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Interleukin-15 regulates proliferation and self-renewal of adult neural stem cells.

Gómez-Nicola D, Valle-Argos B, Pallas-Bazarra N, Nieto-Sampedro M - Mol. Biol. Cell (2011)

Bottom Line: Moreover, IL-15-deficient NSCs were more prone to differentiate than wild-type NSCs, not affecting the cell population balance.Lack of IL-15 led to a defective activation of the JAK/STAT and ERK pathways, key for the regulation of proliferation and differentiation of NSCs.The results show that IL-15 is a key regulator of neurogenesis in the adult and is essential to understanding diseases with an inflammatory component.

View Article: PubMed Central - PubMed

Affiliation: Functional and Systems Neurobiology Department, Cajal Institute (CSIC), Madrid, Spain. dgomeznicola@gmail.com

ABSTRACT
The impact of inflammation is crucial for the regulation of the biology of neural stem cells (NSCs). Interleukin-15 (IL-15) appears as a likely candidate for regulating neurogenesis, based on its well-known mitogenic properties. We show here that NSCs of the subventricular zone (SVZ) express IL-15, which regulates NSC proliferation, as evidenced by the study of IL-15-/- mice and the effects of acute IL-15 administration, coupled to 5-bromo-2'-deoxyuridine/5-ethynyl-2'-deoxyuridine dual-pulse labeling. Moreover, IL-15 regulates NSC differentiation, its deficiency leading to an impaired generation of neuroblasts in the SVZ-rostral migratory stream axis, recoverable through the action of exogenous IL-15. IL-15 expressed in cultured NSCs is linked to self-renewal, proliferation, and differentiation. IL-15-/- NSCs presented deficient proliferation and self-renewal, as evidenced in proliferation and colony-forming assays and the analysis of cell cycle-regulatory proteins. Moreover, IL-15-deficient NSCs were more prone to differentiate than wild-type NSCs, not affecting the cell population balance. Lack of IL-15 led to a defective activation of the JAK/STAT and ERK pathways, key for the regulation of proliferation and differentiation of NSCs. The results show that IL-15 is a key regulator of neurogenesis in the adult and is essential to understanding diseases with an inflammatory component.

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IL-15 is expressed in neurospheres during proliferation and differentiation. (A–F) Immunocytochemical analysis of the expression of IL-15 (red; A, C, D, F) in nestin-positive (green; B, C) or DCX-positive (green; E, F) cells. Magnifications are shown in the right-hand inset, indicating colocalization with white arrowheads. Nuclei are stained with Hoechst (blue). Neurospheres were evaluated with confocal microscopy. Scale bar in A–F, 20 μm (shown in F). (G) RT-PCR analysis of IL-15 mRNA expression under proliferative culture conditions (+EGF, +FGF) at 24, 48, and 72 h. Resting neurospheres (without EGF or FGF) were used as control (CTL). GAPDH expression was used as housekeeping gene. (H) RT-PCR analysis of IL-15 mRNA expression under differentiation culture conditions (+2% FBS) at 4, 7, and 10 d. Proliferative neurospheres (+EGF, +FGF) were used as control. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression was used as housekeeping gene.
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Figure 5: IL-15 is expressed in neurospheres during proliferation and differentiation. (A–F) Immunocytochemical analysis of the expression of IL-15 (red; A, C, D, F) in nestin-positive (green; B, C) or DCX-positive (green; E, F) cells. Magnifications are shown in the right-hand inset, indicating colocalization with white arrowheads. Nuclei are stained with Hoechst (blue). Neurospheres were evaluated with confocal microscopy. Scale bar in A–F, 20 μm (shown in F). (G) RT-PCR analysis of IL-15 mRNA expression under proliferative culture conditions (+EGF, +FGF) at 24, 48, and 72 h. Resting neurospheres (without EGF or FGF) were used as control (CTL). GAPDH expression was used as housekeeping gene. (H) RT-PCR analysis of IL-15 mRNA expression under differentiation culture conditions (+2% FBS) at 4, 7, and 10 d. Proliferative neurospheres (+EGF, +FGF) were used as control. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression was used as housekeeping gene.

Mentions: The results obtained in vivo led us to analyze the effect of IL-15 on the biology of cultured neural stem cells (neurospheres). First, we observed that IL-15 was expressed in neurospheres, being expressed by a small number of cells within the neurosphere mass (Figure 5, A and D). The IL-15-expressing cells were a subgroup of nestin-positive (Figure 5B) and DCX-positive (Figure 5E) cells, as shown by immunocytochemical colocalization (Figure 5, C and F). The expression of IL-15 mRNA was found under nonproliferating conditions (Figure 5G; CTL) but was upregulated upon proliferative stimulation with epidermal growth factor (EGF) and fibroblast growth factor (FGF), reaching its maximal expression at 24 h after the stimuli, to further decrease (Figure 5G). On the other hand, the elevated expression of IL-15 during proliferation (EGF + FGF) decreases when neurospheres are cultured under adherent and differentiation conditions (2% fetal bovine serum [FBS]), as observed after a 4- to 10-d differentiation paradigm (Figure 5H).


