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Persistent inflammation alters the function of the endogenous brain stem cell compartment.

Pluchino S, Muzio L, Imitola J, Deleidi M, Alfaro-Cervello C, Salani G, Porcheri C, Brambilla E, Cavasinni F, Bergamaschi A, Garcia-Verdugo JM, Comi G, Khoury SJ, Martino G - Brain (2008)

Bottom Line: Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke), the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized.Here we show that persistent brain inflammation, induced by immune cells targeting myelin, extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche.Together, these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders.

View Article: PubMed Central - PubMed

Affiliation: Neuroimmunology Unit, DIBIT, San Raffaele Scientific Institute, Milano, Italy.

ABSTRACT
Endogenous neural stem/precursor cells (NPCs) are considered a functional reservoir for promoting tissue homeostasis and repair after injury, therefore regenerative strategies that mobilize these cells have recently been proposed. Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke), the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized. Here we show that persistent brain inflammation, induced by immune cells targeting myelin, extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche. In parallel, we demonstrate a quantitative reduction of the putative brain stem cells proliferation in the SVZ during persistent brain inflammation, which is completely reversed after in vitro culture of the isolated NPCs. Together, these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders.

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Chronic autoimmune CNS inflammation impairs proliferation of SVZ-resident NPCs in vivo. (A) Decrease of M-phase confined phosphorylated histone H3 (pH3)+ cells is observed in the SVZ of EAE mice at both 20, 30 and 60 dpi. Data in the graph are represented as mean numbers of pH3-immunoreactive cells/section ± SEM and have been obtained from a total of n ≥ 5 mice per group. *P ≤ 0.05, when compared with HC. Two representative images of pH3+ cells in the SVZ of HC and EAE 30 dpi are shown. Scale bars 50 μm. (B–E) Coronal sections of the dorsolateral SVZ from HC mice (B and D) and mice with EAE at 30 dpi (C and E) showing fast-proliferating IddU+ cells (green in B and C), IddU+/Iba1+ (green and red in B and C, respectively) and CD45+/Ki67+ (green and red in D and E, respectively) cells in EAE vs. HC. Arrowheads indicate Iddu–/Iba1+ cells in both panels. Scale bars: 50 μm. (F) Decrease of long-term BrdU-retaining cells is observed in the SVZ of EAE mice at 30 dpi. Mice received BrdU for 6 days starting from either 13 or 30 dpi and were sacrificed 40 days after the last BrdU injection. Data are represented as mean numbers of BrdU+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group from n ≥ 2 independent experiments. *P ≤ 0.001, when compared with HC. Two representative confocal microscopy pictures showing long term-retaining BrdU+ (red) GFAP+ (green) cells from the SVZ of HC and EAE 30 dpi are shown. (G) Decrease of SVZ cells expressing the mRNA for PDGFrα is observed in the SVZ of EAE mice at 20 dpi. PdgfRα mRNA is expressed by putative type slow-dividing cells located within the SVZ, as well as by OPCs that are widely distributed within the adult brain parenchyma (arrowheads in the upper panel). Data are represented as mean numbers of PDGFrα+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group. Scale bars: 50 μm. Nuclei in (B–G) have been counterstained with DAPI. LV, lateral ventricle.
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Figure 1: Chronic autoimmune CNS inflammation impairs proliferation of SVZ-resident NPCs in vivo. (A) Decrease of M-phase confined phosphorylated histone H3 (pH3)+ cells is observed in the SVZ of EAE mice at both 20, 30 and 60 dpi. Data in the graph are represented as mean numbers of pH3-immunoreactive cells/section ± SEM and have been obtained from a total of n ≥ 5 mice per group. *P ≤ 0.05, when compared with HC. Two representative images of pH3+ cells in the SVZ of HC and EAE 30 dpi are shown. Scale bars 50 μm. (B–E) Coronal sections of the dorsolateral SVZ from HC mice (B and D) and mice with EAE at 30 dpi (C and E) showing fast-proliferating IddU+ cells (green in B and C), IddU+/Iba1+ (green and red in B and C, respectively) and CD45+/Ki67+ (green and red in D and E, respectively) cells in EAE vs. HC. Arrowheads indicate Iddu–/Iba1+ cells in both panels. Scale bars: 50 μm. (F) Decrease of long-term BrdU-retaining cells is observed in the SVZ of EAE mice at 30 dpi. Mice received BrdU for 6 days starting from either 13 or 30 dpi and were sacrificed 40 days after the last BrdU injection. Data are represented as mean numbers of BrdU+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group from n ≥ 2 independent experiments. *P ≤ 0.001, when compared with HC. Two representative confocal microscopy pictures showing long term-retaining BrdU+ (red) GFAP+ (green) cells from the SVZ of HC and EAE 30 dpi are shown. (G) Decrease of SVZ cells expressing the mRNA for PDGFrα is observed in the SVZ of EAE mice at 20 dpi. PdgfRα mRNA is expressed by putative type slow-dividing cells located within the SVZ, as well as by OPCs that are widely distributed within the adult brain parenchyma (arrowheads in the upper panel). Data are represented as mean numbers of PDGFrα+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group. Scale bars: 50 μm. Nuclei in (B–G) have been counterstained with DAPI. LV, lateral ventricle.

