Transcript Supplement 12-1 - Biological Sciences Home

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
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
Epel et al., PNAS 101: 17312, 2005
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
Rep
Hyp
Die
Torella et al., Circulation Res. 94:514, 2004
Torella et al., Circulation Res. 94:514, 2004
Cell Senescence Markers
Increase in WT but not in TG
myocytes
Telomere lengths decrease significantly
more in WT than in TG myocytes
Note
difference
in growth
kinetics &
the
functional
effects of
these
different
growth
strategies
.
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
Summary of the Data
Is there a contradiction between these effects of elevated IGF 1
effects on the heart & the effects of decreased IGF 1 on longevity?
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 dosedependent
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 pretreatment 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
What Is The Relationship Between Cell
Aging & Tissue Aging?
Improbable
Possible
Probable
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
SA-β-Gal Staining is Induced by Oxidative Stress As Well As By Age (?)
Young Adult,
~26 y
?
?
Old Adult,
~80 y
WI38 cells + Ox Stress
?
?
Fetal
Severino et al., 2000
SA-β-Gal Staining is Induced by Culture Conditions
Early Passage
Cells
Late Passage
Cells
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 )
Not an exact imitation!
Carasco et al., Anat. Rec. 264:261, 2001
Reconstituted Human Skin Expresses Appropriate Cell Differentiation Antigens
From Carasco et al, Anat. Rec. 264:261:2001
The Cells in the HSE Appear to Go Through The Cell Cycle In A
Normal Manner
DNA Content
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?
Resistance to Mechanical Blistering of Skin With Different Fibroblasts
PD20
PD60
<Laminin 5
<Collagen VII
PD85
PD 110 hTERT
Funk et al, ECR 258:270, 2000
FINE STRUCTURE IS RELATED
TO FIBROBLAST CELL STATE?
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
Late Cells
Sen/young >> hTERT/young
Early Cells
Young/sen ~ = hTERT/sen
Funk et al, ECR 258:270, 2000