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Biomechanical changes in myopic sclera correlate with underlying changes in microstructure. Exp Eye Res 2022; 224:109165. [PMID: 35810771 DOI: 10.1016/j.exer.2022.109165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/20/2022] [Accepted: 06/23/2022] [Indexed: 11/21/2022]
Abstract
Myopia alters the microstructural and biomechanical properties of the posterior sclera, which is characterized as a layered structure with potentially different inter-layer collagen fibril characteristics. Scanning acoustic microscopy (SAM) has been used to investigate how the micron-scale bulk mechanical properties of the posterior sclera are affected by myopia. Other investigators have employed second harmonic generation (SHG) imaging to characterize the collagen microstructure of tissues. In the present study, SAM and SHG imaging were used to investigate the existence of biomechanically-distinct scleral layers and identify relationships between mechanical properties and tissue microstructure in myopic guinea pig (GP) eyes. Diffusers were worn over the right eyes of six, 1-week-old GPs for one week to induce unilateral form-deprivation myopia. GPs were euthanized, enucleated, and eyes were cryosectioned. Twelve-micron-thick adjacent vertical cryosections were scanned with SAM or SHG. SAM maps of bulk modulus, mass density, and acoustic attenuation were estimated. A fiber-extraction algorithm applied to SHG images estimated collagen fiber length, width, straightness, alignment, and number density. Results revealed that the posterior sclera may exhibit biomechanically distinct layers that are affected differently in myopia. Specifically, a layered structure was observed in the mechanical-parameter maps of control eyes that was less apparent in myopic eyes. Collagen fibers in myopic eyes had smaller diameters and were more aligned. Myopia-associated biomechanical changes were most significant in the outermost and innermost scleral layers. SAM-measured mechanical parameters were correlated with collagen fiber microstructure, particularly fiber length, alignment, and number density, which may imply the biomechanical parameters estimated from SAM measurements are related to tissue microstructure. Interestingly, some changes were greatest in more-peripheral regions, suggesting interventions to strengthen the sclera may be effective away from the optic nerve and efficacy may be achieved best when intervention is applied to the outermost layer.
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Avetisov SE, Osipyan GA, Abukerimova AK, Akovantseva AA, Efremov YM, Frolova AA, Kotova SL, Timashev PS. [Experimental studies of the biomechanical properties of the cornea]. Vestn Oftalmol 2022; 138:124-131. [PMID: 35801891 DOI: 10.17116/oftalma2022138031124] [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] [Indexed: 06/15/2023]
Abstract
The review presents the results of experimental studies of the biomechanical properties of the cornea. Selective evaluation of the individual corneal structures (for example, limiting membranes) using classical mechanical tests is to a certain extent limited due to the rather small thickness of these structures and the related difficulties in sample fixation. In real practice, the use of a method better adapted for conducting such studies - atomic force microscopy (AFM) - remains promising, since on the one hand it eliminates the need for mechanical capture and retention of the sample, and on the other - provides the capability for studying its segments separately.
