1
|
Wong CA, Fraticelli Guzmán NS, Read AT, Hedberg-Buenz A, Anderson MG, Feola AJ, Sulchek T, Ethier CR. A method for analyzing AFM force mapping data obtained from soft tissue cryosections. J Biomech 2024; 168:112113. [PMID: 38648717 PMCID: PMC11128031 DOI: 10.1016/j.jbiomech.2024.112113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 02/23/2024] [Accepted: 04/17/2024] [Indexed: 04/25/2024]
Abstract
Atomic force microscopy (AFM) is a valuable tool for assessing mechanical properties of biological samples, but interpretations of measurements on whole tissues can be difficult due to the tissue's highly heterogeneous nature. To overcome such difficulties and obtain more robust estimates of tissue mechanical properties, we describe an AFM force mapping and data analysis pipeline to characterize the mechanical properties of cryosectioned soft tissues. We assessed this approach on mouse optic nerve head and rat trabecular meshwork, cornea, and sclera. Our data show that the use of repeated measurements, outlier exclusion, and log-normal data transformation increases confidence in AFM mechanical measurements, and we propose that this methodology can be broadly applied to measuring soft tissue properties from cryosections.
Collapse
Affiliation(s)
- Cydney A Wong
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | | | - A Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Adam Hedberg-Buenz
- Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA
| | - Michael G Anderson
- Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA
| | - Andrew J Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Department of Ophthalmology, Emory University, Atlanta, GA; Center for Visual & Neurocognitive Rehabilitation, Atlanta Veterans Affairs Medical Center, Decatur, GA
| | - Todd Sulchek
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA; Department of Ophthalmology, Emory University, Atlanta, GA.
| |
Collapse
|
2
|
Ji F, Islam MR, Wang B, Hua Y, Sigal IA. Lamina Cribrosa Insertions Into the Sclera Are Sparser, Narrower, and More Slanted in the Anterior Lamina. Invest Ophthalmol Vis Sci 2024; 65:35. [PMID: 38648038 PMCID: PMC11044832 DOI: 10.1167/iovs.65.4.35] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 04/03/2024] [Indexed: 04/25/2024] Open
Abstract
Purpose The lamina cribrosa (LC) depends on the sclera for support. The support must be provided through the LC insertions. Although a continuous insertion over the whole LC periphery is often assumed, LC insertions are actually discrete locations where LC collagenous beams meet the sclera. We hypothesized that LC insertions vary in number, size, and shape by quadrant and depth. Methods Coronal cryosections through the full LCs from six healthy monkey eyes were imaged using instant polarized light microscopy. The images were registered into a stack, on which we manually marked LC insertion outlines, nothing their position in-depth and quadrant (inferior, superior, nasal, or temporal). From the marks, we determined the insertion number, width, angle to the canal wall (90 degrees = perpendicular), and insertion ratio (fraction of LC periphery represented by insertions). Using linear mixed effect models, we determined if the insertion characteristics were associated with depth or quadrant. Results Insertions in the anterior LC were sparser, narrower, and more slanted than those in deeper LC (P values < 0.001). There were more insertions spanning a larger ratio of the canal wall in the middle LC than in the anterior and posterior (P values < 0.001). In the nasal quadrant, the insertion angles were significantly smaller (P < 0.001). Conclusions LC insertions vary substantially and significantly over the canal. The sparser, narrower, and more slanted insertions of the anterior-most LC may not provide the robust support afforded by insertions of the middle and posterior LC. These variations may contribute to the progressive deepening of the LC and regional susceptibility to glaucoma.
