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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 regulates proliferation and self-renewal of NSCs. (A) Effect of IL-15 on the proliferation of neurospheres, evaluated by the MTT assay. Cells were cultured in incomplete medium (CTL) or incomplete medium supplemented with IL-15 (5 ng/ml) for 24, 48, or 72 h. Data are expressed as mean ± SEM of optical density (OD) 595 nm. (B) Effect of IL-15 deficiency on the proliferation of neurospheres, evaluated by the MTT assay. WT or IL-15 knockout cells were cultured in complete medium for 24, 48, or 72 h. Data are expressed as mean ± SEM of OD 595 nm. (C) Western blotting analysis of the expression of the cell cycle regulators cyclin D1, cyclin D3, CDK4, CDK6, phospho Rb (pRb), phospho histone H3 (pHH3), p21, p27, and p15, using GAPDH as housekeeping gene. WT or IL-15 knockout (KO) neurospheres were cultured for 12, 24, or 48 h in complete medium to further analyze protein expression. (D) Phase contrast analysis of neurosphere size after a self-renewal assay. WT (black bars) and IL-15 knockout (white bars) cells were cultured in complete medium for 7 d to quantify the number of individual cells able to generate a neurosphere (E) and the size of the generated neurospheres (F). (E) Data are expressed as mean ± SEM of the number of neurospheres/well when 5, 50 or 500 cells/well were initially plated. (F) Data are expressed as mean ± SEM of the neurosphere diameter (μm). Scale bar in D, 50 μm. Statistical differences of CTL vs. IL-15 (A), WT vs. IL15 knockout (B, E, F): *p < 0.05, **p < 0.01, ***p < 0.001. Data were analyzed with an ANOVA and a post hoc Tukey test.
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Figure 6: IL-15 regulates proliferation and self-renewal of NSCs. (A) Effect of IL-15 on the proliferation of neurospheres, evaluated by the MTT assay. Cells were cultured in incomplete medium (CTL) or incomplete medium supplemented with IL-15 (5 ng/ml) for 24, 48, or 72 h. Data are expressed as mean ± SEM of optical density (OD) 595 nm. (B) Effect of IL-15 deficiency on the proliferation of neurospheres, evaluated by the MTT assay. WT or IL-15 knockout cells were cultured in complete medium for 24, 48, or 72 h. Data are expressed as mean ± SEM of OD 595 nm. (C) Western blotting analysis of the expression of the cell cycle regulators cyclin D1, cyclin D3, CDK4, CDK6, phospho Rb (pRb), phospho histone H3 (pHH3), p21, p27, and p15, using GAPDH as housekeeping gene. WT or IL-15 knockout (KO) neurospheres were cultured for 12, 24, or 48 h in complete medium to further analyze protein expression. (D) Phase contrast analysis of neurosphere size after a self-renewal assay. WT (black bars) and IL-15 knockout (white bars) cells were cultured in complete medium for 7 d to quantify the number of individual cells able to generate a neurosphere (E) and the size of the generated neurospheres (F). (E) Data are expressed as mean ± SEM of the number of neurospheres/well when 5, 50 or 500 cells/well were initially plated. (F) Data are expressed as mean ± SEM of the neurosphere diameter (μm). Scale bar in D, 50 μm. Statistical differences of CTL vs. IL-15 (A), WT vs. IL15 knockout (B, E, F): *p < 0.05, **p < 0.01, ***p < 0.001. Data were analyzed with an ANOVA and a post hoc Tukey test.

Mentions: The previously obtained results with different in vivo or in vitro experimental paradigms led us to question whether IL-15 is important for NSC proliferation and/or self-renewal. Therefore, using cultured neurospheres derived from WT or IL-15−/− mice, we analyzed the effect of exogenous IL-15 on neurosphere proliferation and self-renewal. First, WT neurospheres significantly increase their proliferation when stimulated with recombinant exogenous IL-15 under nonproliferative culture conditions (Nb + B27 supplement; Figure 6A). Second, when WT or IL-15−/− neurospheres were cultured under proliferative conditions (Nb + B27 + EGF + FGF), we observed a deficiency of IL-15−/−-derived neurospheres to reach a normal WT proliferative rate (Figure 6B). IL-15−/−-derived neurospheres showed a significant reduction in their proliferation at both 48 and 72 h after the addition of the mitogenic boost (Figure 6B).


