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Molecular aging and rejuvenation of human muscle stem cells.

Carlson ME, Suetta C, Conboy MJ, Aagaard P, Mackey A, Kjaer M, Conboy I - EMBO Mol Med (2009)

Bottom Line: This molecular understanding, combined with data that human satellite cells remain intrinsically young, introduced novel therapeutic targets.Indeed, activation of MAPK/Notch restored 'youthful' myogenic responses to satellite cells from 70-year-old humans, rendering them similar to cells from 20-year-old humans.These findings strongly suggest that aging of human muscle maintenance and repair can be reversed by 'youthful' calibration of specific molecular pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of California, Berkeley, Berkeley CA, USA.

ABSTRACT
Very little remains known about the regulation of human organ stem cells (in general, and during the aging process), and most previous data were collected in short-lived rodents. We examined whether stem cell aging in rodents could be extrapolated to genetically and environmentally variable humans. Our findings establish key evolutionarily conserved mechanisms of human stem cell aging. We find that satellite cells are maintained in aged human skeletal muscle, but fail to activate in response to muscle attrition, due to diminished activation of Notch compounded by elevated transforming growth factor beta (TGF-beta)/phospho Smad3 (pSmad3). Furthermore, this work reveals that mitogen-activated protein kinase (MAPK)/phosphate extracellular signal-regulated kinase (pERK) signalling declines in human muscle with age, and is important for activating Notch in human muscle stem cells. This molecular understanding, combined with data that human satellite cells remain intrinsically young, introduced novel therapeutic targets. Indeed, activation of MAPK/Notch restored 'youthful' myogenic responses to satellite cells from 70-year-old humans, rendering them similar to cells from 20-year-old humans. These findings strongly suggest that aging of human muscle maintenance and repair can be reversed by 'youthful' calibration of specific molecular pathways.

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Mechanisms of muscle stem cell aging are conserved between mice and humans, with respect to TGF-β signalling imbalanceImmunodetection of:A. TGF-β (green) and laminin (red),B. P-Smad3 (green) and laminin (red) is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blotting for TGF-β, P-Smad3, p15, p21, p16 and p27 from whole muscle protein lysates; quantified in D. Actin was used as loading control. *P ≤ 0.05, old compared with young. Significant age-specific elevation of TGF-β/pSmad and of CDK inhibitors, p15 and p21 was detected in old muscle as compared to young.E, F. Activated satellite cells were cultured for 24 h in OPTI-MEM containing age-matched human sera in the presence of 25 ng/ml recombinant TGF-β1. Myogenic responses were analysed and quantified F, based on the co-expression of desmin/BrdU. Data are means ± s.d., n = 10–15 for immunodetection of cryosections, n = 6 for Western blotting analysis, n = 6 for myogenic culture experiments.
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fig04: Mechanisms of muscle stem cell aging are conserved between mice and humans, with respect to TGF-β signalling imbalanceImmunodetection of:A. TGF-β (green) and laminin (red),B. P-Smad3 (green) and laminin (red) is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blotting for TGF-β, P-Smad3, p15, p21, p16 and p27 from whole muscle protein lysates; quantified in D. Actin was used as loading control. *P ≤ 0.05, old compared with young. Significant age-specific elevation of TGF-β/pSmad and of CDK inhibitors, p15 and p21 was detected in old muscle as compared to young.E, F. Activated satellite cells were cultured for 24 h in OPTI-MEM containing age-matched human sera in the presence of 25 ng/ml recombinant TGF-β1. Myogenic responses were analysed and quantified F, based on the co-expression of desmin/BrdU. Data are means ± s.d., n = 10–15 for immunodetection of cryosections, n = 6 for Western blotting analysis, n = 6 for myogenic culture experiments.

Mentions: Remarkably, as shown in Fig 4, these molecular signatures of aging within the muscle stem cell compartment are conserved between mouse and human that suggests the fundamental significance of uncovered regulatory mechanisms. As compared to young, old human muscle fibres contain higher levels of TGF-β, which associates with the laminin-rich basement membrane of the satellite cell microniche (Fig 4A). Accordingly, levels of nuclear pSmad3 (the transcriptional factor that is activated by TGF-β signalling) are excessive in old human satellite cells, as compared to youngs (Fig 4B). To further confirm these results in a more quantitative way, we also performed Western blot analysis of young and old human muscles. As shown in Fig 4C (quantified in Fig 4D), the levels of TGF-β, pSmad3 and CDK inhibitors, p15 and p21 (known to be induced by TGF-β signalling and reduced by active Notch) are all higher in the old, as compared to young human muscle. Interestingly, p27 and p16 were undetectable in either young or old tissue, suggesting that these CDK inhibitors do not play a major role in studied processes. Efficient immuno-detection of p27 and p16 with the same antibodies was performed using positive control protein extracts (not shown).


