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Lin CY, Sugerman GP, Kakaletsis S, Meador WD, Buganza AT, Rausch MK. Sex- and age-dependent skin mechanics-A detailed look in mice. Acta Biomater 2024; 175:106-113. [PMID: 38042263 DOI: 10.1016/j.actbio.2023.11.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 10/28/2023] [Accepted: 11/21/2023] [Indexed: 12/04/2023]
Abstract
Skin aging is of immense societal and, thus, scientific interest. Because mechanics play a critical role in skin's function, a plethora of studies have investigated age-induced changes in skin mechanics. Nonetheless, much remains to be learned about the mechanics of aging skin. This is especially true when considering sex as a biological variable. In our work, we set out to answer some of these questions using mice as a model system. Specifically, we combined mechanical testing, histology, collagen assays, and two-photon microscopy to identify age- and sex-dependent changes in skin mechanics and to relate them to structural, microstructural, and compositional factors. Our work revealed that skin stiffness, thickness, and collagen content all decreased with age and were sex dependent. Interestingly, sex differences in stiffness were age induced. We hope our findings not only further our fundamental understanding of skin aging but also highlight both age and sex as important variables when conducting studies on skin mechanics. STATEMENT OF SIGNIFICANCE: Our work addresses the question, "How do sex and age affect the mechanics of skin?" Answering this question is of both scientific and societal importance. We do so in mice as a model system. Thereby, we hope to add clarity to a body of literature that appears divided on the effect of both factors. Our findings have important implications for those studying age and sex differences, especially in mice as a model system.
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Affiliation(s)
- Chien-Yu Lin
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Gabriella P Sugerman
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Sotirios Kakaletsis
- Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, TX, USA
| | - William D Meador
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Adrian T Buganza
- Department of Mechanical Engineering, Purdue University, West Lafayette, IN, USA
| | - Manuel K Rausch
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, USA; Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, TX, USA; Oden Institute for Computational Engineering & Sciences, The University of Texas at Austin, Austin, TX, USA.
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Siess M, Steinke H, Zwirner J, Hammer N. On a potential morpho-mechanical link between the gluteus maximus muscle and pelvic floor tissues. Sci Rep 2023; 13:22901. [PMID: 38129498 PMCID: PMC10739724 DOI: 10.1038/s41598-023-50058-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 12/14/2023] [Indexed: 12/23/2023] Open
Abstract
Stress urinary incontinence presents a condition not only found in female elderlies, but also in young athletes participating in high-impact sports such as volleyball or trampolining. Repeated jumps appear to be a predisposing factor. Yet the pathophysiology remains incompletely elucidated to date; especially with regard to the influence of the surrounding buttock tissues including gluteus maximus. The present study assessed the morpho-mechanical link between gluteus maximus and the pelvic floor female bodies. 25 pelves obtained from Thiel embalmed females were studied in a supine position. Strands of tissues connecting gluteus maximus with the pelvic floor obtained from 20 sides were assessed mechanically. Plastinates were evaluated to verify the dissection findings. In total, 49 hemipelves were included for data acquisition. The fascia of gluteus maximus yielded connections to the subcutaneous tissues, the fascia of the external anal sphincter and that of obturator internus and to the fascia of the urogenital diaphragm. The connection between gluteus maximus and the urogenital diaphragm withstood an average force of 23.6 ± 17.3 N. Cramér φ analyses demonstrated that the connections of the fasciae connecting gluteus maximus with its surroundings were consistent in the horizontal and sagittal planes, respectively. In conclusion, gluteus maximus is morphologically densely linked to the pelvic floor via strands of connective tissues investing the adjacent muscles. Though gluteus maximus has also been reported to facilitate urinary continence, the here presented morpho-mechanical link suggests that it may also have the potential to contribute to urinary stress incontinence. Future research combining clinical imaging with in-situ testing may help substantiate the potential influence from a clinical perspective.
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Affiliation(s)
- Maximilian Siess
- Division of Macroscopic and Clinical Anatomy, Gottfried Schatz Research Center, Medical University of Graz, Auenbruggerplatz 25, 8036, Graz, Austria
| | - Hanno Steinke
- Institute of Anatomy, University of Leipzig, Leipzig, Germany
| | - Johann Zwirner
- Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Niels Hammer
- Division of Macroscopic and Clinical Anatomy, Gottfried Schatz Research Center, Medical University of Graz, Auenbruggerplatz 25, 8036, Graz, Austria.
