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Article ; Online: How stiff is skin?

Graham, Helen K / McConnell, James C / Limbert, Georges / Sherratt, Michael J

2019 Volume 28 Suppl 1, Page(s) 4–9

Abstract: The measurement of the mechanical properties of skin (such as stiffness, extensibility and strength) is a key step in characterisation of both dermal ageing and disease mechanisms and in the assessment of tissue-engineered skin replacements. However, the ...

Abstract	The measurement of the mechanical properties of skin (such as stiffness, extensibility and strength) is a key step in characterisation of both dermal ageing and disease mechanisms and in the assessment of tissue-engineered skin replacements. However, the biomechanical terminology and plethora of mathematical analysis approaches can be daunting to those outside the field. As a consequence, mechanical studies are often inaccessible to a significant proportion of the intended audience. Furthermore, devices for the measurement of skin function in vivo generate relative values rather than formal mechanical measures, therefore limiting the ability to compare studies. In this viewpoint essay, we discuss key biomechanical concepts and the influence of technical and biological factors (including the nature of the testing apparatus, length scale, donor age and anatomical site) on measured mechanical properties such as stiffness. Having discussed the current state-of-the-art in macro-mechanical and micromechanical measuring techniques and in mathematical and computational modelling methods, we then make suggestions as to how these approaches, in combination with 3D X-ray imaging and mechanics methods, may be adopted into a single strategy to characterise the mechanical behaviour of skin.
MeSH term(s)	Age Factors ; Biomechanical Phenomena ; Computer Simulation ; Humans ; Imaging, Three-Dimensional ; Models, Theoretical ; Skin/pathology ; Skin Physiological Phenomena ; Stress, Mechanical ; Tissue Donors ; Tissue Engineering ; X-Rays
Language	English
Publishing date	2019-01-29
Publishing country	Denmark
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1130936-2
ISSN	1600-0625 ; 0906-6705
ISSN (online)	1600-0625
ISSN	0906-6705
DOI	10.1111/exd.13826
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Article ; Online: Ageing significantly impacts the biomechanical function and structural composition of skin.

Langton, Abigail K / Graham, Helen K / Griffiths, Christopher E M / Watson, Rachel E B

Experimental dermatology

2019 Volume 28, Issue 8, Page(s) 981–984

Abstract: Skin ageing is a complex process involving the additive effects of skin's interaction with its external environment, predominantly chronic sun exposure, upon a background of time-dependent intrinsic ageing. Here, using non-invasive cutometry and ... ...

Abstract	Skin ageing is a complex process involving the additive effects of skin's interaction with its external environment, predominantly chronic sun exposure, upon a background of time-dependent intrinsic ageing. Here, using non-invasive cutometry and ballistometry, we explore the consequences of ageing on the biomechanical function of skin in otherwise healthy White Northern European volunteers. Intrinsic skin ageing caused biomechanical decline; skin loses both resilience (P < 0.01) and elasticity (P < 0.001), which is characterised histologically by modest effacement of rete ridges (P < 0.05) and disorganisation of papillary dermal elastic fibres. At photoexposed sites, biomechanical testing identified significant loss of biomechanical function-particularly in the aged cohort. Photoaged forearm displayed severe loss of resilience (P < 0.001) and elasticity (P < 0.001); furthermore with repetitive testing, fatigue (P < 0.001), hysteresis (P < 0.001) and viscous "creep" (P < 0.001) were exacerbated. Histologically, both young and aged forearm displayed flattening of rete ridges and disruption to the arrangement of elastic fibres. We conclude that maintenance of skin architecture is inherently associated with optimal biomechanical properties. Modest perturbations to skin architecture-as exemplified by intrinsic ageing-result in moderate functional decline. Chronic sun exposure causes fundamental changes to the clinical and histological appearance of skin, and these are reflected by an extreme alteration in biomechanical function.
MeSH term(s)	Adult ; Aged ; Aged, 80 and over ; Biomechanical Phenomena ; Buttocks ; Female ; Forearm ; Humans ; Male ; Skin Aging ; Young Adult
Language	English
Publishing date	2019-05-28
Publishing country	Denmark
Document type	Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1130936-2
ISSN	1600-0625 ; 0906-6705
ISSN (online)	1600-0625
ISSN	0906-6705
DOI	10.1111/exd.13980
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Article ; Online: Matrix-Bound Growth Factors are Released upon Cartilage Compression by an Aggrecan-Dependent Sodium Flux that is Lost in Osteoarthritis.

