Background: Microglia are long-lived cells that constantly monitor their
microenvironment. To accomplish this task, they constantly change their morphology both in the short and long term under physiological conditions. This
makes the process of quantifying physiological microglial morphology difficult.
Results: By using a semi-manual and a semi-automatic method to assess fine
changes in cortical microglia morphology, we were able to quantify microglia
changes in number, surveillance and branch tree starting from the fifth postnatal day to 2 years of life. We were able to identify a fluctuating behavior of most
analyzed parameters characterized by a rapid cellular maturation, followed by
a long period of relative stable morphology during the adult life with a final
convergence to an aged phenotype. Detailed cellular arborization analysis
revealed age-induced differences in microglia morphology, with mean branch
length and the number of terminal processes changing constantly over time.
Conclusions: Our study provides insight into microglia morphology changes
across lifespan under physiological conditions. We were able to highlight, that
due to the dynamic nature of microglia several morphological parameters are
needed to establish the physiological state of these cells