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IGF-I instructs multipotent adult neural progenitor cells to become oligodendrocytes.

Hsieh J, Aimone JB, Kaspar BK, Kuwabara T, Nakashima K, Gage FH - J. Cell Biol. (2004)

Bottom Line: Oligodendrocyte differentiation by IGF-I appears to be mediated through an inhibition of bone morphogenetic protein signaling.Furthermore, overexpression of IGF-I in the hippocampus leads to an increase in oligodendrocyte markers.These data demonstrate the existence of a single molecule, IGF-I, that can influence the fate choice of multipotent adult neural progenitor cells to an oligodendroglial lineage.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genetics, The Salk Institute, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA.

ABSTRACT
Adult multipotent neural progenitor cells can differentiate into neurons, astrocytes, and oligodendrocytes in the mammalian central nervous system, but the molecular mechanisms that control their differentiation are not yet well understood. Insulin-like growth factor I (IGF-I) can promote the differentiation of cells already committed to an oligodendroglial lineage during development. However, it is unclear whether IGF-I affects multipotent neural progenitor cells. Here, we show that IGF-I stimulates the differentiation of multipotent adult rat hippocampus-derived neural progenitor cells into oligodendrocytes. Modeling analysis indicates that the actions of IGF-I are instructive. Oligodendrocyte differentiation by IGF-I appears to be mediated through an inhibition of bone morphogenetic protein signaling. Furthermore, overexpression of IGF-I in the hippocampus leads to an increase in oligodendrocyte markers. These data demonstrate the existence of a single molecule, IGF-I, that can influence the fate choice of multipotent adult neural progenitor cells to an oligodendroglial lineage.

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Effect of IGF-I on the survival, proliferation, and instructive oligodendrocyte differentiation of adult neural progenitor cells. (A) Quantification of cell death in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures, as determined every 12 h by live staining with 1 μg/ml propidium iodide and 1 μg/ml Hoechst 33342. (B) Proliferation in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures as determined by BrdU incorporation. Parallel cultures were incubated with 2.5 μM BrdU at the beginning of each 12-h time point, immediately followed by fixation and BrdU staining. BrdU+ cells were counted as either being RIP− (blue and black columns) or RIP+ (red columns). All data are from at least three independent experiments in parallel cultures with error bars representing SDs.
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fig3: Effect of IGF-I on the survival, proliferation, and instructive oligodendrocyte differentiation of adult neural progenitor cells. (A) Quantification of cell death in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures, as determined every 12 h by live staining with 1 μg/ml propidium iodide and 1 μg/ml Hoechst 33342. (B) Proliferation in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures as determined by BrdU incorporation. Parallel cultures were incubated with 2.5 μM BrdU at the beginning of each 12-h time point, immediately followed by fixation and BrdU staining. BrdU+ cells were counted as either being RIP− (blue and black columns) or RIP+ (red columns). All data are from at least three independent experiments in parallel cultures with error bars representing SDs.

Mentions: Although these results establish IGF-I as an inducer of oligodendrocyte differentiation for a population of multipotent neural progenitor cells, it is more complicated to quantitatively assess the instructive versus selective effects of IGF-I. Therefore, we determined whether the increase of oligodendrocytes after IGF-I treatment could be due to a combination of selective oligodendrocyte survival, increased proliferation of progenitors, and/or instructive differentiation of progenitor cells to an oligodendroglial lineage. First, we directly measured the effect of IGF-I on cell survival. We asked whether a selective decrease in the death of oligodendrocytes (and/or oligodendrocyte progenitors) could explain the net increase in number of oligodendrocytes (defined by the expression of RIP, a marker of both immature and mature oligodendrocytes). If IGF-I had a selective survival effect on oligodendrocytes and/or their progenitors, we would expect to see a change in cell death due to the increased death of other cell types. To quantify cell death of the progeny of neural progenitor cells, living cultures were stained with 1 μg/ml propidium iodide, which stains dead cells, and 1 μg/ml Hoechst 33342, which stains live and dead cells. Staining of live (rather than fixed) cultures was used to avoid underestimating cell death due to possible detachment of dying and/or dead cells from culture substrates. This assay revealed a relatively small percentage of dead/dying cells, and one-way ANOVA analysis revealed no significant change (P = 0.3930) in the percentage of cells that died at any of the time points (Fig. 3 A). The amount of cell death in IGF-I–treated cultures was similar to the amount of cell death under standard proliferating conditions with FGF-2 (unpublished data). Cultures grown in the absence of IGF-I exhibited a progressive increase in overall cell death, reinforcing the role of IGF-I as an important factor for cell survival. Because there was minimal death and no significant difference in the percentage of dead/dying cells at each of the time points in the IGF-I–treated cultures, a selective survival of oligodendrocyte progenitors or oligodendrocytes does not appear to have a significant role in the increased net oligodendrocyte differentiation with IGF-I treatment.


IGF-I instructs multipotent adult neural progenitor cells to become oligodendrocytes.