Keppie, Stuart J / Mansfield, Jessica C / Tang, Xiaodi / Philp, Christopher J / Graham, Helen K / Önnerfjord, Patrik / Wall, Alanna / McLean, Celia / Winlove, C Peter / Sherratt, Michael J / Pavlovskaya, Galina E / Vincent, Tonia L

Function (Oxford, England)

2021 Volume 2, Issue 5, Page(s) zqab037

Abstract: Articular cartilage is a dense extracellular matrix-rich tissue that degrades following chronic mechanical stress, resulting in osteoarthritis (OA). The tissue has low intrinsic repair especially in aged and osteoarthritic joints. Here, we describe three ...

Abstract	Articular cartilage is a dense extracellular matrix-rich tissue that degrades following chronic mechanical stress, resulting in osteoarthritis (OA). The tissue has low intrinsic repair especially in aged and osteoarthritic joints. Here, we describe three pro-regenerative factors; fibroblast growth factor 2 (FGF2), connective tissue growth factor, bound to transforming growth factor-beta (CTGF-TGFβ), and hepatoma-derived growth factor (HDGF), that are rapidly released from the pericellular matrix (PCM) of articular cartilage upon mechanical injury. All three growth factors bound heparan sulfate, and were displaced by exogenous NaCl. We hypothesised that sodium, sequestered within the aggrecan-rich matrix, was freed by injurious compression, thereby enhancing the bioavailability of pericellular growth factors. Indeed, growth factor release was abrogated when cartilage aggrecan was depleted by IL-1 treatment, and in severely damaged human osteoarthritic cartilage. A flux in free matrix sodium upon mechanical compression of cartilage was visualised by Significance statement: Osteoarthritis is the most prevalent musculoskeletal disease, affecting 250 million people worldwide.
Language	English
Publishing date	2021-08-02
Publishing country	England
Document type	Journal Article
ISSN	2633-8823
ISSN (online)	2633-8823
DOI	10.1093/function/zqab037
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Article: Mass-mapping of ECM macromolecules by scanning transmission electron microscopy.

Sherratt, Michael J / Graham, Helen K / Kielty, Cay M / Holmes, David F

Methods in molecular biology (Clifton, N.J.)

2009 Volume 522, Page(s) 151–161

Abstract: In the scanning transmission electron microscope, the degree of electron scattering induced by biological specimens, such as ECM macromolecules, is dependent on the molecular mass. By calibrating the ratio of scattered to non-scattered electrons against ... ...

Abstract	In the scanning transmission electron microscope, the degree of electron scattering induced by biological specimens, such as ECM macromolecules, is dependent on the molecular mass. By calibrating the ratio of scattered to non-scattered electrons against a known mass standard, such as tobacco mosaic virus, it is possible to quantify absolute changes in both mass and mass distribution. These mass mapping approaches can provide important information on ECM assembly, organisation, and interactions which is not obtainable by other means.
MeSH term(s)	Extracellular Matrix Proteins/chemistry ; Microscopy, Electron, Scanning Transmission/methods ; Molecular Weight
Chemical Substances	Extracellular Matrix Proteins
Language	English
Publishing date	2009-02-27
Publishing country	United States
Document type	Journal Article
ISSN	1064-3745
ISSN	1064-3745
DOI	10.1007/978-1-59745-413-1_9
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Article: ECM macromolecules: rotary shadowing and transmission electron microscopy.

Sherratt, Michael J / Meadows, Roger S / Graham, Helen K / Kielty, Cay M / Holmes, David F

Methods in molecular biology (Clifton, N.J.)

