Olfactory sensory neurons are continually replaced throughout life and their rate of generation increases after injury. This does not occur in the brain and spinal cord, where injuries cause devastating clinical problems. We have proposed that the uniqueness of the olfactory system results from the fact that the tissue microenvironment is unusual and are characterizing factors (cells and molecules) that regulate olfactory neurogenesis. Eventually, we hope this will lead to new treatments for brain and spinal cord injuries. To identify factors, we have developed novel cell culture systems from rats and transgenic mice in which the neurons aggregate into cavity-bearing cellular spheres that we have called "micro-noses". There, the neurons re-form cell-cell relationships normally found in the intact animal, and they undergo constant generation and turnover. We are using this system to characterize trophic factors, including those provided by the olfactory neuron target tissue, the olfactory bulb, and those provided by the support cells surrounding the neurons.
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