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Hui J, Nie X, Wei P, Deng J, Kang Y, Tang K, Han G, Wang L, Liu W, Han Q. 3D printed fibroblast-loaded hydrogel for scleral remodeling to prevent the progression of myopia. J Mater Chem B 2024; 12:2559-2570. [PMID: 38362614 DOI: 10.1039/d3tb02548a] [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: 02/17/2024]
Abstract
Pathologic myopia has seriously jeopardized the visual health of adolescents in the past decades. The progression of high myopia is associated with a decrease in collagen aggregation and thinning of the sclera, which ultimately leads to longer eye axis length and image formation in front of the retina. Herein, we report a fibroblast-loaded hydrogel as a posterior scleral reinforcement (PSR) surgery implant for the prevention of myopia progression. The fibroblast-loaded gelatin methacrylate (GelMA)-poly(ethylene glycol) diacrylate (PEGDA) hydrogel was prepared through bioprinting with digital light processing (DLP). The introduction of the PEGDA component endowed the GelMA-PEGDA hydrogel with a high compression modulus for PRS surgery. The encapsulated fibroblasts could consistently maintain a high survival rate during 7 days of in vitro incubation, and could normally secrete collagen type I. Eventually, both the hydrogel and fibroblast-loaded hydrogel demonstrated an effective shortening of the myopic eye axis length in a guinea pig model of visual deprivation over three weeks after implantation, and the sclera thickness of myopic guinea pigs became significantly thicker after 4 weeks, verifying the success of sclera remodeling and showing that myopic progression was effectively controlled. In particular, the fibroblast-loaded hydrogel demonstrated the best therapeutic effect through the synergistic effect of cell therapy and PSR surgery.
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Affiliation(s)
- Jingwen Hui
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
| | - Xiongfeng Nie
- School of Material Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300350, China
| | - Pinghui Wei
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
| | - Jie Deng
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- School of Medicine, Nankai University, Tianjin, China
| | - Yuanzhe Kang
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
| | - Kexin Tang
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
| | - Guoge Han
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
| | - Ling Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Tianjin 300071, China
| | - Wenguang Liu
- School of Material Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300350, China
| | - Quanhong Han
- Tianjin Eye Hospital, No. 4 Gansu Road, Heping District, Tianjin 300020, China.
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology Tianjin Medical University, Tianjin Medical University, Tianjin, China
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Guo H, Lan Y, Gao Z, Zhang C, Zhang L, Li X, Lin J, Elsheikh A, Chen W. Interaction between eye movements and adhesion of extraocular muscles. Acta Biomater 2024; 176:304-320. [PMID: 38296013 DOI: 10.1016/j.actbio.2024.01.028] [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: 08/07/2023] [Revised: 01/10/2024] [Accepted: 01/19/2024] [Indexed: 02/08/2024]
Abstract
The contact and pull-off tests and finite element simulations were used to study the extraocular muscle-sclera adhesion and its variation with eye movement in this research. The effect of the adhesion on the eye movements was also determined using equilibrium equations of eye motion. The contact and pull-off tests were performed using quasi-static and non-quasi-static unloading velocities. Finite element models were developed to simulate these tests in cases with high unloading velocity which could not be achieved experimentally. These velocities range from the eye's fixation to saccade movement. The tests confirmed that the pull-off force is related to the unloading velocity. As the unloading velocity increases, the pull-off force increases, with an insignificant increase at the high ocular saccade velocities. The adhesion moment between the extraocular muscles and the sclera exhibited the same trend, increasing with higher eye movement velocities and higher separation angles between the two interfaces. The adhesion moment ratio to the total moment was calculated by the traditional model and the active pulley model of eye movements to assess the effect of adhesion behavior on eye movements. At the high ocular saccade velocities (about 461 deg/s), the adhesion moment was found to be 0.53% and 0.50% of the total moment based on the traditional and active pulley models, respectively. The results suggest that the adhesion behavior between the extraocular muscles and the sclera has a negligible effect on eye movements. At the same time, this adhesion behavior can be ignored in eye modeling, which simplifies the model reasonably well. STATEMENT OF SIGNIFICANCE: 1. Adhesion behavior between the extraocular muscles and the sclera at different indenter unloading velocities determined by contact and pull-off tests. 2. A finite element model was developed to simulate the adhesive contact between the extraocular muscles and the sclera at different indenter unloading velocities. The bilinear cohesive zone model was used for adhesive interactions. 3. The elastic modulus and viscoelastic parameters of the extraocular muscle along the thickness direction were obtained by using compressive stress-relaxation tests. 4. The influence of the adhesion moment between the extraocular muscles and the sclera on eye movement was obtained according to the equation of oculomotor balance. The adhesion moment between the extraocular muscles and the sclera was found to increase with increased eye movement velocity and increased separation angle between the two interfaces.
