Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Apr 17:1266:29-36.
doi: 10.1016/j.brainres.2009.02.031. Epub 2009 Feb 26.

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

Lee A Shapiro  1 , Zachary D Perez, Maira L Foresti, Gabriel M Arisi, Charles E Ribak
Affiliations

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

Lee A Shapiro et al. Brain Res. .

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 complexes. 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 mum 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.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
Confocal Z-stack merged images depicting Iba1-immunolabeled cells and Neu-N labeled neurons found in the dentate gyrus. A depicts Iba1-immunolabeled cells located at the border of the hilus and granule cell layer (GL), in the molecular layer (ML) and in the hilus. Note the relatively even spacing and uniform distribution between the Iba1-immunolabeled cell bodies in the hilus. Many Iba1-labeled cells are concentrated at the border between the hilus and GL, i.e., the subgranular zone (arrows). Other cells with processes extending into the granule cell layer have their cell bodies (arrowhead) in the ML. Iba1-labeled cells in the GL (red arrows) are relatively infrequent. B shows both Iba1-immunolabeled cells and Neu-N labeled neuronal somata located within the dentate gyrus. The hilar region was traced (red line) in order to determine the frequency of Iba1-immunolabeled cell bodies apposed to Neu-N neuronal somata, and examples of this apposition are indicated (white arrows). Scale bar = 20 μm for A and B.
Fig. 2
Fig. 2
Electron micrographs of microglial cell bodies found in the hilus of the dentate gyrus. A shows a peri-neuronal Iba1-labeled cell body, with the Nissl body (large arrow) of a nearby neuron (N) located close to this microglial cell’s plasma membrane. B is an enlargement of the microglial cell body. Note the inclusion bodies (asterisks) and a prominent centrosome (white arrow) within its perikaryon. In C, a dark band of Iba1 immunoreaction product (white arrows) is observed surrounding the cell nucleus (N) of another microglial cell. Most of the dense heterochromatin within the nucleus is found near the nuclear envelope. Two Iba1-labeled profiles (black arrows) appear in the neuropil. D is an Iba1-labeled cell body with a boot-shaped nucleus (N), a triangular-shaped cell body, and multiple inclusion bodies (asterisks). Scale bars = 2 μm for A and 1 μm for B–D.
Fig. 3
Fig. 3
Electron micrographs of a peri-neuronal Iba1-labeled microglial cell found in the hilus of the dentate gyrus. A shows the nucleus (N) of this Iba1-labeled microglial cell that apposes a neuronal cell body (CB). Note that the immuno-reaction product is limited to the perikaryal cytoplasm of the microglial cell and its electron density is increased at the site of apposition to the neuronal cell body. Some of the cellular organelles observed within the neuronal cell body include the Golgi apparatus (G) and granular endoplasmic reticulum (ER). B is an enlargement of the same Iba1-labeled microglial cell and neuronal cell body found in A. Note the typical chromatin pattern for the nucleus (N) of this microglial cell with heterochromatin mainly concentrated adjacent to the nuclear envelope. C is an enlargement of the box in B. Thin astrocytic processes (open arrows) separate small portions of the apposition between the microglial cell and the neuronal cell body while a direct apposition is found at just one site (large arrow). Several postsynaptic densities (arrowheads) are found in the neuronal cell body at this apposition while others are involved in a synapse with an axon terminal (T). Several exosomes (small arrows) are located in the extracellular space surrounding the Iba1-labeled microglial cell body. Scale bars = 2 μm for A and 0.5 μm for B and C.
Fig. 4
Fig. 4
Electron micrographs of peri-capillary Iba1-labeled microglial cell bodies found in the hilus. A shows an Iba1-labeled microglial cell body near a blood vessel (V) with its characteristic nucleus (N) and immunoreaction product (white arrows) in its perikaryal cytoplasm. Note the myelinated axons (M) in the adjacent neuropil. B is an enlargement of an adjacent serial section showing the peri-capillary cell found in A. One of the myelinated axons (M) is shown as well as the immunoreaction product (white arrows). The microglial cell’s plasma membrane and the basal lamina of the endothelial cell lining this capillary (V) are only separated by about 0.5 μm. C demonstrates another example of a peri-capillary, Iba1-labeled cell body with the typical morphology of its nucleus (N). Also, this cell’s plasma membrane and the basal lamina of the endothelial cell are separated by only 0.16 μm. Scale bars = 1 μm for A and 0.5 μm for B and C.
Fig. 5
Fig. 5
Electron micrographs of an Iba1-labeled microglial cell body with a labeled process found in the adjacent neuropil. A shows the labeled cell body and a few inclusion bodies (asterisks) found within its cytoplasm. The proximal part of its process (arrows) is shown in A while panel B shows a more distal portion of this process. Note that this Iba1-labeled process (arrows) extends into the neuropil where several myelinated axons (M) are found. A pedunculated side branch (arrowheads) arises from this labeled process. Scale bars = 1 μm for A and B.
Fig. 6
Fig. 6
Electron micrographs of an Iba1-labeled microglial cell with Iba1-labeled processes in the hilus of the dentate gyrus. A shows an Iba1-labeled cell body with four cross-sectioned Iba1-labeled processes found approximately 4.6 μm (P4) and 11 μm (P1-P3) away from the cell’s nucleus (N). Mossy fibers (arrows) can also be seen scattered throughout the neuropil. B is an enlargement of the Iba1-labeled cell found in A and shows an inclusion body (asterisk) located its perikaryon. One of the Iba1-labeled processes (P4) is also shown. C is an enlargement of the three cross-sectioned Iba1-labeled processes (P1–P3). Note the arrangement of the cross-sectioned processes, demonstrating what appears to be a central process (P2) with two side branches (P1, P3). Scale bars = 2 μm for A–C.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Aarum J, Sandberg K, Haeberlein SL, Persson MA. Migration and differentiation of neural precursor cells can be directed by microglia. Proc Natl Acad Sci U S A. 2003;100:15983–15988. - PMC - PubMed
    1. Batchelor PE, Liberatore GT, Wong JYF, Porritt MJ, Frerichs F, Donnan JA, Howells DW. Activated macrophages and microglia induce dopaminergic sprouting in the injured striatum and express brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor. J Neurosci. 1999;19:1708–1716. - PMC - PubMed
    1. Biber K, Neumann H, Inoue K, Boddeke HW. Neuronal ‘On’ and ‘Off’ signals control microglia. Trends Neurosci. 2007;30:596–602. - PubMed
    1. Borges K, Gearing M, McDermott DL, Smith AB, Almonte AG, Wainer BH, Dingledine R. Neuronal and glial pathological changes during epileptogenesis in the mouse pilocarpine model. Exp Neurol. 2003;182:21–34. - PubMed
    1. Chen S, Pickard JD, Harris NG. Time course of cellular pathology after controlled cortical impact injury. Exp Neurol. 2003;182:87–102. - PubMed

Publication types

MeSH terms