Abstract

To gain insight into the mechanisms that control the generation or maintenance of the characteristic bipolar morphology of cochlear spiral ganglion neurons, we have taken advantage of our recently developed procedure for culture of dissociated newborn mouse spiral ganglion. In these cultures, inclusion of the cytokine leukemia inhibitory factor (LIF) in the medium increases neuronal survival and the number of bipolar neurons. Here we tested effects of two other LIF-type cytokines (ciliary neurotrophic factor, CNTF; and human recombinant oncostatin M, hOSM) and of bone morphogenetic protein 4 (BMP4) on survival, morphology and neurite lengths of neurons in cultures of dissociated spiral ganglion. Like LIF, CNTF and hOSM increased neuronal survival and the number of surviving bipolar neurons. BMP4 also increased neuronal survival, but unlike LIF, CNTF and hOSM, increased the number of monopolar neurons and neurons with no neurites. In addition, population histograms demonstrate that the population lengths of the longer and shorter neurites of bipolar neurons were shorter in BMP4 containing cultures than in control or LIF cultures. When LIF and BMP4 were simultaneously added to the cultures, the BMP4 effects predominated. These experiments demonstrate that exposure to different environmental conditions can result in different morphologies in the surviving population of spiral ganglion neurons in culture.

Section snippets

Animals

Newborn and postnatal day 1 mice, CD-1 strain (Charles River Laboratories, Wilmington, MA, USA) were used. The care and use of the animals in this study were carried out in accordance with the NIH Guide for the Care and Use of Laboratory Animals and was approved by the Animal Care and Use Committee of Northwestern University. Every effort was made to minimize the suffering of research animals and to limit their numbers.

Cell culture

Cultures of dissociated spiral ganglion in 96-well plates were prepared as

Results

We previously demonstrated that neuronal survival 42 h after plating could be increased when LIF was added to the control conditions of BDNF+NT3+serum. This additional survival in LIF cultures was associated with an increase in the absolute number of bipolar neurons over that in control cultures (Whitlon et al., 2006). Signaling by LIF is known to be initiated at the cell surface through the LIFRβ-gp130 receptor. To determine if other cytokines that are known to function through the LIFRβ-gp130

Discussion

In this study, we have exposed spiral ganglion cultures to neurotrophins, LIF-type cytokines and BMP4 and examined the resulting neuronal survival, morphology and neurite lengths. Under all conditions, monopolar neurons, bipolar neurons and neurons with no neurites comprise over 95% of the neurons in the culture. However, the relative contributions of the different morphologies differ between control, LIF and BMP4 conditions. Specifically, as compared with control, inclusion of LIF type

Acknowledgments

The authors appreciate the advice of Dr. Adriana Ferreira on neuronal cell cultures. We thank Dr. Ferreira, Dr. James Bartles and Dr. David Tieu for their insightful comments on the manuscript. This work was supported by NIH grant #DC00653.

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