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Affiliation(s)
- Hongmei Guo
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China; Third Hospital of Shanxi Medical University (Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital), Taiyuan 030032, China.
| | - Yunfei Lan
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Zhipeng Gao
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Chenxi Zhang
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Liping Zhang
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Xiaona Li
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Jianying Lin
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Weiyi Chen
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
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Rich W, Pan M, Liu J, Swindle-Reilly KE, Reilly MA. A method for generating zonular tension in the murine eye by embedding and compressing the globe in a hydrogel. Exp Eye Res 2024; 240:109809. [PMID: 38311284 DOI: 10.1016/j.exer.2024.109809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 12/08/2023] [Accepted: 01/25/2024] [Indexed: 02/10/2024]
Abstract
The ocular lens is the primary organ within the eye responsible for accommodation. During accommodation, the lens is subject to biomechanical forces. We previously demonstrated that stretching the porcine lens can increase lens epithelial cell proliferation. Although murine lenses are commonly employed in lens research, murine lens stretching has remained unexplored. Murine lens stretching thus represents a novel source of potential discovery in lens research. In the present study, we describe a method for stretching the murine lens by compressing the murine globe embedded in a hydrogel. We hypothesized that, as the eye is compressed along the optic axis, the lens would stretch through zonular tension due to the equatorial region of the eye bulging outward. Our results showed that this led to a compression-dependent increase in murine lens epithelial cell proliferation, suggesting that compression of the embedded murine globe is a viable technique for studying the mechanobiology of the lens epithelium.
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Affiliation(s)
- Wade Rich
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Manqi Pan
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Jun Liu
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA
| | - Katelyn E Swindle-Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA; William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, USA
| | - Matthew A Reilly
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA; Department of Ophthalmology and Visual Sciences, The Ohio State University, Columbus, OH, USA.