Molecular aging and rejuvenation of human muscle stem cells.

Carlson ME, Suetta C, Conboy MJ, Aagaard P, Mackey A, Kjaer M, Conboy I - EMBO Mol Med (2009)

Mechanisms of muscle stem cell aging are conserved between mice and humans, with respect to TGF-β signalling imbalanceImmunodetection of:A. TGF-β (green) and laminin (red),B. P-Smad3 (green) and laminin (red) is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blotting for TGF-β, P-Smad3, p15, p21, p16 and p27 from whole muscle protein lysates; quantified in D. Actin was used as loading control. *P ≤ 0.05, old compared with young. Significant age-specific elevation of TGF-β/pSmad and of CDK inhibitors, p15 and p21 was detected in old muscle as compared to young.E, F. Activated satellite cells were cultured for 24 h in OPTI-MEM containing age-matched human sera in the presence of 25 ng/ml recombinant TGF-β1. Myogenic responses were analysed and quantified F, based on the co-expression of desmin/BrdU. Data are means ± s.d., n = 10–15 for immunodetection of cryosections, n = 6 for Western blotting analysis, n = 6 for myogenic culture experiments.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2875071&req=5

fig04: Mechanisms of muscle stem cell aging are conserved between mice and humans, with respect to TGF-β signalling imbalanceImmunodetection of:A. TGF-β (green) and laminin (red),B. P-Smad3 (green) and laminin (red) is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blotting for TGF-β, P-Smad3, p15, p21, p16 and p27 from whole muscle protein lysates; quantified in D. Actin was used as loading control. *P ≤ 0.05, old compared with young. Significant age-specific elevation of TGF-β/pSmad and of CDK inhibitors, p15 and p21 was detected in old muscle as compared to young.E, F. Activated satellite cells were cultured for 24 h in OPTI-MEM containing age-matched human sera in the presence of 25 ng/ml recombinant TGF-β1. Myogenic responses were analysed and quantified F, based on the co-expression of desmin/BrdU. Data are means ± s.d., n = 10–15 for immunodetection of cryosections, n = 6 for Western blotting analysis, n = 6 for myogenic culture experiments.
Mentions: Remarkably, as shown in Fig 4, these molecular signatures of aging within the muscle stem cell compartment are conserved between mouse and human that suggests the fundamental significance of uncovered regulatory mechanisms. As compared to young, old human muscle fibres contain higher levels of TGF-β, which associates with the laminin-rich basement membrane of the satellite cell microniche (Fig 4A). Accordingly, levels of nuclear pSmad3 (the transcriptional factor that is activated by TGF-β signalling) are excessive in old human satellite cells, as compared to youngs (Fig 4B). To further confirm these results in a more quantitative way, we also performed Western blot analysis of young and old human muscles. As shown in Fig 4C (quantified in Fig 4D), the levels of TGF-β, pSmad3 and CDK inhibitors, p15 and p21 (known to be induced by TGF-β signalling and reduced by active Notch) are all higher in the old, as compared to young human muscle. Interestingly, p27 and p16 were undetectable in either young or old tissue, suggesting that these CDK inhibitors do not play a major role in studied processes. Efficient immuno-detection of p27 and p16 with the same antibodies was performed using positive control protein extracts (not shown).

Bottom Line: This molecular understanding, combined with data that human satellite cells remain intrinsically young, introduced novel therapeutic targets.Indeed, activation of MAPK/Notch restored 'youthful' myogenic responses to satellite cells from 70-year-old humans, rendering them similar to cells from 20-year-old humans.These findings strongly suggest that aging of human muscle maintenance and repair can be reversed by 'youthful' calibration of specific molecular pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of California, Berkeley, Berkeley CA, USA.

ABSTRACT
Very little remains known about the regulation of human organ stem cells (in general, and during the aging process), and most previous data were collected in short-lived rodents. We examined whether stem cell aging in rodents could be extrapolated to genetically and environmentally variable humans. Our findings establish key evolutionarily conserved mechanisms of human stem cell aging. We find that satellite cells are maintained in aged human skeletal muscle, but fail to activate in response to muscle attrition, due to diminished activation of Notch compounded by elevated transforming growth factor beta (TGF-beta)/phospho Smad3 (pSmad3). Furthermore, this work reveals that mitogen-activated protein kinase (MAPK)/phosphate extracellular signal-regulated kinase (pERK) signalling declines in human muscle with age, and is important for activating Notch in human muscle stem cells. This molecular understanding, combined with data that human satellite cells remain intrinsically young, introduced novel therapeutic targets. Indeed, activation of MAPK/Notch restored 'youthful' myogenic responses to satellite cells from 70-year-old humans, rendering them similar to cells from 20-year-old humans. These findings strongly suggest that aging of human muscle maintenance and repair can be reversed by 'youthful' calibration of specific molecular pathways.

Show MeSH
Related in: MedlinePlus