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Developmental stage of oligodendrocytes determines their response to activated microglia in vitro.

Miller BA, Crum JM, Tovar CA, Ferguson AR, Bresnahan JC, Beattie MS - J Neuroinflammation (2007)

Bottom Line: Lipopolysaccharide was used to activate microglia and microglial activation was confirmed by TNFalpha ELISA.Activated microglia reduced OPC survival, but increased survival and reduced apoptosis of mature oligodendrocytes.Activated microglia may have divergent effects on OPCs and mature oligodendrocytes, reducing OPC survival and increasing mature oligodendrocyte survival.

View Article: PubMed Central - HTML - PubMed

Affiliation: Brain and Spinal Injury Center, Department of Neurological Surgery, University of California San Francisco, 1001 Potrero Ave, Building 1, Room 101, San Francisco, CA 94143, USA. Brandon.Miller@osumc.edu

ABSTRACT

Background: Oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes are both lost in central nervous system injury and disease. Activated microglia may play a role in OPC and oligodendrocyte loss or replacement, but it is not clear how the responses of OPCs and oligodendrocytes to activated microglia differ.

Methods: OPCs and microglia were isolated from rat cortex. OPCs were induced to differentiate into oligodendrocytes with thyroid hormone in defined medium. For selected experiments, microglia were added to OPC or oligodendrocyte cultures. Lipopolysaccharide was used to activate microglia and microglial activation was confirmed by TNFalpha ELISA. Cell survival was assessed with immunocytochemistry and cell counts. OPC proliferation and oligodendrocyte apoptosis were also assessed.

Results: OPCs and oligodendrocytes displayed phenotypes representative of immature and mature oligodendrocytes, respectively. Activated microglia reduced OPC survival, but increased survival and reduced apoptosis of mature oligodendrocytes. Activated microglia also underwent cell death themselves.

Conclusion: Activated microglia may have divergent effects on OPCs and mature oligodendrocytes, reducing OPC survival and increasing mature oligodendrocyte survival. This may be of importance because activated microglia are present in several disease states where both OPCs and mature oligodendrocytes are also reacting to injury. Activated microglia may simultaneously have deleterious and helpful effects on different cells after central nervous system injury.

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Related in: MedlinePlus

Microglia and LPS-activated microglia both increase oligodendrocyte survival. Oligodendrocytes were cultured in combination with microglia (A). Dead oligodendrocytes were visible by cellular debris left behind after fixation and staining (B) and therefore oligodendrocyte cell death was quantified as percent cell death based on cell counts. Both microglia and microglia activated by LPS significantly reduced the percentage of dead oligodendrocytes (C, * = p < 0.05, factorial ANOVA for main effect of microglia, error bars = SEM). The protective effect of microglia was unchanged by the presence of LPS (p < 0.05 factorial ANOVA).
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Figure 6: Microglia and LPS-activated microglia both increase oligodendrocyte survival. Oligodendrocytes were cultured in combination with microglia (A). Dead oligodendrocytes were visible by cellular debris left behind after fixation and staining (B) and therefore oligodendrocyte cell death was quantified as percent cell death based on cell counts. Both microglia and microglia activated by LPS significantly reduced the percentage of dead oligodendrocytes (C, * = p < 0.05, factorial ANOVA for main effect of microglia, error bars = SEM). The protective effect of microglia was unchanged by the presence of LPS (p < 0.05 factorial ANOVA).

Mentions: For these experiments, pure oligodendrocyte cultures, with and without microglia added, were utilized (Fig. 6A). Oligodendrocyte death was quantified as percent dead out of total since remains of individual dead oligodendrocytes were still clearly visible after fixation and staining (Fig. 6B). As with OPCs, there was no main effect of 10 ng/ml LPS alone on oligodendrocyte survival. However, there was a main effect of microglia on oligodendrocyte survival (Fig. 6C, p < 0.001, factorial ANOVA). In the presence of microglia, oligodendrocyte death was significantly decreased to 33 ± 8% from control values of 56 ± 10% (p = 0.013, ANOVA, Tukey's post-hoc), and in the presence of microglia and LPS, oligodendrocyte death was significantly reduced to 28 ± 9% (p = 0.004, ANOVA, Tukey's post-hoc). Analysis of total number (live + dead) oligodendrocytes revealed no effect of treatment group on total oligodendrocyte number, verifying that microglia did not alter oligodendrocyte attachment to the culture substrate (data not shown).