Mentions: To study the rapidly dividing transit-amplifying progenitor cells (type C cells) we used short-term IddU labelling protocols (see Supplementary data). We did not find any significant difference in the cell cycle length (Tc) in the SVZ of EAE versus HC mice (Table 1). On the other hand, the GF of EAE mice at 20 and 30 dpi was significantly lower compared with HC (both P ≤ 0.05), though a return toward baseline values was observed between 60 and 90 dpi (Table 1). Accordingly, a significant reduction in the absolute numbers of M-phase-confined phosphorylated histone H3 (pH3)+ SVZ cells was observed in EAE mice at 20, 30 and 60 dpi (Figure 1A) when compared with HC (all P ≤ 0.05). Again, a return toward baseline values in the numbers of pH3+ cells was observed in EAE at 90 dpi (data not shown). Finally, few—if any—IddU+/Iba1+ and/or CD45+/Ki67+ cells were found within the SVZ of EAE mice (Figure 1B–E), thus suggesting that the proliferation of either local microglial cells or CNS-infiltrating blood-derived leucocytes did not contribute significantly to the total GF quantified within the dorso-lateral SVZ. Apoptosis of neural cells could not account for the observed decreased GF, as no difference in the number of caspase-3+ SVZ cells was found between EAE mice and HC (data not shown).Table 1


Persistent inflammation alters the function of the endogenous brain stem cell compartment.

Pluchino S, Muzio L, Imitola J, Deleidi M, Alfaro-Cervello C, Salani G, Porcheri C, Brambilla E, Cavasinni F, Bergamaschi A, Garcia-Verdugo JM, Comi G, Khoury SJ, Martino G - Brain (2008)

