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 PD85PD 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