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Formation of multinucleated giant cells and microglial degeneration in rats expressing a mutant Cu/Zn superoxide dismutase gene.

Fendrick SE, Xue QS, Streit WJ - J Neuroinflammation (2007)

Bottom Line: In animals during end stage disease at 4-5 months of age virtually all microglia in the spinal cord gray matter showed extensive fragmentation of their cytoplasm (cytorrhexis), indicative of widespread microglial degeneration.Few microglia exhibiting nuclear fragmentation (karyorrhexis) indicative of apoptosis were identified at any stage.The current findings demonstrate the occurrence of severe abnormalities in microglia, such as cell fusions and cytorrhexis, which may be the result of expression of mutant SOD1 in these cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience, University of Florida College of Medicine and McKnight Brain Institute, Gainesville, FL 32611, USA. sefendrick@yahoo.com

ABSTRACT

Background: Microglial neuroinflammation is thought to play a role in the pathogenesis of amyotrophic lateral sclerosis (ALS). The purpose of this study was to provide a histopathological evaluation of the microglial neuroinflammatory response in a rodent model of ALS, the SOD1G93A transgenic rat.

Methods: Multiple levels of the CNS from spinal cord to cerebral cortex were studied in SOD1G93A transgenic rats during three stages of natural disease progression, including presymptomatic, early symptomatic (onset), and late symptomatic (end stage), using immuno- and lectin histochemical markers for microglia, such as OX-42, OX-6, and Griffonia simplicifolia isolectin B4.

Results: Our studies revealed abnormal aggregates of microglia forming in the spinal cord as early as the presymptomatic stage. During the symptomatic stages there was prominent formation of multinucleated giant cells through fusion of microglial cells in the spinal cord, brainstem, and red nucleus of the midbrain. Other brain regions, including substantia nigra, cranial nerve nuclei, hippocampus and cortex showed normal appearing microglia. In animals during end stage disease at 4-5 months of age virtually all microglia in the spinal cord gray matter showed extensive fragmentation of their cytoplasm (cytorrhexis), indicative of widespread microglial degeneration. Few microglia exhibiting nuclear fragmentation (karyorrhexis) indicative of apoptosis were identified at any stage.

Conclusion: The current findings demonstrate the occurrence of severe abnormalities in microglia, such as cell fusions and cytorrhexis, which may be the result of expression of mutant SOD1 in these cells. The microglial changes observed are different from those that accompany normal microglial activation, and they demonstrate that aberrant activation and degeneration of microglia is part of the pathogenesis of motor neuron disease.

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Microglial staining with OX-42 immunohistochemistry in the spinal cord during three different stages of motor neuron disease progression. A, presymptomatic stage; inset shows early microglial fusion in spinal cord. B, disease onset; C, end stage; D, wild type control. Note the dramatic increase in microglial staining with OX-42 during onset (B) and its subsequent decline during end stage (C). Scale bar: 200 μm. E, morphometric quantification of microglial immunostaining with OX-42 during disease development; * p < 0.05 and ** p < 0.001 with respect to age-matched controls; # p < 0.05 with respect to onset group.
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Figure 1: Microglial staining with OX-42 immunohistochemistry in the spinal cord during three different stages of motor neuron disease progression. A, presymptomatic stage; inset shows early microglial fusion in spinal cord. B, disease onset; C, end stage; D, wild type control. Note the dramatic increase in microglial staining with OX-42 during onset (B) and its subsequent decline during end stage (C). Scale bar: 200 μm. E, morphometric quantification of microglial immunostaining with OX-42 during disease development; * p < 0.05 and ** p < 0.001 with respect to age-matched controls; # p < 0.05 with respect to onset group.

Mentions: The CR3 complement receptor recognized by OX-42 antibody is expressed constitutively by all resting and activated microglial cells [21]. OX-42 immunoreactivity observed in presymptomatic SOD1 transgenic rats was similar to that seen in wild type control, i.e. there was uniform staining of all resting microglia (Figs. 1A,D). Occasionally, in these presymptomatic animals cell fusions involving several microglia were observed (Fig. 1A, inset). The onset of symptoms was associated with a dramatic increase in OX-42 staining in the ventral horn due to much greater microglial cell numbers (Fig. 1B). Many of these seemingly activated microglia were clustered and/or fused into multi-cellular aggregates. In end stage animals, overall immunoreactivity with OX-42 was decreased compared to that seen in animals with disease onset (Fig. 1C). This unexpected diminution in microglial staining was due to widespread degenerative cytoplasmic fragmentation affecting most, if not all microglia within the ventral horn (see below). The qualitatively evident increases and decreases in immunoreactivity were confirmed through quantitative morphometric measurements (Fig. 1E).