2009 Volume 522, Page(s) 175–181

Abstract: Conventional preparation techniques for electron microscopy employ contrast enhancing heavy metal stains in solution to visualize isolated macromolecules. In rotary shadowing electron microscopy, the heavy metal is evaporated onto surface adsorbed ... ...

Abstract	Conventional preparation techniques for electron microscopy employ contrast enhancing heavy metal stains in solution to visualize isolated macromolecules. In rotary shadowing electron microscopy, the heavy metal is evaporated onto surface adsorbed molecules and macromolecular assemblies. High resolution shadowing remains a valuable method for the visualization and characterization of extracellular matrix macromolecules including fibrillar collagens, microfibrillar elements, and glycoproteins.
MeSH term(s)	Collagen/chemistry ; Extracellular Matrix Proteins/ultrastructure ; Fibrillins ; Microfilament Proteins/ultrastructure ; Microscopy, Electron, Transmission/methods
Chemical Substances	Extracellular Matrix Proteins ; Fibrillins ; Microfilament Proteins ; Collagen (9007-34-5)
Language	English
Publishing date	2009-02-27
Publishing country	United States
Document type	Journal Article
ISSN	1064-3745
ISSN	1064-3745
DOI	10.1007/978-1-59745-413-1_11
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Article ; Online: Localised micro-mechanical stiffening in the ageing aorta.

Graham, Helen K / Akhtar, Riaz / Kridiotis, Constantinos / Derby, Brian / Kundu, Tribikram / Trafford, Andrew W / Sherratt, Michael J

Mechanisms of ageing and development

2011 Volume 132, Issue 10, Page(s) 459–467

Abstract: Age-related loss of tissue elasticity is a common cause of human morbidity and arteriosclerosis (vascular stiffening) is associated with the development of both fatal strokes and heart failure. However, in the absence of appropriate micro-mechanical ... ...

Abstract	Age-related loss of tissue elasticity is a common cause of human morbidity and arteriosclerosis (vascular stiffening) is associated with the development of both fatal strokes and heart failure. However, in the absence of appropriate micro-mechanical testing methodologies, multiple structural remodelling events have been proposed as the cause of arteriosclerosis. Therefore, using a model of ageing in female sheep aorta (young: <18 months, old: >8 years) we: (i) quantified age-related macro-mechanical stiffness, (ii) localised in situ micro-metre scale changes in acoustic wave speed (a measure of tissue stiffness) and (iii) characterised collagen and elastic fibre remodelling. With age, there was an increase in both macro-mechanical stiffness and mean microscopic wave speed (and hence stiffness; young wave speed: 1701±1ms(-1), old wave speed: 1710±1ms(-1), p<0.001) which was localized to collagen fibril-rich regions located between large elastic lamellae. These micro-mechanical changes were associated with increases in both collagen and elastic fibre content (collagen tissue area, young: 31±2%, old: 40±4%, p<0.05; elastic fibre tissue area, young: 55±3%, old: 69±4%, p<0.001). Localised collagen fibrosis may therefore play a key role in mediating age-related arteriosclerosis. Furthermore, high frequency scanning acoustic microscopy is capable of co-localising micro-mechanical and micro-structural changes in ageing tissues.
MeSH term(s)	Aging/pathology ; Aging/physiology ; Animals ; Aorta/pathology ; Aorta/physiopathology ; Biomechanical Phenomena ; Elastic Tissue/pathology ; Elastic Tissue/physiopathology ; Elasticity/physiology ; Extracellular Matrix/pathology ; Extracellular Matrix/physiology ; Female ; Microscopy, Acoustic ; Sheep ; Vascular Stiffness/physiology
Language	English
Publishing date	2011-07-12
Publishing country	Ireland
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	183915-9
ISSN	1872-6216 ; 0047-6374
ISSN (online)	1872-6216
ISSN	0047-6374
DOI	10.1016/j.mad.2011.07.003
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Zs.A 1012: Show issues

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Article ; Online: Perturbed atrial calcium handling in an ovine model of heart failure: potential roles for reductions in the L-type calcium current.