- Department of Orthopedic and Trauma Surgery, University of Leipzig, Leipzig, Germany.
- Medical Branch, Fraunhofer Institute for Machine Tools and Forming Technology (IWU), Chemnitz, Germany.
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Kriener K, Whiting H, Storr N, Homes R, Lala R, Gabrielyan R, Kuang J, Rubin B, Frails E, Sandstrom H, Futter C, Midwinter M. Applied use of biomechanical measurements from human tissues for the development of medical skills trainers: a scoping review. JBI Evid Synth 2023; 21:2309-2405. [PMID: 37732940 DOI: 10.11124/jbies-22-00363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
OBJECTIVE The objective of this review was to identify quantitative biomechanical measurements of human tissues, the methods for obtaining these measurements, and the primary motivations for conducting biomechanical research. INTRODUCTION Medical skills trainers are a safe and useful tool for clinicians to use when learning or practicing medical procedures. The haptic fidelity of these devices is often poor, which may be because the synthetic materials chosen for these devices do not have the same mechanical properties as human tissues. This review investigates a heterogeneous body of literature to identify which biomechanical properties are available for human tissues, the methods for obtaining these values, and the primary motivations behind conducting biomechanical tests. INCLUSION CRITERIA Studies containing quantitative measurements of the biomechanical properties of human tissues were included. Studies that primarily focused on dynamic and fluid mechanical properties were excluded. Additionally, studies only containing animal, in silico , or synthetic materials were excluded from this review. METHODS This scoping review followed the JBI methodology for scoping reviews and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR). Sources of evidence were extracted from CINAHL (EBSCO), IEEE Xplore, MEDLINE (PubMed), Scopus, and engineering conference proceedings. The search was limited to the English language. Two independent reviewers screened titles and abstracts as well as full-text reviews. Any conflicts that arose during screening and full-text review were mediated by a third reviewer. Data extraction was conducted by 2 independent reviewers and discrepancies were mediated through discussion. The results are presented in tabular, figure, and narrative formats. RESULTS Data were extracted from a total of 186 full-text publications. All of the studies, except for 1, were experimental. Included studies came from 33 countries, with the majority coming from the United States. Ex vivo methods were the predominant approach for extracting human tissue samples, and the most commonly studied tissue type was musculoskeletal. In this study, nearly 200 unique biomechanical values were reported, and the most commonly reported value was Young's (elastic) modulus. The most common type of mechanical test performed was tensile testing, and the most common reason for testing human tissues was to characterize biomechanical properties. Although the number of published studies on biomechanical properties of human tissues has increased over the past 20 years, there are many gaps in the literature. Of the 186 included studies, only 7 used human tissues for the design or validation of medical skills training devices. Furthermore, in studies where biomechanical values for human tissues have been obtained, a lack of standardization in engineering assumptions, methodologies, and tissue preparation may implicate the usefulness of these values. CONCLUSIONS This review is the first of its kind to give a broad overview of the biomechanics of human tissues in the published literature. With respect to high-fidelity haptics, there is a large gap in the published literature. Even in instances where biomechanical values are available, comparing or using these values is difficult. This is likely due to the lack of standardization in engineering assumptions, testing methodology, and reporting of the results. It is recommended that journals and experts in engineering fields conduct further research to investigate the feasibility of implementing reporting standards. REVIEW REGISTRATION Open Science Framework https://osf.io/fgb34.
