Related Experiment Videos
Changes in neuronal mRNAs induced by a local inflammatory reaction
1Division of Neurosurgery, McGill University, Montreal, Canada.
Abstract:
Injection of Corynebacterium parvum into the rat dorsal root ganglion has previously been shown to cause an inflammatory reaction dominated by macrophages and to enhance regeneration of the central axons of primary sensory neurons. Here, neuronal mRNAs that are modified by nerve transection were analyzed by in situ hybridization following injection of C. parvum into the dorsal root ganglion. Neuronal concentrations of mRNAs for the growth-associated protein (GAP-43) and the immediate early gene c-jun were increased by a local inflammatory response just as after axotomy. The concentration of mRNA for calcitonin gene-related peptide (CGRP) was also increased in a constant subpopulation of sensory neurons after injection of C. parvum in contrast to its decrease following axotomy. The results are consistent with the hypothesis that some of the responses to sensory neurons to axotomy are sustained by macrophages which accumulate within the dorsal root ganglion after nerve injury.
Insights
Injection of Corynebacterium parvum into dorsal root ganglia triggers inflammation and alters neuronal gene expression. Macrophages appear to sustain sensory neuron responses following nerve injury, promoting regeneration.
Area of Science:
- Neuroscience
- Immunology
- Molecular Biology
Background:
- Injection of Corynebacterium parvum into the dorsal root ganglion (DRG) induces a macrophage-dominated inflammatory response.
- This inflammatory response has been previously shown to enhance the regeneration of central axons in primary sensory neurons.
Purpose of the Study:
- To analyze neuronal mRNA modifications following C. parvum injection into the DRG.
- To investigate the role of macrophages in sensory neuron responses to nerve injury and regeneration.
Main Methods:
- In situ hybridization was used to analyze neuronal mRNA levels.
- Specific mRNAs investigated included growth-associated protein (GAP-43), c-jun, and calcitonin gene-related peptide (CGRP).
Main Results:
- Neuronal concentrations of GAP-43 and c-jun mRNAs increased after C. parvum injection, similar to axotomy responses.
- Calcitonin gene-related peptide (CGRP) mRNA levels increased in a subpopulation of sensory neurons post-injection, contrasting with its decrease after axotomy.
Conclusions:
- The findings support the hypothesis that macrophages accumulating in the DRG after nerve injury sustain sensory neuron responses.
- Macrophages may play a crucial role in promoting nerve regeneration by modulating gene expression in sensory neurons.