Chronic autoimmune CNS inflammation impairs proliferation of SVZ-resident NPCs in vivo. (A) Decrease of M-phase confined phosphorylated histone H3 (pH3)+ cells is observed in the SVZ of EAE mice at both 20, 30 and 60 dpi. Data in the graph are represented as mean numbers of pH3-immunoreactive cells/section ± SEM and have been obtained from a total of n ≥ 5 mice per group. *P ≤ 0.05, when compared with HC. Two representative images of pH3+ cells in the SVZ of HC and EAE 30 dpi are shown. Scale bars 50 μm. (B–E) Coronal sections of the dorsolateral SVZ from HC mice (B and D) and mice with EAE at 30 dpi (C and E) showing fast-proliferating IddU+ cells (green in B and C), IddU+/Iba1+ (green and red in B and C, respectively) and CD45+/Ki67+ (green and red in D and E, respectively) cells in EAE vs. HC. Arrowheads indicate Iddu–/Iba1+ cells in both panels. Scale bars: 50 μm. (F) Decrease of long-term BrdU-retaining cells is observed in the SVZ of EAE mice at 30 dpi. Mice received BrdU for 6 days starting from either 13 or 30 dpi and were sacrificed 40 days after the last BrdU injection. Data are represented as mean numbers of BrdU+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group from n ≥ 2 independent experiments. *P ≤ 0.001, when compared with HC. Two representative confocal microscopy pictures showing long term-retaining BrdU+ (red) GFAP+ (green) cells from the SVZ of HC and EAE 30 dpi are shown. (G) Decrease of SVZ cells expressing the mRNA for PDGFrα is observed in the SVZ of EAE mice at 20 dpi. PdgfRα mRNA is expressed by putative type slow-dividing cells located within the SVZ, as well as by OPCs that are widely distributed within the adult brain parenchyma (arrowheads in the upper panel). Data are represented as mean numbers of PDGFrα+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group. Scale bars: 50 μm. Nuclei in (B–G) have been counterstained with DAPI. LV, lateral ventricle.
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Figure 1: Chronic autoimmune CNS inflammation impairs proliferation of SVZ-resident NPCs in vivo. (A) Decrease of M-phase confined phosphorylated histone H3 (pH3)+ cells is observed in the SVZ of EAE mice at both 20, 30 and 60 dpi. Data in the graph are represented as mean numbers of pH3-immunoreactive cells/section ± SEM and have been obtained from a total of n ≥ 5 mice per group. *P ≤ 0.05, when compared with HC. Two representative images of pH3+ cells in the SVZ of HC and EAE 30 dpi are shown. Scale bars 50 μm. (B–E) Coronal sections of the dorsolateral SVZ from HC mice (B and D) and mice with EAE at 30 dpi (C and E) showing fast-proliferating IddU+ cells (green in B and C), IddU+/Iba1+ (green and red in B and C, respectively) and CD45+/Ki67+ (green and red in D and E, respectively) cells in EAE vs. HC. Arrowheads indicate Iddu–/Iba1+ cells in both panels. Scale bars: 50 μm. (F) Decrease of long-term BrdU-retaining cells is observed in the SVZ of EAE mice at 30 dpi. Mice received BrdU for 6 days starting from either 13 or 30 dpi and were sacrificed 40 days after the last BrdU injection. Data are represented as mean numbers of BrdU+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group from n ≥ 2 independent experiments. *P ≤ 0.001, when compared with HC. Two representative confocal microscopy pictures showing long term-retaining BrdU+ (red) GFAP+ (green) cells from the SVZ of HC and EAE 30 dpi are shown. (G) Decrease of SVZ cells expressing the mRNA for PDGFrα is observed in the SVZ of EAE mice at 20 dpi. PdgfRα mRNA is expressed by putative type slow-dividing cells located within the SVZ, as well as by OPCs that are widely distributed within the adult brain parenchyma (arrowheads in the upper panel). Data are represented as mean numbers of PDGFrα+ cells/section ± SEM and have been obtained from a total of n ≥ 3 mice per group. Scale bars: 50 μm. Nuclei in (B–G) have been counterstained with DAPI. LV, lateral ventricle.
Mentions: To study the rapidly dividing transit-amplifying progenitor cells (type C cells) we used short-term IddU labelling protocols (see Supplementary data). We did not find any significant difference in the cell cycle length (Tc) in the SVZ of EAE versus HC mice (Table 1). On the other hand, the GF of EAE mice at 20 and 30 dpi was significantly lower compared with HC (both P ≤ 0.05), though a return toward baseline values was observed between 60 and 90 dpi (Table 1). Accordingly, a significant reduction in the absolute numbers of M-phase-confined phosphorylated histone H3 (pH3)+ SVZ cells was observed in EAE mice at 20, 30 and 60 dpi (Figure 1A) when compared with HC (all P ≤ 0.05). Again, a return toward baseline values in the numbers of pH3+ cells was observed in EAE at 90 dpi (data not shown). Finally, few—if any—IddU+/Iba1+ and/or CD45+/Ki67+ cells were found within the SVZ of EAE mice (Figure 1B–E), thus suggesting that the proliferation of either local microglial cells or CNS-infiltrating blood-derived leucocytes did not contribute significantly to the total GF quantified within the dorso-lateral SVZ. Apoptosis of neural cells could not account for the observed decreased GF, as no difference in the number of caspase-3+ SVZ cells was found between EAE mice and HC (data not shown).Table 1

Bottom Line: Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke), the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized.Here we show that persistent brain inflammation, induced by immune cells targeting myelin, extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche.Together, these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders.

View Article: PubMed Central - PubMed

Affiliation: Neuroimmunology Unit, DIBIT, San Raffaele Scientific Institute, Milano, Italy.

ABSTRACT
Endogenous neural stem/precursor cells (NPCs) are considered a functional reservoir for promoting tissue homeostasis and repair after injury, therefore regenerative strategies that mobilize these cells have recently been proposed. Despite evidence of increased neurogenesis upon acute inflammatory insults (e.g. ischaemic stroke), the plasticity of the endogenous brain stem cell compartment in chronic CNS inflammatory disorders remains poorly characterized. Here we show that persistent brain inflammation, induced by immune cells targeting myelin, extensively alters the proliferative and migratory properties of subventricular zone (SVZ)-resident NPCs in vivo leading to significant accumulation of non-migratory neuroblasts within the SVZ germinal niche. In parallel, we demonstrate a quantitative reduction of the putative brain stem cells proliferation in the SVZ during persistent brain inflammation, which is completely reversed after in vitro culture of the isolated NPCs. Together, these data indicate that the inflamed brain microenvironment sustains a non cell-autonomous dysfunction of the endogenous CNS stem cell compartment and challenge the potential efficacy of proposed therapies aimed at mobilizing endogenous precursors in chronic inflammatory brain disorders.

Show MeSH
Related in: MedlinePlus