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Brown DM, Yu J, Kumar P, Paulus QM, Kowalski MA, Patel JM, Kane MA, Ethier CR, Pardue MT. Exogenous All-Trans Retinoic Acid Induces Myopia and Alters Scleral Biomechanics in Mice. Invest Ophthalmol Vis Sci 2023; 64:22. [PMID: 37219510 PMCID: PMC10210516 DOI: 10.1167/iovs.64.5.22] [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: 10/21/2022] [Accepted: 04/21/2023] [Indexed: 05/24/2023] Open
Abstract
Purpose Ocular all-trans retinoic acid (atRA) levels are influenced by visual cues, and exogenous atRA has been shown to increase eye size in chickens and guinea pigs. However, it is not clear whether atRA induces myopic axial elongation via scleral changes. Here, we test the hypothesis that exogenous atRA will induce myopia and alter scleral biomechanics in the mouse. Methods Male C57BL/6J mice were trained to voluntarily ingest atRA + vehicle (1% atRA in sugar, 25 mg/kg) (RA: n = 16 animals) or vehicle only (Ctrl: n = 14 animals). Refractive error (RE) and ocular biometry were measured at baseline and after 1 and 2 weeks of daily atRA treatment. Eyes were used in ex vivo assays to measure scleral biomechanics (unconfined compression: n = 18), total scleral sulfated glycosaminoglycan (sGAG) content (dimethylmethylene blue: n = 23), and specific sGAGs (immunohistochemistry: n = 18). Results Exogenous atRA caused myopic RE and larger vitreous chamber depth (VCD) to develop by 1 week (RE: -3.7 ± 2.2 diopters [D], P < 0.001; VCD: +20.7 ± 15.1 µm, P < 0.001), becoming more severe by 2 weeks (RE: -5.7 ± 2.2 D, P < 0.001; VCD: +32.3 ± 25.8 µm, P < 0.001). The anterior eye biometry was unaffected. While scleral sGAG content was not measurably affected, scleral biomechanics were significantly altered (tensile stiffness: -30% ± 19.5%, P < 0.001; permeability: +60% ± 95.3%, P < 0.001). Conclusions In mice, atRA treatment results in an axial myopia phenotype. Eyes developed myopic RE and larger VCD without the anterior eye being affected. The decrease in stiffness and increase in permeability of the sclera are consistent with the form-deprivation myopia phenotype.
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Affiliation(s)
- Dillon M. Brown
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
| | - Jianshi Yu
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - Praveen Kumar
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - Quinn M. Paulus
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
| | - Michael A. Kowalski
- Department of Orthopaedics, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Jay M. Patel
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
- Department of Orthopaedics, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Maureen A. Kane
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - C. Ross Ethier
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Machelle T. Pardue
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, United States
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Song D, Lim S, Park J, Demer JL. Linear viscoelasticity of human sclera and posterior ocular tissues during tensile creep. J Biomech 2023; 151:111530. [PMID: 36933327 DOI: 10.1016/j.jbiomech.2023.111530] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/21/2023] [Accepted: 03/02/2023] [Indexed: 03/13/2023]
Abstract
PURPOSE Despite presumed relevance to ocular diseases, the viscoelastic properties of the posterior human eye have not been evaluated in detail. We performed creep testing to characterize the viscoelastic properties of ocular regions, including the sclera, optic nerve (ON) and ON sheath. METHODS We tested 10 pairs of postmortem human eyes of average age 77 ± 17 years, consisting of 5 males and 5 females. Except for the ON that was tested in native shape, tissues were trimmed into rectangles. With physiologic temperature and constant wetting, tissues were rapidly loaded to tensile stress that was maintained by servo feedback as length was monitored for 1,500 sec. Relaxation modulus was computed using Prony series, and Deborah numbers estimated for times scales of physiological eye movements. RESULTS Correlation between creep rate and applied stress level was negligible for all tissues, permitting description as linear viscoelastic materials characterized by lumped parameter compliance equations for limiting behaviors. The ON was the most compliant, and anterior sclera least compliant, with similar intermediate values for posterior sclera and ON sheath. Sensitivity analysis demonstrated that linear behavior eventually become dominant after long time. For the range of typical pursuit tracking, all tissues exhibit Debora numbers less than 75, and should be regarded as viscoelastic. With a 6.7 Deborah number, this is especially so for the ON during pursuit and convergence. CONCLUSIONS Posterior ocular tissues exhibit creep consistent with linear viscoelasticity necessary for describing biomechanical behavior of the ON, its sheath, and sclera during physiological eye movements and eccentric ocular fixations. Running Head: Tensile Creep of Human Ocular Tissues.
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Affiliation(s)
- Dooseop Song
- Department of Mechanical Engineering, University of California, Los Angeles, United States; Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Seongjin Lim
- Department of Mechanical Engineering, University of California, Los Angeles, United States; Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Joseph Park
- Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Joseph L Demer
- Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States; Department of Bioengineering, University of California, Los Angeles, United States; Department of Neurology, University of California, Los Angeles, United States.