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Affiliation(s)
- S E Avetisov
- I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
- Research Institute of Eye Diseases, Moscow, Russia
| | - G A Osipyan
- Research Institute of Eye Diseases, Moscow, Russia
| | | | - A A Akovantseva
- Institute of Photonic Technologies of the Crystallography and Photonics Research Center, Moscow, Russia
| | - Yu M Efremov
- Institute of Regenerative Medicine of the I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - A A Frolova
- Digital Biodesign and Personalized Healthcare Center of the I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - S L Kotova
- Institute of Regenerative Medicine of the I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
- N.N. Semenov Federal Research Center for Chemical Physics, Moscow, Russia
| | - P S Timashev
- Institute of Regenerative Medicine of the I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
- Digital Biodesign and Personalized Healthcare Center of the I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
- N.N. Semenov Federal Research Center for Chemical Physics, Moscow, Russia
- Lomonosov Moscow State University, Moscow, Russia
- Institute of Photonic Technologies of the Crystallography and Photonics Research Center, Moscow, Russia
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Lamiré LA, Milani P, Runel G, Kiss A, Arias L, Vergier B, de Bossoreille S, Das P, Cluet D, Boudaoud A, Grammont M. Gradient in cytoplasmic pressure in germline cells controls overlying epithelial cell morphogenesis. PLoS Biol 2020; 18:e3000940. [PMID: 33253165 PMCID: PMC7703951 DOI: 10.1371/journal.pbio.3000940] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 10/13/2020] [Indexed: 12/31/2022] Open
Abstract
It is unknown how growth in one tissue impacts morphogenesis in a neighboring tissue. To address this, we used the Drosophila ovarian follicle, in which a cluster of 15 nurse cells and a posteriorly located oocyte are surrounded by a layer of epithelial cells. It is known that as the nurse cells grow, the overlying epithelial cells flatten in a wave that begins in the anterior. Here, we demonstrate that an anterior to posterior gradient of decreasing cytoplasmic pressure is present across the nurse cells and that this gradient acts through TGFβ to control both the triggering and the progression of the wave of epithelial cell flattening. Our data indicate that intrinsic nurse cell growth is important to control proper nurse cell pressure. Finally, we reveal that nurse cell pressure and subsequent TGFβ activity in the stretched cells combine to increase follicle elongation in the anterior, which is crucial for allowing nurse cell growth and pressure control. More generally, our results reveal that during development, inner cytoplasmic pressure in individual cells has an important role in shaping their neighbors.
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Affiliation(s)
- Laurie-Anne Lamiré
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Pascale Milani
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Gaël Runel
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Annamaria Kiss
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - Leticia Arias
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Blandine Vergier
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Stève de Bossoreille
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Pradeep Das
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - David Cluet
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Arezki Boudaoud
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - Muriel Grammont
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
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Swain A, Begam N, Chandran S, Bobji MS, Basu JK. Engineering interfacial entropic effects to generate giant viscosity changes in nanoparticle embedded polymer thin films. SOFT MATTER 2020; 16:4065-4073. [PMID: 32286599 DOI: 10.1039/d0sm00019a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Thin polymer and polymer nanocomposite (PNC) films are being extensively used as advanced functional coating materials in various technological applications. Since it is widely known that various properties of these thin films, especially their thermo-mechanical behavior, can be considerably different from the bulk depending on the thickness as well as interaction with surrounding media, it is imperative to study these properties directly on the films. However, quite often, it becomes difficult to perform these measurements reliably due to a dearth of techniques, especially to measure mechnical or transport properties like the viscosity of thin polymer or PNC films. Here, we demonstrate a new method to study the viscosity of PNC thin films using atomic force microscopy based force-distance spectroscopy. Using this method we investigated viscosity and the glass transition, Tg, of PNC thin films consisting of polymer grafted nanoparticles (PGNPs) embedded in un-entangled homopolymer melt films. The PGNP-polymer interfacial entropic interaction parameter, f, operationally controlled through the ratio of grafted and matrix molecular weight, was systematically tuned while maintaining good dispersion even at very high PGNP loadings, φ. We observed both a significant reduction (low f) and giant enhancement (high f) in the viscosity of the PNC thin films with the effect becoming more prominent with increasing φ. Significantly, none of the established theoretical models for viscosity changes observed earlier in suspensions or polymer nanocomposites can explain the observed viscosity variation. Our results thus not only demonstrate the tunability of the interfacial entropic effect to facilitate a dramatic change in the viscosity of PNC coatings, which could be of great utility in various applications of these materials, but also suggest a new regime of viscosity variation in athermal PNC films indicating the possible need for a new theoretical model.
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Affiliation(s)
- Aparna Swain
- Department of Physics, Indian Institute of Science, Bangalore 560012, India.
| | - Nafisa Begam
- Department of Physics, Indian Institute of Science, Bangalore 560012, India.
| | | | - M S Bobji
- Indian Institute of Science, Department of Mechanical Engineering, Indian Institute of Science, Bangalore, 560012, India
| | - J K Basu
- Department of Physics, Indian Institute of Science, Bangalore 560012, India.
