Morphological and ultrastructural features of Iba1-immunolabeled microglial cells in the hippocampal dentate gyrus

Abstract

Microglia are found throughout the central nervous system, respond rapidly to pathology and are involved in several components of the neuroinflammatory response. Iba1 is a marker for microglial cells and previous immunocytochemical studies have utilized this and other microglial-specific antibodies to demonstrate the morphological features of microglial cells at the light microscopic level. However, there is a paucity of studies that have used microglial-specific antibodies to describe the ultrastructural features of microglial cells and their processes. The goal of the present study is to use Iba1 immuno-electron microscopy to elucidate the fine structural features of microglial cells and their processes in the hilar region of the dentate gyrus of adult Sprague-Dawley rats. Iba1-labeled cell bodies were observed adjacent to neurons and capillaries, as well as dispersed in the neuropil. The nuclei of these cells had dense heterochromatin next to the nuclear envelope and lighter chromatin in their center. Iba1-immunolabeling was found within the thin shell of perikaryal cytoplasm that contained the usual organelles, including mitochondria, cisternae of endoplasmic reticulum and Golgi complex. Iba1-labeled cell bodies also commonly displayed an inclusion body. Iba1-labeled cell bodies gave rise to processes that often had a small side branch arise within 5 μm of the microglial cell body. These data showing “resting” Iba-1 labeled microglial cells in the normal adult rat dentate gyrus provide a basis for comparison with the morphology of microglial cells in disease and injury models where they are activated or phagocytotic.

Influence of the vanilloid receptor TRPV1 on the activation of spinal cord glia in mouse models of pain

“…The observed changes in morphology of glia, from the “quiescent” phenotype in naïve mice to the “reactive” phenotype in treated mice, were consistent with the activated state of glia (Shapiro et al, 2009). The majority of the Iba1-positive cells in the dorsal horn that displayed this changed morphology also expressed the activated form of p38 MAP kinase and the GFAP-positive cells expressed the activated form of c-Jun-Activated Kinase (JNK), as revealed by a double immunofluorescence using phospho-specific antibodies (Han, Willcockson and Valtschanoff, unpublished observations), providing independent evidence for activation of microglia (Ji and Suter, 2007; Tsuda et al, 2005).…”

Microglial Interactions with Synapses Are Modulated by Visual Experience

“…Building on previous EM observations that microglia contact axon terminals and dendritic spines [9],[44],[45], our quantitative analysis revealed that most microglial processes directly appose not only axon terminals and dendritic spines, but also perisynaptic astrocytic processes and synaptic clefts. Our SSEM with 3-D reconstructions also uncovered the 3-D relationships between microglia and synapses, revealing that microglial processes contact multiple synapse-associated elements at multiple synapses simultaneously.…”

Accelerated microglial pathology is associated with Aβ plaques in mouse models of Alzheimer's disease

“…As IbaI is commonly used for morphometric and ultrastructural analyses of microglia (Shapiro et al ., 2009), we performed the same morphological analysis in brain sections immunolabeled with anti-IbaI (Fig. S1).…”