Hsieh J, Aimone JB, Kaspar BK, Kuwabara T, Nakashima K, Gage FH - J. Cell Biol. (2004)

Effect of IGF-I on the survival, proliferation, and instructive oligodendrocyte differentiation of adult neural progenitor cells. (A) Quantification of cell death in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures, as determined every 12 h by live staining with 1 μg/ml propidium iodide and 1 μg/ml Hoechst 33342. (B) Proliferation in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures as determined by BrdU incorporation. Parallel cultures were incubated with 2.5 μM BrdU at the beginning of each 12-h time point, immediately followed by fixation and BrdU staining. BrdU+ cells were counted as either being RIP− (blue and black columns) or RIP+ (red columns). All data are from at least three independent experiments in parallel cultures with error bars representing SDs.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171962&req=5

fig3: Effect of IGF-I on the survival, proliferation, and instructive oligodendrocyte differentiation of adult neural progenitor cells. (A) Quantification of cell death in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures, as determined every 12 h by live staining with 1 μg/ml propidium iodide and 1 μg/ml Hoechst 33342. (B) Proliferation in insulin-free (no IGF-I) and IGF-I–treated (500 ng/ml) cultures as determined by BrdU incorporation. Parallel cultures were incubated with 2.5 μM BrdU at the beginning of each 12-h time point, immediately followed by fixation and BrdU staining. BrdU+ cells were counted as either being RIP− (blue and black columns) or RIP+ (red columns). All data are from at least three independent experiments in parallel cultures with error bars representing SDs.
Mentions: Although these results establish IGF-I as an inducer of oligodendrocyte differentiation for a population of multipotent neural progenitor cells, it is more complicated to quantitatively assess the instructive versus selective effects of IGF-I. Therefore, we determined whether the increase of oligodendrocytes after IGF-I treatment could be due to a combination of selective oligodendrocyte survival, increased proliferation of progenitors, and/or instructive differentiation of progenitor cells to an oligodendroglial lineage. First, we directly measured the effect of IGF-I on cell survival. We asked whether a selective decrease in the death of oligodendrocytes (and/or oligodendrocyte progenitors) could explain the net increase in number of oligodendrocytes (defined by the expression of RIP, a marker of both immature and mature oligodendrocytes). If IGF-I had a selective survival effect on oligodendrocytes and/or their progenitors, we would expect to see a change in cell death due to the increased death of other cell types. To quantify cell death of the progeny of neural progenitor cells, living cultures were stained with 1 μg/ml propidium iodide, which stains dead cells, and 1 μg/ml Hoechst 33342, which stains live and dead cells. Staining of live (rather than fixed) cultures was used to avoid underestimating cell death due to possible detachment of dying and/or dead cells from culture substrates. This assay revealed a relatively small percentage of dead/dying cells, and one-way ANOVA analysis revealed no significant change (P = 0.3930) in the percentage of cells that died at any of the time points (Fig. 3 A). The amount of cell death in IGF-I–treated cultures was similar to the amount of cell death under standard proliferating conditions with FGF-2 (unpublished data). Cultures grown in the absence of IGF-I exhibited a progressive increase in overall cell death, reinforcing the role of IGF-I as an important factor for cell survival. Because there was minimal death and no significant difference in the percentage of dead/dying cells at each of the time points in the IGF-I–treated cultures, a selective survival of oligodendrocyte progenitors or oligodendrocytes does not appear to have a significant role in the increased net oligodendrocyte differentiation with IGF-I treatment.

Bottom Line: Oligodendrocyte differentiation by IGF-I appears to be mediated through an inhibition of bone morphogenetic protein signaling.Furthermore, overexpression of IGF-I in the hippocampus leads to an increase in oligodendrocyte markers.These data demonstrate the existence of a single molecule, IGF-I, that can influence the fate choice of multipotent adult neural progenitor cells to an oligodendroglial lineage.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Genetics, The Salk Institute, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA.

ABSTRACT
Adult multipotent neural progenitor cells can differentiate into neurons, astrocytes, and oligodendrocytes in the mammalian central nervous system, but the molecular mechanisms that control their differentiation are not yet well understood. Insulin-like growth factor I (IGF-I) can promote the differentiation of cells already committed to an oligodendroglial lineage during development. However, it is unclear whether IGF-I affects multipotent neural progenitor cells. Here, we show that IGF-I stimulates the differentiation of multipotent adult rat hippocampus-derived neural progenitor cells into oligodendrocytes. Modeling analysis indicates that the actions of IGF-I are instructive. Oligodendrocyte differentiation by IGF-I appears to be mediated through an inhibition of bone morphogenetic protein signaling. Furthermore, overexpression of IGF-I in the hippocampus leads to an increase in oligodendrocyte markers. These data demonstrate the existence of a single molecule, IGF-I, that can influence the fate choice of multipotent adult neural progenitor cells to an oligodendroglial lineage.

Show MeSH