Interleukin-15 regulates proliferation and self-renewal of adult neural stem cells.

Gómez-Nicola D, Valle-Argos B, Pallas-Bazarra N, Nieto-Sampedro M - Mol. Biol. Cell (2011)

IL-15 is expressed in neurospheres during proliferation and differentiation. (A–F) Immunocytochemical analysis of the expression of IL-15 (red; A, C, D, F) in nestin-positive (green; B, C) or DCX-positive (green; E, F) cells. Magnifications are shown in the right-hand inset, indicating colocalization with white arrowheads. Nuclei are stained with Hoechst (blue). Neurospheres were evaluated with confocal microscopy. Scale bar in A–F, 20 μm (shown in F). (G) RT-PCR analysis of IL-15 mRNA expression under proliferative culture conditions (+EGF, +FGF) at 24, 48, and 72 h. Resting neurospheres (without EGF or FGF) were used as control (CTL). GAPDH expression was used as housekeeping gene. (H) RT-PCR analysis of IL-15 mRNA expression under differentiation culture conditions (+2% FBS) at 4, 7, and 10 d. Proliferative neurospheres (+EGF, +FGF) were used as control. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression was used as housekeeping gene.
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Related In: Results  -  Collection

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Figure 5: IL-15 is expressed in neurospheres during proliferation and differentiation. (A–F) Immunocytochemical analysis of the expression of IL-15 (red; A, C, D, F) in nestin-positive (green; B, C) or DCX-positive (green; E, F) cells. Magnifications are shown in the right-hand inset, indicating colocalization with white arrowheads. Nuclei are stained with Hoechst (blue). Neurospheres were evaluated with confocal microscopy. Scale bar in A–F, 20 μm (shown in F). (G) RT-PCR analysis of IL-15 mRNA expression under proliferative culture conditions (+EGF, +FGF) at 24, 48, and 72 h. Resting neurospheres (without EGF or FGF) were used as control (CTL). GAPDH expression was used as housekeeping gene. (H) RT-PCR analysis of IL-15 mRNA expression under differentiation culture conditions (+2% FBS) at 4, 7, and 10 d. Proliferative neurospheres (+EGF, +FGF) were used as control. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression was used as housekeeping gene.
Mentions: The results obtained in vivo led us to analyze the effect of IL-15 on the biology of cultured neural stem cells (neurospheres). First, we observed that IL-15 was expressed in neurospheres, being expressed by a small number of cells within the neurosphere mass (Figure 5, A and D). The IL-15-expressing cells were a subgroup of nestin-positive (Figure 5B) and DCX-positive (Figure 5E) cells, as shown by immunocytochemical colocalization (Figure 5, C and F). The expression of IL-15 mRNA was found under nonproliferating conditions (Figure 5G; CTL) but was upregulated upon proliferative stimulation with epidermal growth factor (EGF) and fibroblast growth factor (FGF), reaching its maximal expression at 24 h after the stimuli, to further decrease (Figure 5G). On the other hand, the elevated expression of IL-15 during proliferation (EGF + FGF) decreases when neurospheres are cultured under adherent and differentiation conditions (2% fetal bovine serum [FBS]), as observed after a 4- to 10-d differentiation paradigm (Figure 5H).

Bottom Line: Moreover, IL-15-deficient NSCs were more prone to differentiate than wild-type NSCs, not affecting the cell population balance.Lack of IL-15 led to a defective activation of the JAK/STAT and ERK pathways, key for the regulation of proliferation and differentiation of NSCs.The results show that IL-15 is a key regulator of neurogenesis in the adult and is essential to understanding diseases with an inflammatory component.

View Article: PubMed Central - PubMed

Affiliation: Functional and Systems Neurobiology Department, Cajal Institute (CSIC), Madrid, Spain. dgomeznicola@gmail.com

ABSTRACT
The impact of inflammation is crucial for the regulation of the biology of neural stem cells (NSCs). Interleukin-15 (IL-15) appears as a likely candidate for regulating neurogenesis, based on its well-known mitogenic properties. We show here that NSCs of the subventricular zone (SVZ) express IL-15, which regulates NSC proliferation, as evidenced by the study of IL-15-/- mice and the effects of acute IL-15 administration, coupled to 5-bromo-2'-deoxyuridine/5-ethynyl-2'-deoxyuridine dual-pulse labeling. Moreover, IL-15 regulates NSC differentiation, its deficiency leading to an impaired generation of neuroblasts in the SVZ-rostral migratory stream axis, recoverable through the action of exogenous IL-15. IL-15 expressed in cultured NSCs is linked to self-renewal, proliferation, and differentiation. IL-15-/- NSCs presented deficient proliferation and self-renewal, as evidenced in proliferation and colony-forming assays and the analysis of cell cycle-regulatory proteins. Moreover, IL-15-deficient NSCs were more prone to differentiate than wild-type NSCs, not affecting the cell population balance. Lack of IL-15 led to a defective activation of the JAK/STAT and ERK pathways, key for the regulation of proliferation and differentiation of NSCs. The results show that IL-15 is a key regulator of neurogenesis in the adult and is essential to understanding diseases with an inflammatory component.

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