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Endogenous IGF-1 regulates the neuronal differentiation of adult stem cells
G J Brooker1, M Kalloniatis, V C Russo
1The Walter and Eliza Hall Institute of Medical Research, The Royal Melbourne Hospital, Parkville, Victoria, Australia.
Abstract:
Stem cells from the adult forebrain of mice were stimulated to form clones in vitro using fibroblast growth factor-2 (FGF-2). At concentrations above 10 ng/ml of FGF-2, very few clones gave rise to neurons; however, if FGF-2 was removed after 5 days, 20-30% of clones subsequently gave rise to neurons. The number of neuron-containing clones and the number of neurons per clone was significantly enhanced, if insulin-like growth factor (IGF)-1 or heparin were added subsequent to FGF-2 removal. The spontaneous production of neurons after FGF-2 removal was shown to be due to endogenous IGF-1, since antibodies to IGF-1 and an IGF-1 binding protein totally inhibited neuronal production. Similarly, these reagents also abrogated the neuron-promoting effects of heparin. Thus, it appears that endogenous IGF-1 may be a major regulator of stem cell differentiation into neurons. Furthermore, it was found that high levels of IGF-1 or insulin promoted the maturation and affected the neurotransmitter phenotype of the neurons generated.
Insights
Removing fibroblast growth factor-2 (FGF-2) allowed mouse stem cells to generate neurons. Adding insulin-like growth factor (IGF)-1 or heparin further boosted neuron production, highlighting IGF-1
Area of Science:
- Neuroscience
- Developmental Biology
- Stem Cell Research
Background:
- Adult mouse forebrain stem cells can proliferate in vitro.
- Fibroblast growth factor-2 (FGF-2) is a key mitogen for these stem cells.
Purpose of the Study:
- To investigate the role of FGF-2 withdrawal and subsequent factors in neuronal differentiation.
- To identify endogenous regulators of stem cell neurogenesis.
Main Methods:
- Culturing adult mouse forebrain stem cells with varying FGF-2 concentrations.
- Assessing neuronal differentiation after FGF-2 removal.
- Supplementing cultures with insulin-like growth factor (IGF)-1 or heparin.
- Utilizing antibodies against IGF-1 to block its activity.
Main Results:
- High FGF-2 concentrations inhibited neuronal differentiation.
- FGF-2 removal after 5 days induced neuronal differentiation in 20-30% of clones.
- IGF-1 or heparin addition post-FGF-2 removal significantly increased neuron production.
- Endogenous IGF-1 was identified as a critical mediator of spontaneous neurogenesis.
- Heparin's pro-neuronal effect was dependent on endogenous IGF-1.
Conclusions:
- Endogenous IGF-1 is a major regulator of adult forebrain stem cell differentiation into neurons.
- The timing of FGF-2 withdrawal is crucial for initiating neurogenesis.
- IGF-1 and insulin influence neuronal maturation and neurotransmitter phenotype.