Clarke, Jessica D / Caldwell, Jessica L / Horn, Margaux A / Bode, Elizabeth F / Richards, Mark A / Hall, Mark C S / Graham, Helen K / Briston, Sarah J / Greensmith, David J / Eisner, David A / Dibb, Katharine M / Trafford, Andrew W

Journal of molecular and cellular cardiology

2014 Volume 79, Page(s) 169–179

Abstract: Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca(2+) and the response ... ...

Abstract	Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca(2+) and the response to β-adrenergic (β-AR) stimulation in atrial myocytes. HF was induced in sheep by ventricular tachypacing and changes in intracellular Ca(2+) concentration studied in single left atrial myocytes under voltage and current clamp conditions. The following were all reduced in HF atrial myocytes; Ca(2+) transient amplitude (by 46% in current clamped and 28% in voltage clamped cells), SR dependent rate of Ca(2+) removal (kSR, by 32%), L-type Ca(2+) current density (by 36%) and action potential duration (APD90 by 22%). However, in HF SR Ca(2+) content was increased (by 19%) when measured under voltage-clamp stimulation. Inhibiting the L-type Ca(2+) current (ICa-L) in control cells reproduced both the decrease in Ca(2+) transient amplitude and increase of SR Ca(2+) content observed in voltage-clamped HF cells. During β-AR stimulation Ca(2+) transient amplitude was the same in control and HF cells. However, ICa-L remained less in HF than control cells whilst SR Ca(2+) content was highest in HF cells during β-AR stimulation. The decrease in ICa-L that occurs in HF atrial myocytes appears to underpin the decreased Ca(2+) transient amplitude and increased SR Ca(2+) content observed in voltage-clamped cells.
MeSH term(s)	Action Potentials ; Animals ; Calcium/metabolism ; Calcium Channels, L-Type/metabolism ; Disease Models, Animal ; Female ; Heart Atria/metabolism ; Heart Atria/pathology ; Heart Failure/metabolism ; Heart Failure/pathology ; Homeostasis ; Intracellular Space/metabolism ; Ion Channel Gating ; Models, Biological ; Receptors, Adrenergic, beta/metabolism ; Sarcoplasmic Reticulum/metabolism ; Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism ; Sheep ; Systole
Chemical Substances	Calcium Channels, L-Type ; Receptors, Adrenergic, beta ; Sarcoplasmic Reticulum Calcium-Transporting ATPases (EC 3.6.3.8) ; Calcium (SY7Q814VUP)
Language	English
Publishing date	2014-11-22
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	80157-4
ISSN	1095-8584 ; 0022-2828
ISSN (online)	1095-8584
ISSN	0022-2828
DOI	10.1016/j.yjmcc.2014.11.017
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Article ; Online: Characterization of an extensive transverse tubular network in sheep atrial myocytes and its depletion in heart failure.

Dibb, Katharine M / Clarke, Jessica D / Horn, Margaux A / Richards, Mark A / Graham, Helen K / Eisner, David A / Trafford, Andrew W

Circulation. Heart failure

2009 Volume 2, Issue 5, Page(s) 482–489

Abstract: Background: In ventricular myocytes, the majority of structures that couple excitation to the systolic rise of Ca(2+) are located at the transverse tubular (t-tubule) membrane. In the failing ventricle, disorganization of t-tubules disrupts excitation ... ...

