Supplement 12-1 What is the Relationship Between Replicative Cell Senescence & Functional Tissue...
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Transcript of Supplement 12-1 What is the Relationship Between Replicative Cell Senescence & Functional Tissue...
Supplement 12-1
What is the Relationship Between Replicative Cell Senescence & Functional Tissue Senescence.
Addition to Biology of Aging 3e by Robert Arking
Relationship between stress & telomeres?
von Ziglincki
psychological stress alters telomere length
Relationship between telomere length/replicative senescence, cell function & tissue senescence?
heart
skin
other tissues
Psychological Stress Induces Oxidative Stress & Shortens Telomeres
Epel et al., PNAS 101: 17312, 2005
Perceived Stress Makes You Age!
This, when combined with data from glucocorticoid studies, provides the mechanistic basis for the findings of the MIDUS twin study
Senescence of the Heart is Related to Changes in Cell
Demographics Brought About By Changes in Stem Cell Activity
Lakatta, Circulation 107:490, 2003
Cardiac Myocyte Stem Cells Are Found In the Mouse Heart
Torella et al., Circulation Res. 94:514, 2004
Cardiac Stem Cells and Aging: mtOxDam in Cardiac Myocytes with Normal (WT) and Elevated (TG) Levels of IGF-
1
Rep Hyp Die
Torella et al., Circulation Res. 94:514, 2004
Rep Hyp Die
Cell Senescence Markers Increase in WT but not in TG
myocytes
Telomere lengths decrease significantly more in WT than in TG myocytes
Torella et al., Circulation Res. 94:514, 2004
Deaths >>Births
Function Lost
Deaths = Births
Function Kept
TG mice with elevated IGF-1 Have Larger Numbers of Functional Cardiac Stem Cells, & Their Demographic Balance
Keeps Their Heart Functional Longer Than in WT
Torella et al., Circulation Res. 94:514, 2004
Note difference in growth kinetics & the functional effects of these different growth strategies.
Is there a contradiction between these effects of elevated IGF 1 effects on the heart & the effects of decreased IGF 1 on longevity?
Summary of the Data
Note that localized high levels of IGF-1 also maintain regenerative capacity in skeletal muscle
ROS Limits the Lifespan of Hematopoetic Cells in vivo
HSC treated in vitro with a GSH depleter (BSO) have dose-dependent increases in ROS levels
This treatment has no effect on HSC’s ability to form colonies in vitro within 1 week after treatment
This treatment has an obvious effect on the HSC’s ability to form colonies in vivo 16 wks after being injected into a mouse.
Ito et al., Nature Medicine 12:445, 2006
One way to interpret the data of the prior slide is to make the reasonable assumption that the depletion of GSH brought about by BSO pre-treatment causes oxidative damage to the telomeres.
The damaged telomeres adversely affect the replicative potential of the HSC population. The damaged cells cannot effectively replicate in an otherwise permissive environment.
Skin Senescence
The Role of Senescent Cells in Skin Aging
Young --------------??----Old
Improbable Possible Probable
What Is The Relationship Between Cell Aging & Tissue Aging?
Fossel, Cells, Aging & Human Disease, Oxford 2005
Dimri et al., PNAS 92:9363, 1995
Early Passage Late Passage
pH 4, non-specific
pH 6.0, SA-β-Gal
SA-β-Gal stained cells in culture do not engage in scheduled DNA synthesis.
Young Young + Sun
Old, ++ staining Old, +++ staining
?
SA-β-Gal Staining in Human Skin of Different Ages
Dimri et al, 1995
Severino et al., ECR 257:162
Lack of Strong Correlation Between Age & Number of Stained Cells in Human Tissue Sections
Fetal
Young Adult, ~26 y
Old Adult, ~80 y
WI38 cells + Ox Stress
SA-β-Gal Staining is Induced by Oxidative Stress As Well As By Age (?)
Severino et al., 2000
? ?
? ?
Early Passage Cells
Late Passage Cells
SA-β-Gal Staining is Induced by Culture Conditions
Conclusion: SA-β-Gal Staining is a non-specific marker of senescent cells. It is a useful but not definitive marker.
Telomere Structure
Blasco, Nat. Rev. Gen. 6:611, 2005
Histone Modification Telomeres Yields Epigenetic Regulation of Cell Cycle
These complexes of altered histones and bound telomere binding proteins yield distinctive chromatin structures which can be detected by antibody staining. This allows one to determine the telomeric status of treated and control cells.
Cell Senescence In Aging Primate Skin As Assayed By Telomere Dysfunction
Herbig et al., Science 311:1257, 2006
Reconstruction of Skin From a Suspension of Skin Cells From a 15-Day Embryonic Mouse
<< Normal Human Skin
<<Human Skin Equiv. (grown in vitro from only keratinocytes & fibroblasts )
Carasco et al., Anat. Rec. 264:261, 2001
Not an exact imitation!
From Carasco et al, Anat. Rec. 264:261:2001
Reconstituted Human Skin Expresses Appropriate Cell Differentiation Antigens
DNA Content
The Cells in the HSE Appear to Go Through The Cell Cycle In A Normal Manner
Carasco et al., Anat. Rec. 264:261, 2001
Modified HSE protocol. Took dermal fibroblasts from culture with or without pTERT, and assayed their contribution to the phenotype of reconstituted skin.
Dissociated keratinocytes were mixed with aged and treated fibroblasts in culture chambers on nude mice.
Questions being asked:
1. Does telomerase treatment affect fibroblast function?
2. Does skin structure and function correlate with functional state of fibroblasts?
PD20 PD60
PD85 PD 110 hTERT
Resistance to Mechanical Blistering of Skin With Different Fibroblasts
Funk et al, ECR 258:270, 2000
<Laminin 5
<Collagen VII
Note that skin reconstituted with young passage fibroblasts (upper fig.) and fibroblasts expressing a telomerase transgene (lower fig.) both show hemidesmosomes linked into intermediate filaments within the epidermis are positioned directly across from regions containing collagen filaments (arrows).
Also note there was no EM photo of skin reconstituted with old passage fibroblasts, although the implication of the article is that the properties of young skin are associated with fibroblast cells expressing telomerase and certain patterns of gene expression.
From Funk et al ECR 258:271, 2000
FINE STRUCTURE IS RELATED TO FIBROBLAST CELL STATE?
Funk et al, ECR 258:270, 2000
Late Cells
Early Cells
Sen/young >> hTERT/young
Young/sen ~ = hTERT/sen