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Hoang QV, Rohrbach D, McFadden SA, Mamou J. Regional changes in the elastic properties of myopic Guinea pig sclera. Exp Eye Res 2019; 186:107739. [PMID: 31330141 PMCID: PMC6712578 DOI: 10.1016/j.exer.2019.107739] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Revised: 07/11/2019] [Accepted: 07/18/2019] [Indexed: 11/17/2022]
Abstract
Biomechanical changes in the sclera likely underlie the excessive eye elongation of axial myopia. We studied the biomechanical characteristics of myopic sclera at the microscopic level using scanning acoustic microscopy (SAM) with 7-μm in-plane resolution. Guinea pigs underwent form-deprivation (FD) in one eye from 4 to 12 days of age to induce myopia, and 12-μm-thick scleral cryosections were scanned using a custom-made SAM. Two-dimensional maps of the bulk modulus (K) and mass density (ρ) were derived from the SAM data using a frequency-domain approach. We assessed the effect on K and ρ exerted by: 1) level of induced myopia, 2) region (superior, inferior, nasal or temporal) and 3) eccentricity from the nerve using univariate and multivariate regression analyses. Induced myopia ranged between -3D and -9.3D (Mean intraocular difference of -6.2 ± 1.7D, N = 11). K decreased by 0.036 GPa for every 1.0 D increase in induced myopia across vertical sections (p < 0.001). Among induced myopia right eyes, K values in the inherently more myopic superior region were 0.088 GPa less than the inferior region (p = 0.002) and K in the proximal nasal region containing the central axis were 0.10 GPa less than temporal K (p = 0.036). K also increased 0.12 GPa for every 1 mm increase in superior vertical distance (p < 0.001), an effect that was blunted after 1 week of FD. Overall, trends for ρ were less apparent than for K. ρ values increased by 20.7 mg/cm3 for every 1.00 D increase in induced myopia across horizontal sections (p < 0.001), and were greatest in the region containing the central posterior pole. ρ values in the inherently more myopic superior region were 13.1 mg/cm3 greater than that found in inferior regions among control eyes (p = 0.002), and increased by 11.2 mg/cm3 for every 1 mm increase in vertical distance (p = 0.001). This peripheral increase in ρ was blunted after 1 week of FD. Scleral material properties vary depending on the location in the sclera and the level of induced myopia. Bulk modulus was most reduced in the most myopic regions (both induced myopia and inherent regional myopia), and suggests that FD causes microscopic local decreases in sclera stiffness, while scleral mass density was most increased in the most myopic regions.
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Affiliation(s)
- Quan V Hoang
- Department of Ophthalmology, Columbia University Medical Center, New York, NY, 10032, USA; Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Medical School, Singapore.
| | - Daniel Rohrbach
- Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, 10038, USA
| | - Sally A McFadden
- Vision Sciences, School of Psychology, Faculty of Science and Hunter Medical Research Institute, University of Newcastle, NSW, Australia
| | - Jonathan Mamou
- Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, 10038, USA
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Chang Z, Paoletti P, Hansen ML, Beck HC, Chen PY, Rasmussen LM, Akhtar R. AFM Characterization of the Internal Mammary Artery as a Novel Target for Arterial Stiffening. SCANNING 2018; 2018:6340425. [PMID: 30524642 PMCID: PMC6247466 DOI: 10.1155/2018/6340425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/06/2018] [Indexed: 05/05/2023]
Abstract
Using the atomic force microscopy- (AFM-) PeakForce quantitative nanomechanical mapping (QNM) technique, we have previously shown that the adventitia of the human internal mammary artery (IMA), tested under dehydrated conditions, is altered in patients with a high degree of arterial stiffening. In this study, we explored the nanoscale elastic modulus of the tunica media of the IMA in hydrated and dehydrated conditions from the patients with low and high arterial stiffening, as assessed in vivo by carotid-femoral pulse wave velocity (PWV). In both hydrated and dehydrated conditions, the medial layer was significantly stiffer in the high PWV group. The elastic modulus of the hydrated and dehydrated tunica media was significantly correlated with PWV. In the hydrated condition, the expression activity of certain small leucine-rich repeat proteoglycans (SLRPs), which are associated with arterial stiffening, were found to be negatively correlated to the medial elastic modulus. We also compared the data with our previous work on the IMA adventitia. We found that the hydrated media and dehydrated adventitia are both suitable for reflecting the development of arterial stiffening and SLRP expression. This comprehensive study of the nanomechanical properties integrated with the proteomic analysis in the IMAs demonstrates the possibility of linking structural properties and function in small biological samples with novel AFM methods. The IMA is a suitable target for predicting arterial stiffening.