Formation of multinucleated giant cells and microglial degeneration in rats expressing a mutant Cu/Zn superoxide dismutase gene.

Fendrick SE, Xue QS, Streit WJ - J Neuroinflammation (2007)

Microglial staining with OX-42 immunohistochemistry in the spinal cord during three different stages of motor neuron disease progression. A, presymptomatic stage; inset shows early microglial fusion in spinal cord. B, disease onset; C, end stage; D, wild type control. Note the dramatic increase in microglial staining with OX-42 during onset (B) and its subsequent decline during end stage (C). Scale bar: 200 μm. E, morphometric quantification of microglial immunostaining with OX-42 during disease development; * p < 0.05 and ** p < 0.001 with respect to age-matched controls; # p < 0.05 with respect to onset group.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808448&req=5

Figure 1: Microglial staining with OX-42 immunohistochemistry in the spinal cord during three different stages of motor neuron disease progression. A, presymptomatic stage; inset shows early microglial fusion in spinal cord. B, disease onset; C, end stage; D, wild type control. Note the dramatic increase in microglial staining with OX-42 during onset (B) and its subsequent decline during end stage (C). Scale bar: 200 μm. E, morphometric quantification of microglial immunostaining with OX-42 during disease development; * p < 0.05 and ** p < 0.001 with respect to age-matched controls; # p < 0.05 with respect to onset group.
Mentions: The CR3 complement receptor recognized by OX-42 antibody is expressed constitutively by all resting and activated microglial cells [21]. OX-42 immunoreactivity observed in presymptomatic SOD1 transgenic rats was similar to that seen in wild type control, i.e. there was uniform staining of all resting microglia (Figs. 1A,D). Occasionally, in these presymptomatic animals cell fusions involving several microglia were observed (Fig. 1A, inset). The onset of symptoms was associated with a dramatic increase in OX-42 staining in the ventral horn due to much greater microglial cell numbers (Fig. 1B). Many of these seemingly activated microglia were clustered and/or fused into multi-cellular aggregates. In end stage animals, overall immunoreactivity with OX-42 was decreased compared to that seen in animals with disease onset (Fig. 1C). This unexpected diminution in microglial staining was due to widespread degenerative cytoplasmic fragmentation affecting most, if not all microglia within the ventral horn (see below). The qualitatively evident increases and decreases in immunoreactivity were confirmed through quantitative morphometric measurements (Fig. 1E).

Bottom Line: In animals during end stage disease at 4-5 months of age virtually all microglia in the spinal cord gray matter showed extensive fragmentation of their cytoplasm (cytorrhexis), indicative of widespread microglial degeneration.Few microglia exhibiting nuclear fragmentation (karyorrhexis) indicative of apoptosis were identified at any stage.The current findings demonstrate the occurrence of severe abnormalities in microglia, such as cell fusions and cytorrhexis, which may be the result of expression of mutant SOD1 in these cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroscience, University of Florida College of Medicine and McKnight Brain Institute, Gainesville, FL 32611, USA. sefendrick@yahoo.com

ABSTRACT

Background: Microglial neuroinflammation is thought to play a role in the pathogenesis of amyotrophic lateral sclerosis (ALS). The purpose of this study was to provide a histopathological evaluation of the microglial neuroinflammatory response in a rodent model of ALS, the SOD1G93A transgenic rat.

Methods: Multiple levels of the CNS from spinal cord to cerebral cortex were studied in SOD1G93A transgenic rats during three stages of natural disease progression, including presymptomatic, early symptomatic (onset), and late symptomatic (end stage), using immuno- and lectin histochemical markers for microglia, such as OX-42, OX-6, and Griffonia simplicifolia isolectin B4.

Results: Our studies revealed abnormal aggregates of microglia forming in the spinal cord as early as the presymptomatic stage. During the symptomatic stages there was prominent formation of multinucleated giant cells through fusion of microglial cells in the spinal cord, brainstem, and red nucleus of the midbrain. Other brain regions, including substantia nigra, cranial nerve nuclei, hippocampus and cortex showed normal appearing microglia. In animals during end stage disease at 4-5 months of age virtually all microglia in the spinal cord gray matter showed extensive fragmentation of their cytoplasm (cytorrhexis), indicative of widespread microglial degeneration. Few microglia exhibiting nuclear fragmentation (karyorrhexis) indicative of apoptosis were identified at any stage.

Conclusion: The current findings demonstrate the occurrence of severe abnormalities in microglia, such as cell fusions and cytorrhexis, which may be the result of expression of mutant SOD1 in these cells. The microglial changes observed are different from those that accompany normal microglial activation, and they demonstrate that aberrant activation and degeneration of microglia is part of the pathogenesis of motor neuron disease.

Show MeSH
Related in: MedlinePlus