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Brown DM, Kowalski MA, Paulus QM, Yu J, Kumar P, Kane MA, Patel JM, Ethier CR, Pardue MT. Altered Structure and Function of Murine Sclera in Form-Deprivation Myopia. Invest Ophthalmol Vis Sci 2022; 63:13. [PMID: 36512347 PMCID: PMC9753793 DOI: 10.1167/iovs.63.13.13] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 11/15/2022] [Indexed: 12/15/2022] Open
Abstract
Purpose The sclera is believed to biomechanically influence eye size, facilitating the excessive axial elongation that occurs during myopigenesis. Here, we test the hypothesis that the sclera will be remodeled and exhibit altered biomechanics in the mouse model of form-deprivation (FD) myopia, accompanied by altered retinoid concentrations, a potential signaling molecule involved in the process. Methods Male C57 Bl/6J mice were subjected to unilateral FD (n = 44 eyes), leaving the contralateral eye untreated (contra; n = 44). Refractive error and ocular biometry were measured in vivo prior to and after 1 or 3 weeks of FD. Ex vivo measurements were made of scleral biomechanical properties (unconfined compression: n = 24), scleral sulfated glycosaminoglycan (sGAG) content (dimethylmethylene blue: n = 18, and immunohistochemistry: n = 22), and ocular all-trans retinoic acid (atRA) concentrations (retina and RPE + choroid + sclera, n = 24). Age-matched naïve controls were included for some outcomes (n = 32 eyes). Results Significant myopia developed after 1 (-2.4 ± 1.1 diopters [D], P < 0.001) and 3 weeks of FD (-4.1 ± 0.7 D, P = 0.025; mean ± standard deviation). Scleral tensile stiffness and permeability were significantly altered during myopigenesis (stiffness = -31.4 ± 12.7%, P < 0.001, and permeability = 224.4 ± 205.5%, P < 0.001). Total scleral sGAG content was not measurably altered; however, immunohistochemistry indicated a sustained decrease in chondroitin-4-sulfate and a slower decline in dermatan sulfate. The atRA increased in the retinas of eyes form-deprived for 1 week. Conclusions We report that biomechanics and GAG content of the mouse sclera are altered during myopigenesis. All scleral outcomes generally follow the trends found in other species and support a retina-to-sclera signaling cascade underlying mouse myopigenesis.
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Affiliation(s)
- Dillon M. Brown
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
| | - Michael A. Kowalski
- Department of Orthopedics, Emory University School of Medicine, Atlanta, Georgia, United States
| | - Quinn M. Paulus
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
| | - Jianshi Yu
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - Praveen Kumar
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - Maureen A. Kane
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, United States
| | - Jay M. Patel
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
- Department of Orthopedics, Emory University School of Medicine, Atlanta, Georgia, United States
| | - C. Ross Ethier
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
| | - Machelle T. Pardue
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, United States
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veterans Affairs Healthcare System, Atlanta, Georgia, United States
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Dwivedi KK, Lakhani P, Kumar S, Kumar N. Effect of collagen fibre orientation on the Poisson's ratio and stress relaxation of skin: an ex vivo and in vivo study. ROYAL SOCIETY OPEN SCIENCE 2022; 9:211301. [PMID: 35345435 PMCID: PMC8941416 DOI: 10.1098/rsos.211301] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
During surgical treatment skin undergoes extensive deformation, hence it must be able to withstand large mechanical stresses without damage. Therefore, understanding the mechanical properties of skin becomes important. A detailed investigation on the relationship between the three-dimensional deformation response of skin and its microstructure is conducted in the current study. This study also discloses the underlying science of skin viscoelasticity. Deformation response of skin is captured using digital image correlation, whereas micro-CT, scanning electron microscopy and atomic force microscopy are used for microstructure analysis. Skin shows a large lateral contraction and expansion (auxeticity) when stretched parallel and perpendicular to the skin tension lines, respectively. Large lateral contraction is a result of fluid exudation from the tissue, while large rotation of the stiff collagen fibres in the loading direction explains the skin auxeticity. During stress relaxation, lateral contraction and fluid effluxion from skin reveal that tissue volume loss is the intrinsic science of skin viscoelasticity. Furthermore, the results obtained from in vivo study on human skin show the relevance of the ex vivo study to physiological conditions and stretching of the skin during its treatments.