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Affiliation(s)
- Zhuo Chang
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, L69 3GH, UK
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Paolo Paoletti
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, L69 3GH, UK
| | - Maria Lyck Hansen
- Department of Clinical Biochemistry and Pharmacology, Center for Individualized Medicine in Arterial Diseases, Odense University Hospital, University of Southern Denmark, Denmark
| | - Hans Christian Beck
- Department of Clinical Biochemistry and Pharmacology, Center for Individualized Medicine in Arterial Diseases, Odense University Hospital, University of Southern Denmark, Denmark
| | - Po-Yu Chen
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Lars Melholt Rasmussen
- Department of Clinical Biochemistry and Pharmacology, Center for Individualized Medicine in Arterial Diseases, Odense University Hospital, University of Southern Denmark, Denmark
| | - Riaz Akhtar
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, L69 3GH, UK
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Chlasta J, Milani P, Runel G, Duteyrat JL, Arias L, Lamiré LA, Boudaoud A, Grammont M. Variations in basement membrane mechanics are linked to epithelial morphogenesis. Development 2017; 144:4350-4362. [PMID: 29038305 DOI: 10.1242/dev.152652] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 10/05/2017] [Indexed: 12/12/2022]
Abstract
The regulation of morphogenesis by the basement membrane (BM) may rely on changes in its mechanical properties. To test this, we developed an atomic force microscopy-based method to measure BM mechanical stiffness during two key processes in Drosophila ovarian follicle development. First, follicle elongation depends on epithelial cells that collectively migrate, secreting BM fibrils perpendicularly to the anteroposterior axis. Our data show that BM stiffness increases during this migration and that fibril incorporation enhances BM stiffness. In addition, stiffness heterogeneity, due to oriented fibrils, is important for egg elongation. Second, epithelial cells change their shape from cuboidal to either squamous or columnar. We prove that BM softens around the squamous cells and that this softening depends on the TGFβ pathway. We also demonstrate that interactions between BM constituents are necessary for cell flattening. Altogether, these results show that BM mechanical properties are modified during development and that, in turn, such mechanical modifications influence both cell and tissue shapes.
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Affiliation(s)
- Julien Chlasta
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
| | - Pascale Milani
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
| | - Gaël Runel
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
| | - Jean-Luc Duteyrat
- Institut NeuroMyoGene, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, 16 rue R. Dubois, Villeurbanne Cedex F-69622, France
| | - Leticia Arias
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
| | - Laurie-Anne Lamiré
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
| | - Arezki Boudaoud
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342, Lyon, France
| | - Muriel Grammont
- Laboratoire de Biologie et de Modélisation de la Cellule, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, F-69342, Lyon, France
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Arthropod Corneal Nanocoatings: Diversity, Mechanisms, and Functions. BIOLOGICALLY-INSPIRED SYSTEMS 2017. [DOI: 10.1007/978-3-319-74144-4_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Chitosan nanofiber production from Drosophila by electrospinning. Int J Biol Macromol 2016; 92:49-55. [DOI: 10.1016/j.ijbiomac.2016.07.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 06/29/2016] [Accepted: 07/04/2016] [Indexed: 11/23/2022]
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