Basic NeuroscienceA novel technique for morphometric quantification of subarachnoid hemorrhage-induced microglia activation

- Development of a novel morphometric analysis to quantify microglia activation following SAH.
- This analysis revealed a decrease in microglial process complexity 2 and 7 days following SAH.
- Further, this analysis demonstrated an increase in microglial domain volume 1 day following SAH.
- This work represents advancement in glial cell morphometric quantification capabilities.
- These tools increase understanding of the time course and degree of microglia activation after SAH.

BackgroundSubarachnoid hemorrhage (SAH) is a neurologic catastrophe and poor outcome is typically attributed to vasospasm; however, there is also evidence that SAH causes a pro-inflammatory state and these two phenomena may be interrelated. SAH causes activation of microglia, but the time course and degree of microglial activation after SAH and its link to poor patient outcome and vasospasm remains unknown.New methodTransgenic mice expressing eGFP under the control of the CX3CR1 locus, in which microglia are endogenously fluorescent, were randomly assigned to control or SAH groups. Immunohistochemistry for CD-68 and CD-31 was performed at different time points after SAH. Using confocal microscopy and MatLab software, we have developed a novel technique to detect and quantify the stages of microglial activation and return to quiescence using an automated computerized morphometric analysis.ResultsWe detected a statistically significant decrease in microglial process complexity 2 and 7 days following SAH. In addition, we detected a statistically significant increase in microglial domain volume 1 day following SAH; however, microglial domain volume returned to baseline by 2 days.Comparison with existing methodMost techniques for microglia assessment are qualitative, not quantitative, and are therefore inadequate to address the effects of anti-inflammatory drug treatment or other therapies after SAH.ConclusionsUsing novel image analysis techniques we were able to reproducibly quantify activation of microglia following SAH, which will improve our ability to study the biology of microglial activation, and may ultimately improve management of disease progression and response to therapies directed at microglial activation.