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Affiliation(s)
- Krashn Kumar Dwivedi
- Department of Biomedical Engineering, Indian Institute of Technology, Ropar, India
| | - Piyush Lakhani
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
| | - Sachin Kumar
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
| | - Navin Kumar
- Department of Biomedical Engineering, Indian Institute of Technology, Ropar, India
- Department of Mechanical Engineering, Indian Institute of Technology, Ropar, India
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Rohanifar M, Johnston BB, Davis AL, Guang Y, Nommensen K, Fitzpatrick JA, Pham CN, Setton LA. Hydraulic permeability and compressive properties of porcine and human synovium. Biophys J 2022; 121:575-581. [PMID: 35032457 PMCID: PMC8874024 DOI: 10.1016/j.bpj.2022.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/21/2021] [Accepted: 01/11/2022] [Indexed: 11/02/2022] Open
Abstract
The synovium is a multilayer connective tissue separating the intra-articular spaces of the diarthrodial joint from the extra-synovial vascular and lymphatic supply. Synovium regulates drug transport into and out of the joint, yet its material properties remain poorly characterized. Here, we measured the compressive properties (aggregate modulus, Young's modulus, and Poisson's ratio) and hydraulic permeability of synovium with a combined experimental-computational approach. A compressive aggregate modulus and Young's modulus for the solid phase of synovium were quantified from linear regression of the equilibrium confined and unconfined compressive stress upon strain, respectively (HA = 4.3 ± 2.0 kPa, Es = 2.1 ± 0.75, porcine; HA = 3.1 ± 2.0 kPa, Es = 2.8 ± 1.7, human). Poisson's ratio was estimated to be 0.39 and 0.40 for porcine and human tissue, respectively, from moduli values in a Monte Carlo simulation. To calculate hydraulic permeability, a biphasic finite element model's predictions were numerically matched to experimental data for the time-varying ramp and hold phase of a single increment of applied strain (k = 7.4 ± 4.1 × 10-15 m4/N.s, porcine; k = 7.4 ± 4.3 × 10-15 m4/N.s, human). We can use these newly measured properties to predict fluid flow gradients across the tissue in response to previously reported intra-articular pressures. These values for material constants are to our knowledge the first available measurements in synovium that are necessary to better understand drug transport in both healthy and pathological joints.