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Affiliation(s)
- Kyleigh Kriener
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Harrison Whiting
- Department of Anaesthesia and Perioperative Medicine, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia
- School of Clinical Medicine, Royal Brisbane Clinical Unit, The University of Queensland, Brisbane, QLD, Australia
| | - Nicholas Storr
- Gold Coast University Hospital, Southport, QLD Australia
| | - Ryan Homes
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Raushan Lala
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Robert Gabrielyan
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Ochsner Clinical School, Jefferson, LA, United States
| | - Jasmine Kuang
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Ochsner Clinical School, Jefferson, LA, United States
| | - Bryn Rubin
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Ochsner Clinical School, Jefferson, LA, United States
| | - Edward Frails
- Department of Chemical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Hannah Sandstrom
- Department of Exercise Science and Sport Management, Kennesaw State University, Kennesaw, GA, United States
| | - Christopher Futter
- Department of Anaesthesia and Perioperative Medicine, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia
- Anaesthesia and Intensive Care Program, Herston Biofabrication institute, Brisbane, QLD, Australia
| | - Mark Midwinter
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
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Hammer N, Ondruschka B, Berghold A, Kuenzer T, Pregartner G, Scholze M, Schulze-Tanzil GG, Zwirner J. Sample size considerations in soft tissue biomechanics. Acta Biomater 2023; 169:168-178. [PMID: 37517620 DOI: 10.1016/j.actbio.2023.07.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 07/12/2023] [Accepted: 07/23/2023] [Indexed: 08/01/2023]
Abstract
Biomechanical experiments help link tissue morphology with load-deformation characteristics. A tissue-dependent minimum sample number is indispensable to obtain accurate material properties. Stress-strain properties were retrieved from human dura mater and scalp skin, exemplifying two distinct soft tissues. Minimum sample sizes necessary for a stable estimation of material properties were obtained in a simulation study. One-thousand random samples were sequentially drawn for calculating the point at which a majority of the estimators settled within a corridor of stability at given tolerance levels around a 'complete' reference for the mean, median and coefficient of variation. Stable estimations of means and medians can be achieved below sample sizes of 30 at a ± 20%-tolerance within 80%-conformity for scalp skin and dura. Lower tolerance levels or higher conformity dramatically increase the required sample size. Conformity was barely ever reached for the coefficient of variation. The parameter type appears decisive for achieving conformity. STATEMENT OF SIGNIFICANCE: Biomechanical trials utilizing human tissues are needed to obtain material properties for surgical repair, tissue engineering and modeling purposes. Linking tissue mechanics with morphology helps elucidate form-function relationships, the 'morpho-mechanical link'. For material properties to be accurate, it is vital to examine a minimum number of samples. This number may vary between tissues, and the effects of intrinsic tissue characteristics on data accuracy are unclear to date. This study used data obtained from human dura and skin to compute minimum sample sizes required for estimating material properties at a stable level. It was shown that stable estimations are possible at a ± 20%-tolerance within 80%-conformity below sample sizes of 30. Higher accuracy warrants much higher sample sizes for most material properties.
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Affiliation(s)
- Niels Hammer
- Division of Macroscopic and Clinical Anatomy, Gottfried Schatz Research Center, Medical University of Graz, Graz, Austria; Department of Orthopedic and Trauma Surgery, University of Leipzig, Leipzig, Germany; Division of Biomechatronics, Fraunhofer Institute for Machine Tools and Forming Technology Dresden, Germany.
| | - Benjamin Ondruschka
- Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Andrea Berghold
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz, Austria
| | - Thomas Kuenzer
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz, Austria
| | - Gudrun Pregartner
- Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Graz, Austria
| | - Mario Scholze
- Institute of Materials Science and Engineering, Chemnitz University of Technology, Chemnitz, Germany
| | | | - Johann Zwirner
- Institute of Legal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Department of Oral Sciences, University of Otago, Dunedin, New Zealand
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Lin CY, Sugerman GP, Kakaletsis S, Meador WD, Buganza AT, Rausch MK. Sex- and Age-dependent Skin Mechanics - A Detailed Look in Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.08.531781. [PMID: 36945509 PMCID: PMC10028869 DOI: 10.1101/2023.03.08.531781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
Skin aging is of immense societal and, thus, scientific interest. Because mechanics play a critical role in skin's function, a plethora of studies have investigated age-induced changes in skin mechanics. Nonetheless, much remains to be learned about the mechanics of aging skin. This is especially true when considering sex as a biological variable. In our work, we set out to answer some of these questions using mice as a model system. Specifically, we combined mechanical testing, histology, collagen assays, and two-photon microscopy to identify age- and sex-dependent changes in skin mechanics and to relate them to structural, microstructural, and compositional factors. Our work revealed that skin stiffness, thickness, and collagen content all decreased with age and were sex dependent. Interestingly, sex differences in stiffness were age induced. We hope our findings not only further our fundamental understanding of skin aging but also highlight both age and sex as important variables when conducting studies on skin mechanics.
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Affiliation(s)
- Chien-Yu Lin
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, USA
| | - Gabriella P Sugerman
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, USA
| | - Sotirios Kakaletsis
- Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, Texas, USA
| | - William D Meador
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, USA
| | - Adrian T Buganza
- Department of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Manuel K Rausch
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, USA
- Department of Aerospace Engineering & Engineering Mechanics, The University of Texas at Austin, Austin, Texas, USA
- Oden Institute for Computational Engineering & Sciences, The University of Texas at Austin, Austin, Texas, USA
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