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 regulates proliferation and self-renewal of NSCs. (A) Effect of IL-15 on the proliferation of neurospheres, evaluated by the MTT assay. Cells were cultured in incomplete medium (CTL) or incomplete medium supplemented with IL-15 (5 ng/ml) for 24, 48, or 72 h. Data are expressed as mean ± SEM of optical density (OD) 595 nm. (B) Effect of IL-15 deficiency on the proliferation of neurospheres, evaluated by the MTT assay. WT or IL-15 knockout cells were cultured in complete medium for 24, 48, or 72 h. Data are expressed as mean ± SEM of OD 595 nm. (C) Western blotting analysis of the expression of the cell cycle regulators cyclin D1, cyclin D3, CDK4, CDK6, phospho Rb (pRb), phospho histone H3 (pHH3), p21, p27, and p15, using GAPDH as housekeeping gene. WT or IL-15 knockout (KO) neurospheres were cultured for 12, 24, or 48 h in complete medium to further analyze protein expression. (D) Phase contrast analysis of neurosphere size after a self-renewal assay. WT (black bars) and IL-15 knockout (white bars) cells were cultured in complete medium for 7 d to quantify the number of individual cells able to generate a neurosphere (E) and the size of the generated neurospheres (F). (E) Data are expressed as mean ± SEM of the number of neurospheres/well when 5, 50 or 500 cells/well were initially plated. (F) Data are expressed as mean ± SEM of the neurosphere diameter (μm). Scale bar in D, 50 μm. Statistical differences of CTL vs. IL-15 (A), WT vs. IL15 knockout (B, E, F): *p < 0.05, **p < 0.01, ***p < 0.001. Data were analyzed with an ANOVA and a post hoc Tukey test.
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Figure 6: IL-15 regulates proliferation and self-renewal of NSCs. (A) Effect of IL-15 on the proliferation of neurospheres, evaluated by the MTT assay. Cells were cultured in incomplete medium (CTL) or incomplete medium supplemented with IL-15 (5 ng/ml) for 24, 48, or 72 h. Data are expressed as mean ± SEM of optical density (OD) 595 nm. (B) Effect of IL-15 deficiency on the proliferation of neurospheres, evaluated by the MTT assay. WT or IL-15 knockout cells were cultured in complete medium for 24, 48, or 72 h. Data are expressed as mean ± SEM of OD 595 nm. (C) Western blotting analysis of the expression of the cell cycle regulators cyclin D1, cyclin D3, CDK4, CDK6, phospho Rb (pRb), phospho histone H3 (pHH3), p21, p27, and p15, using GAPDH as housekeeping gene. WT or IL-15 knockout (KO) neurospheres were cultured for 12, 24, or 48 h in complete medium to further analyze protein expression. (D) Phase contrast analysis of neurosphere size after a self-renewal assay. WT (black bars) and IL-15 knockout (white bars) cells were cultured in complete medium for 7 d to quantify the number of individual cells able to generate a neurosphere (E) and the size of the generated neurospheres (F). (E) Data are expressed as mean ± SEM of the number of neurospheres/well when 5, 50 or 500 cells/well were initially plated. (F) Data are expressed as mean ± SEM of the neurosphere diameter (μm). Scale bar in D, 50 μm. Statistical differences of CTL vs. IL-15 (A), WT vs. IL15 knockout (B, E, F): *p < 0.05, **p < 0.01, ***p < 0.001. Data were analyzed with an ANOVA and a post hoc Tukey test.
Mentions: The previously obtained results with different in vivo or in vitro experimental paradigms led us to question whether IL-15 is important for NSC proliferation and/or self-renewal. Therefore, using cultured neurospheres derived from WT or IL-15−/− mice, we analyzed the effect of exogenous IL-15 on neurosphere proliferation and self-renewal. First, WT neurospheres significantly increase their proliferation when stimulated with recombinant exogenous IL-15 under nonproliferative culture conditions (Nb + B27 supplement; Figure 6A). Second, when WT or IL-15−/− neurospheres were cultured under proliferative conditions (Nb + B27 + EGF + FGF), we observed a deficiency of IL-15−/−-derived neurospheres to reach a normal WT proliferative rate (Figure 6B). IL-15−/−-derived neurospheres showed a significant reduction in their proliferation at both 48 and 72 h after the addition of the mitogenic boost (Figure 6B).

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.

Show MeSH
Related in: MedlinePlus