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Affiliation(s)
- Milad Rohanifar
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Benjamin B. Johnston
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Alexandra L. Davis
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Young Guang
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - Kayla Nommensen
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri
| | - James A.J. Fitzpatrick
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri,Department of Neuroscience and Cell Biology & Physiology, Washington University School of Medicine, St. Louis, Missouri
| | - Christine N. Pham
- Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, Missouri
| | - Lori A. Setton
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri,Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, Missouri,Corresponding author
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Safa BN, Read AT, Ethier CR. Assessment of the viscoelastic mechanical properties of the porcine optic nerve head using micromechanical testing and finite element modeling. Acta Biomater 2021; 134:379-387. [PMID: 34274532 PMCID: PMC8542610 DOI: 10.1016/j.actbio.2021.07.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 06/11/2021] [Accepted: 07/08/2021] [Indexed: 11/26/2022]
Abstract
Optic nerve head (ONH) biomechanics is centrally involved in the pathogenesis of glaucoma, a blinding ocular condition often characterized by elevation and fluctuation of the intraocular pressure and resulting loads on the ONH. Further, tissue viscoelasticity is expected to strongly influence the mechanical response of the ONH to mechanical loading, yet the viscoelastic mechanical properties of the ONH remain unknown. To determine these properties, we conducted micromechanical testing on porcine ONH tissue samples, coupled with finite element modeling based on a mixture model consisting of a biphasic material with a viscoelastic solid matrix. Our results provide a detailed description of the viscoelastic properties of the porcine ONH at each of its four anatomical quadrants (i.e., nasal, superior, temporal, and inferior). We showed that the ONH's viscoelastic mechanical response can be explained by a dual mechanism of fluid flow and solid matrix viscoelasticity, as is common in other soft tissues. We obtained porcine ONH properties as follows: matrix Young's modulus E=1.895[1.056,2.391] kPa (median [min., max.]), Poisson's ratio ν=0.142[0.060,0.312], kinetic time-constant τ=214[89,921] sec, and hydraulic permeability k=3.854×10-1[3.457×10-2,9.994×10-1] mm4/(N.sec). These values can be used to design and fabricate physiologically appropriate ex vivo test environments (e.g., 3D cell culture) to further understand glaucoma pathophysiology. STATEMENT OF SIGNIFICANCE: Optic nerve head (ONH) biomechanics is an important aspect of the pathogenesis of glaucoma, the leading cause of irreversible blindness. The ONH experiences time-varying loads, yet the viscoelastic behavior of this tissue has not been characterized. Here, we measure the time-dependent response of the ONH in porcine eyes and use mechanical modeling to provide time-dependent mechanical properties of the ONH. This information allows us to identify time-varying stimuli in vivo which have timescales matching the characteristic response times of the ONH, and can also be used to design and fabricate ex vivo 3D cultures to study glaucoma pathophysiology in a physiologically relevant environment, enabling the discovery of new generations of glaucoma medications focusing on neuroprotection.
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Affiliation(s)
- Babak N Safa
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
| | - A Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta GA, USA.
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Boazak EM, King R, Wang J, Chu CM, Toporek AM, Sherwood JM, Overby DR, Geisert EE, Ethier CR. Smarce1 and Tensin 4 Are Putative Modulators of Corneoscleral Stiffness. Front Bioeng Biotechnol 2021; 9:596154. [PMID: 33634081 PMCID: PMC7902041 DOI: 10.3389/fbioe.2021.596154] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 01/14/2021] [Indexed: 11/13/2022] Open
Abstract
The biomechanical properties of the cornea and sclera are important in the onset and progression of multiple ocular pathologies and vary substantially between individuals, yet the source of this variation remains unknown. Here we identify genes putatively regulating corneoscleral biomechanical tissue properties by conducting high-fidelity ocular compliance measurements across the BXD recombinant inbred mouse set and performing quantitative trait analysis. We find seven cis-eQTLs and non-synonymous SNPs associating with ocular compliance, and show by RT-qPCR and immunolabeling that only two of the candidate genes, Smarce1 and Tns4, showed significant expression in corneal and scleral tissues. Both have mechanistic potential to influence the development and/or regulation of tissue material properties. This work motivates further study of Smarce1 and Tns4 for their role(s) in ocular pathology involving the corneoscleral envelope as well as the development of novel mouse models of ocular pathophysiology, such as myopia and glaucoma.
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Affiliation(s)
- Elizabeth M Boazak
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
| | - Rebecca King
- Department of Ophthalmology, Emory University, Atlanta, GA, United States
| | - Jiaxing Wang
- Department of Ophthalmology, Emory University, Atlanta, GA, United States
| | - Cassandra M Chu
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
| | - Aaron M Toporek
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, United States
| | - Joseph M Sherwood
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Darryl R Overby
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Eldon E Geisert
- Department of Ophthalmology, Emory University, Atlanta, GA, United States
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Emory University, Atlanta, GA, United States.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
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