Developmental stage of oligodendrocytes determines their response to activated microglia in vitro.

Miller BA, Crum JM, Tovar CA, Ferguson AR, Bresnahan JC, Beattie MS - J Neuroinflammation (2007)

Microglia and LPS-activated microglia both increase oligodendrocyte survival. Oligodendrocytes were cultured in combination with microglia (A). Dead oligodendrocytes were visible by cellular debris left behind after fixation and staining (B) and therefore oligodendrocyte cell death was quantified as percent cell death based on cell counts. Both microglia and microglia activated by LPS significantly reduced the percentage of dead oligodendrocytes (C, * = p < 0.05, factorial ANOVA for main effect of microglia, error bars = SEM). The protective effect of microglia was unchanged by the presence of LPS (p < 0.05 factorial ANOVA).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2214724&req=5

Figure 6: Microglia and LPS-activated microglia both increase oligodendrocyte survival. Oligodendrocytes were cultured in combination with microglia (A). Dead oligodendrocytes were visible by cellular debris left behind after fixation and staining (B) and therefore oligodendrocyte cell death was quantified as percent cell death based on cell counts. Both microglia and microglia activated by LPS significantly reduced the percentage of dead oligodendrocytes (C, * = p < 0.05, factorial ANOVA for main effect of microglia, error bars = SEM). The protective effect of microglia was unchanged by the presence of LPS (p < 0.05 factorial ANOVA).
Mentions: For these experiments, pure oligodendrocyte cultures, with and without microglia added, were utilized (Fig. 6A). Oligodendrocyte death was quantified as percent dead out of total since remains of individual dead oligodendrocytes were still clearly visible after fixation and staining (Fig. 6B). As with OPCs, there was no main effect of 10 ng/ml LPS alone on oligodendrocyte survival. However, there was a main effect of microglia on oligodendrocyte survival (Fig. 6C, p < 0.001, factorial ANOVA). In the presence of microglia, oligodendrocyte death was significantly decreased to 33 ± 8% from control values of 56 ± 10% (p = 0.013, ANOVA, Tukey's post-hoc), and in the presence of microglia and LPS, oligodendrocyte death was significantly reduced to 28 ± 9% (p = 0.004, ANOVA, Tukey's post-hoc). Analysis of total number (live + dead) oligodendrocytes revealed no effect of treatment group on total oligodendrocyte number, verifying that microglia did not alter oligodendrocyte attachment to the culture substrate (data not shown).

Bottom Line: Lipopolysaccharide was used to activate microglia and microglial activation was confirmed by TNFalpha ELISA.Activated microglia reduced OPC survival, but increased survival and reduced apoptosis of mature oligodendrocytes.Activated microglia may have divergent effects on OPCs and mature oligodendrocytes, reducing OPC survival and increasing mature oligodendrocyte survival.

View Article: PubMed Central - HTML - PubMed

Affiliation: Brain and Spinal Injury Center, Department of Neurological Surgery, University of California San Francisco, 1001 Potrero Ave, Building 1, Room 101, San Francisco, CA 94143, USA. Brandon.Miller@osumc.edu

ABSTRACT

Background: Oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes are both lost in central nervous system injury and disease. Activated microglia may play a role in OPC and oligodendrocyte loss or replacement, but it is not clear how the responses of OPCs and oligodendrocytes to activated microglia differ.

Methods: OPCs and microglia were isolated from rat cortex. OPCs were induced to differentiate into oligodendrocytes with thyroid hormone in defined medium. For selected experiments, microglia were added to OPC or oligodendrocyte cultures. Lipopolysaccharide was used to activate microglia and microglial activation was confirmed by TNFalpha ELISA. Cell survival was assessed with immunocytochemistry and cell counts. OPC proliferation and oligodendrocyte apoptosis were also assessed.

Results: OPCs and oligodendrocytes displayed phenotypes representative of immature and mature oligodendrocytes, respectively. Activated microglia reduced OPC survival, but increased survival and reduced apoptosis of mature oligodendrocytes. Activated microglia also underwent cell death themselves.

Conclusion: Activated microglia may have divergent effects on OPCs and mature oligodendrocytes, reducing OPC survival and increasing mature oligodendrocyte survival. This may be of importance because activated microglia are present in several disease states where both OPCs and mature oligodendrocytes are also reacting to injury. Activated microglia may simultaneously have deleterious and helpful effects on different cells after central nervous system injury.

Show MeSH
Related in: MedlinePlus