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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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Notch activation and Delta upregulation is diminished in regenerating old human skeletal muscleA. Cryosections were analysed by immunostaining for co-expression of nuclear Pax7+/active Notch in resident satellite cells.B. Delta (red) and dystrophin (green) immuno-detection is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blot of Notch and Delta levels on whole muscle protein isolates for 2 week + 3 day; quantified in D. *P ≤ 0.05, old compared with young for both Notch and Delta.E. Quantification of Notch/Pax7 double-positive myofibre-associated cells from cryosections. Data are means ± s.d., n = 10–15 for immunodetection of cryosections. n = 6 for Western blotting analysis. As compared to young tissue, in old muscle loaded after immobility, there is significant down-regulation of Delta, active Notch and decline in numbers of myofibre-associated myogenic cells that co-express Pax7 and active Notch.
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fig03: Notch activation and Delta upregulation is diminished in regenerating old human skeletal muscleA. Cryosections were analysed by immunostaining for co-expression of nuclear Pax7+/active Notch in resident satellite cells.B. Delta (red) and dystrophin (green) immuno-detection is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blot of Notch and Delta levels on whole muscle protein isolates for 2 week + 3 day; quantified in D. *P ≤ 0.05, old compared with young for both Notch and Delta.E. Quantification of Notch/Pax7 double-positive myofibre-associated cells from cryosections. Data are means ± s.d., n = 10–15 for immunodetection of cryosections. n = 6 for Western blotting analysis. As compared to young tissue, in old muscle loaded after immobility, there is significant down-regulation of Delta, active Notch and decline in numbers of myofibre-associated myogenic cells that co-express Pax7 and active Notch.

Mentions: To establish whether Notch activation is lacking in old human satellite cells associated with aged muscle in vivo, we performed Notch and Pax7 co-immunodetection experiments in cryosections of human muscle biopsies. As shown in Fig 3A (and Fig S3 of Supporting Information), nuclear active Notch is eagerly detected in Pax7+ myofibre-associated cells. Furthermore, we also found that levels of the Notch ligand Delta are diminished in old myofibres, as compared to young myofibres (Fig 3B). In agreement with these data, decline in active Notch and its ligand Delta is observed in Western blot analysis of young and old human muscle (Fig 3C, D).


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)

Notch activation and Delta upregulation is diminished in regenerating old human skeletal muscleA. Cryosections were analysed by immunostaining for co-expression of nuclear Pax7+/active Notch in resident satellite cells.B. Delta (red) and dystrophin (green) immuno-detection is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blot of Notch and Delta levels on whole muscle protein isolates for 2 week + 3 day; quantified in D. *P ≤ 0.05, old compared with young for both Notch and Delta.E. Quantification of Notch/Pax7 double-positive myofibre-associated cells from cryosections. Data are means ± s.d., n = 10–15 for immunodetection of cryosections. n = 6 for Western blotting analysis. As compared to young tissue, in old muscle loaded after immobility, there is significant down-regulation of Delta, active Notch and decline in numbers of myofibre-associated myogenic cells that co-express Pax7 and active Notch.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2875071&req=5

fig03: Notch activation and Delta upregulation is diminished in regenerating old human skeletal muscleA. Cryosections were analysed by immunostaining for co-expression of nuclear Pax7+/active Notch in resident satellite cells.B. Delta (red) and dystrophin (green) immuno-detection is shown for 10 µm skeletal muscle cryosections. Hoechst labels nuclei (blue).C, D. Western blot of Notch and Delta levels on whole muscle protein isolates for 2 week + 3 day; quantified in D. *P ≤ 0.05, old compared with young for both Notch and Delta.E. Quantification of Notch/Pax7 double-positive myofibre-associated cells from cryosections. Data are means ± s.d., n = 10–15 for immunodetection of cryosections. n = 6 for Western blotting analysis. As compared to young tissue, in old muscle loaded after immobility, there is significant down-regulation of Delta, active Notch and decline in numbers of myofibre-associated myogenic cells that co-express Pax7 and active Notch.
Mentions: To establish whether Notch activation is lacking in old human satellite cells associated with aged muscle in vivo, we performed Notch and Pax7 co-immunodetection experiments in cryosections of human muscle biopsies. As shown in Fig 3A (and Fig S3 of Supporting Information), nuclear active Notch is eagerly detected in Pax7+ myofibre-associated cells. Furthermore, we also found that levels of the Notch ligand Delta are diminished in old myofibres, as compared to young myofibres (Fig 3B). In agreement with these data, decline in active Notch and its ligand Delta is observed in Western blot analysis of young and old human muscle (Fig 3C, D).

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