Abstract	Background: In ventricular myocytes, the majority of structures that couple excitation to the systolic rise of Ca(2+) are located at the transverse tubular (t-tubule) membrane. In the failing ventricle, disorganization of t-tubules disrupts excitation contraction coupling. The t-tubule membrane is virtually absent in the atria of small mammals resulting in spatiotemporally distinct profiles of intracellular Ca(2+) release on stimulation in atrial and ventricular cells. The aims of this study were to determine (i) whether atrial myocytes from a large mammal (sheep) possess t-tubules, (ii) whether these are functionally important, and (iii) whether they are disrupted in heart failure. Methods and results: Sheep left atrial myocytes were stained with di-4-ANEPPS. Nearly all control cells had an extensive t-tubule network resulting in each voxel in the cell being nearer to a membrane (sarcolemma or t-tubule) than would otherwise be the case. T-tubules decrease the distance of 50% of voxels from a membrane from 3.35 + or - 0.15 to 0.88 + or- 0.04 microm. During depolarization, intracellular Ca(2+) rises simultaneously at the cell periphery and center. In heart failure induced by rapid ventricular pacing, there was an almost complete loss of atrial t-tubules. The distance of 50% of voxels from a membrane increased to 2.04 + or - 0.08 microm, and there was a loss of early Ca(2+) release from the cell center. Conclusions: Sheep atrial myocytes possess a substantial t-tubule network that synchronizes the systolic Ca(2+) transient. In heart failure, this network is markedly disrupted. This may play an important role in changes of atrial function in heart failure.
MeSH term(s)	Animals ; Atrial Function, Left ; Calcium Signaling ; Cardiac Pacing, Artificial ; Disease Models, Animal ; Fluorescent Dyes ; Heart Atria/metabolism ; Heart Failure/metabolism ; Heart Failure/pathology ; Heart Failure/physiopathology ; Image Processing, Computer-Assisted ; Microscopy, Confocal ; Myocardial Contraction ; Myocytes, Cardiac/metabolism ; Myocytes, Cardiac/pathology ; Pyridinium Compounds ; Rats ; Sarcolemma/metabolism ; Sarcolemma/pathology ; Sheep ; Ventricular Function, Left
Chemical Substances	Fluorescent Dyes ; Pyridinium Compounds ; 1-(3-sulfonatopropyl)-4-(beta)(2-(di-n-butylamino)-6-naphthylvinyl)pyridinium betaine (90134-00-2)
Language	English
Publishing date	2009-07-29
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2429459-7
ISSN	1941-3297 ; 1941-3289
ISSN (online)	1941-3297
ISSN	1941-3289
DOI	10.1161/CIRCHEARTFAILURE.109.852228
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Article ; Online: Age-related divergent remodeling of the cardiac extracellular matrix in heart failure: collagen accumulation in the young and loss in the aged.

Horn, Margaux A / Graham, Helen K / Richards, Mark A / Clarke, Jessica D / Greensmith, David J / Briston, Sarah J / Hall, Mark C S / Dibb, Katharine M / Trafford, Andrew W

Journal of molecular and cellular cardiology

2012 Volume 53, Issue 1, Page(s) 82–90

Abstract: The incidence of heart failure (HF) increases with age. This study sought to determine whether aging exacerbates structural and functional remodeling of the myocardium in HF. HF was induced in young (~18 months) and aged sheep (>8 years) by right ... ...

Abstract	The incidence of heart failure (HF) increases with age. This study sought to determine whether aging exacerbates structural and functional remodeling of the myocardium in HF. HF was induced in young (~18 months) and aged sheep (>8 years) by right ventricular tachypacing. In non-paced animals, aging was associated with increased left ventricular (LV) end diastolic internal dimensions (EDID, P<0.001), reduced fractional shortening (P<0.01) and an increase in myocardial collagen content (P<0.01). HF increased EDID and reduced fractional shortening in both young and aged animals, although these changes were more pronounced in the aged (P<0.05). Age-associated differences in cardiac extracellular matrix (ECM) remodeling occurred in HF with collagen accumulation in young HF (P<0.001) and depletion in aged HF (P<0.05). MMP-2 activity increased in the aged control and young HF groups (P<0.05). Reduced tissue inhibitor of metalloproteinase (TIMP) expression (TIMPs 3 and 4, P<0.05) was present only in the aged HF group. Secreted protein acidic and rich in cysteine (SPARC) was increased in aged hearts compared to young controls (P<0.05) while serum procollagen type I C-pro peptide (PICP) was increased in both young failing (P<0.05) and aged failing (P<0.01) animals. In conclusion, collagen content of the cardiac ECM changes in both aging and HF although; whether collagen accumulation or depletion occurs depends on age. Changes in TIMP expression in aged failing hearts alongside augmented collagen synthesis in HF provide a potential mechanism for the age-dependent ECM remodeling. Aging should therefore be considered an important factor when elucidating cardiac disease mechanisms.
MeSH term(s)	Age Factors ; Animals ; Collagen/metabolism ; Disease Models, Animal ; Endomyocardial Fibrosis/metabolism ; Extracellular Matrix/metabolism ; Female ; Heart/physiopathology ; Heart Failure/metabolism ; Myocardial Contraction ; Myocardium/metabolism ; Sheep ; Tissue Inhibitor of Metalloproteinases/metabolism ; Ventricular Remodeling
Chemical Substances	Tissue Inhibitor of Metalloproteinases ; Collagen (9007-34-5)
Language	English
Publishing date	2012-03-30
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	80157-4
ISSN	1095-8584 ; 0022-2828
ISSN (online)	1095-8584
ISSN	0022-2828
DOI	10.1016/j.yjmcc.2012.03.011
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Article ; Online: Impaired β-adrenergic responsiveness accentuates dysfunctional excitation-contraction coupling in an ovine model of tachypacing-induced heart failure.

