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Microglia responses in the CNS following sciatic nerve transection in C57BL/Wld(s) and BALB/c mice
1Department of Anatomy, Faculty of Medicine, National University of Singapore.
Abstract:
The present study employed C57BL/Wld(s) mice to investigate whether a delay in microglia reaction would occur similar to the delay that occurs in macrophage response after sciatic neurectomy. The results were compared with control BALB/c mice. The observations showed that in both strains of mice there was no delayed microglia response around lesioned motoneurons and around the central processes of the dorsal root ganglion cells after sciatic neurectomy in the adult. The increased Mac-1 staining appeared as early as 1 day postoperation (dpo). This indicates that microglial cells and macrophages respond to different signals generated by neurectomy. In both strains of mice, the number of microglia in the neonate was much less than that in the adult and the increase in Mac-1 staining was detectable only at 3 dpo in both strains of mice. A significant loss of motoneurons was detected after sciatic neurectomy in the neonate. However, there were no significant differences in the mean percentages of motoneuron loss between the two strains of mice at 5, 10, and 15 dpo. It is surmised that the lack of an adequate number of mature microglia in the neonates and their tardy expression of CR3 antigenicity may contribute to the motoneuron loss.
Insights
In adult mice, microglia and macrophages react quickly to sciatic nerve injury. However, neonates show delayed microglial response and increased motoneuron loss, suggesting immature microglia contribute to this loss.
Area of Science:
- Neuroscience
- Immunology
- Developmental Biology
Background:
- Macrophages exhibit a delayed response following sciatic neurectomy.
- Microglia are the resident immune cells in the central nervous system.
Purpose of the Study:
- To investigate if microglia exhibit a delayed response post-sciatic neurectomy, similar to macrophages.
- To compare microglial responses in adult and neonatal mice after sciatic neurectomy.
- To assess the impact of microglial response on motoneuron survival.
Main Methods:
- Sciatic neurectomy was performed on C57BL/Wld(s) and BALB/c mice (adult and neonate).
- Mac-1 staining was used to assess microglial and macrophage activation.
- Motoneuron loss was quantified at 5, 10, and 15 days postoperation.
Main Results:
- Adult mice showed no delay in microglial response (Mac-1 staining at 1 day postoperation).
- Neonatal mice displayed a delayed microglial response (Mac-1 staining at 3 days postoperation) and significant motoneuron loss.
- No significant difference in motoneuron loss was observed between the two strains in neonates.
Conclusions:
- Microglia and macrophages respond to different signals after sciatic neurectomy.
- The delayed microglial response and lower cell numbers in neonates may contribute to increased motoneuron loss.
- Immature microglia may impair neuroprotective mechanisms in neonatal nerve injury.