Briston, Sarah J / Caldwell, Jessica L / Horn, Margaux A / Clarke, Jessica D / Richards, Mark A / Greensmith, David J / Graham, Helen K / Hall, Mark C S / Eisner, David A / Dibb, Katharine M / Trafford, Andrew W

The Journal of physiology

2011 Volume 589, Issue Pt 6, Page(s) 1367–1382

Abstract: Reduced inotropic responsiveness is characteristic of heart failure (HF). This study determined the cellular Ca2+ homeostatic and molecular mechanisms causing the blunted β-adrenergic (β-AR) response in HF.We induced HF by tachypacing in sheep; ... ...

Abstract	Reduced inotropic responsiveness is characteristic of heart failure (HF). This study determined the cellular Ca2+ homeostatic and molecular mechanisms causing the blunted β-adrenergic (β-AR) response in HF.We induced HF by tachypacing in sheep; intracellular Ca2+ concentration was measured in voltage-clamped ventricular myocytes. In HF, Ca2+ transient amplitude and peak L-type Ca2+ current (ICa-L) were reduced (to 70 ± 11% and 50 ± 3.7% of control, respectively, P <0.05) whereas sarcoplasmic reticulum (SR) Ca2+ content was unchanged. β-AR stimulation with isoprenaline (ISO) increased Ca2+ transient amplitude, ICa-L and SRCa2+ content in both cell types; however, the response of HF cells was markedly diminished (P <0.05).Western blotting revealed an increase in protein phosphatase levels (PP1, 158 ± 17% and PP2A, 188 ± 34% of control, P <0.05) and reduced phosphorylation of phospholamban in HF (Ser16, 30 ± 10% and Thr17, 41 ± 15% of control, P <0.05). The β-AR receptor kinase GRK-2 was also increased in HF (173 ± 38% of control, P <0.05). In HF, activation of adenylyl cyclase with forskolin rescued the Ca2+ transient, SR Ca2+ content and SR Ca2+ uptake rate to the same levels as control cells in ISO. In conclusion, the reduced responsiveness of the myocardium to β-AR agonists in HF probably arises as a consequence of impaired phosphorylation of key intracellular proteins responsible for regulating the SR Ca2+ content and therefore failure of the systolic Ca2+ transient to increase appropriately during β-AR stimulation.
MeSH term(s)	Animals ; Disease Models, Animal ; Excitation Contraction Coupling/physiology ; Female ; Heart Failure/etiology ; Heart Failure/physiopathology ; Myocardial Contraction/physiology ; Receptors, Adrenergic, beta/physiology ; Sheep ; Tachycardia, Ventricular/complications ; Tachycardia, Ventricular/physiopathology
Chemical Substances	Receptors, Adrenergic, beta
Language	English
Publishing date	2011-01-17
Publishing country	England
Document type	Comparative Study ; Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	3115-x
ISSN	1469-7793 ; 0022-3751
ISSN (online)	1469-7793
ISSN	0022-3751
DOI	10.1113/jphysiol.2010.203984
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