Collapse
Affiliation(s)
- Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Mohammad R. Islam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Mechanical Engineering, University of Texas Rio Grande Valley, Edinburg, Texas, United States
| | - Bingrui Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Biomedical Engineering, University of Mississippi, University, Mississippi, United States
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
3
|
Islam MR, Ji F, Bansal M, Hua Y, Sigal IA. Fibrous finite element modeling of the optic nerve head region. Acta Biomater 2024; 175:123-137. [PMID: 38147935 DOI: 10.1016/j.actbio.2023.12.034] [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: 05/17/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 12/28/2023]
Abstract
The optic nerve head (ONH) region at the posterior pole of the eye is supported by a fibrous structure of collagen fiber bundles. Discerning how the fibrous structure determines the region biomechanics is crucial to understand normal physiology, and the roles of biomechanics on vision loss. The fiber bundles within the ONH structure exhibit complex three-dimensional (3D) organization and continuity across the various tissue components. Computational models of the ONH, however, usually represent collagen fibers in a homogenized fashion without accounting for their continuity across tissues, fibers interacting with each other and other fiber-specific effects in a fibrous structure. We present a fibrous finite element (FFE) model of the ONH that incorporates discrete collagen fiber bundles and their histology-based 3D organization to study ONH biomechanics as a fibrous structure. The FFE model was constructed using polarized light microscopy data of porcine ONH cryosections, representing individual fiber bundles in the sclera, dura and pia maters with beam elements and canal tissues as continuum structures. The FFE model mimics the histological in-plane orientation and width distributions of collagen bundles as well as their continuity across different tissues. Modeling the fiber bundles as linear materials, the FFE model predicts the nonlinear ONH response observed in an inflation experiment from the literature. The model also captures important microstructural mechanisms including fiber interactions and long-range strain transmission among bundles that have not been considered before. The FFE model presented here advances our understanding of the role of fibrous collagen structure in the ONH biomechanics. STATEMENT OF SIGNIFICANCE: The microstructure and mechanics of the optic nerve head (ONH) are central to ocular physiology. Histologically, the ONH region exhibits a complex continuous fibrous structure of collagen bundles. Understanding the role of the fibrous collagen structure on ONH biomechanics requires high-fidelity computational models previously unavailable. We present a computational model of the ONH that incorporates histology-based fibrous collagen structure derived from polarized light microscopy images. The model predictions agree with experiments in the literature, and provide insight into important microstructural mechanisms of fibrous tissue biomechanics, such as long-range strain transmission along fiber bundles. Our model can be used to study the microstructural basis of biomechanical damage and the effects of collagen remodeling in glaucoma.
Collapse
Affiliation(s)
- Mohammad R Islam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Mechanical Engineering, University of Texas Rio Grande Valley, Edinburg TX, USA
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA
| | - Manik Bansal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Biomedical Engineering, University of Mississippi, MS, USA
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA.
| |
Collapse
|
4
|
Ji F, Quinn M, Hua Y, Lee PY, Sigal IA. 2D or not 2D? Mapping the in-depth inclination of the collagen fibers of the corneoscleral shell. Exp Eye Res 2023; 237:109701. [PMID: 37898229 PMCID: PMC10872428 DOI: 10.1016/j.exer.2023.109701] [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: 06/26/2023] [Revised: 10/16/2023] [Accepted: 10/26/2023] [Indexed: 10/30/2023]
Abstract
The collagen fibers of the corneoscleral shell play a central role in the eye mechanical behavior. Although it is well-known that these fibers form a complex three-dimensional interwoven structure, biomechanical and microstructural studies often assume that the fibers are aligned in-plane with the tissues. This is convenient as it removes the out-of-plane components and allows focusing on the 2D maps of in-plane fiber organization that are often quite complex. The simplification, however, risks missing potentially important aspects of the tissue architecture and mechanics. In the cornea, for instance, fibers with high in-depth inclination have been shown to be mechanically important. Outside the cornea, the in-depth fiber orientations have not been characterized, preventing a deeper understanding of their potential roles. Our goal was to characterize in-depth collagen fiber organization over the whole corneoscleral shell. Seven sheep whole-globe axial sections from eyes fixed at an IOP of 50 mmHg were imaged using polarized light microscopy to measure collagen fiber orientations and density. In-depth fiber orientation distributions and anisotropy (degree of fiber alignment) accounting for fiber density were quantified over the whole sclera and in 15 regions: central cornea, peripheral cornea, limbus, anterior equator, equator, posterior equator, posterior sclera and peripapillary sclera on both nasal and temporal sides. Orientation distributions were fitted using a combination of a uniform distribution and a sum of π-periodic von Mises distributions, each with three parameters: primary orientation μ, fiber concentration factor k, and weighting factor a. To study the features of fibers that are not in-plane, i.e., fiber inclination, we quantified the percentage of inclined fibers and the range of inclination angles (half width at half maximum of inclination angle distribution). Our measurements showed that the fibers were not uniformly in-plane but exhibited instead a wide range of in-depth orientations, with fibers significantly more aligned in-plane in the anterior parts of the globe. We found that fitting the orientation distributions required between one and three π-periodic von Mises distributions with different primary orientations and fiber concentration factors. Regions of the posterior globe, particularly on the temporal side, had a larger percentage of inclined fibers and a larger range of inclination angles than anterior and equatorial regions. Variations of orientation distributions and anisotropies may imply varying out-of-plane tissue mechanical properties around the eye globe. Out-of-plane fibers could indicate fiber interweaving, not necessarily long, inclined fibers. Effects of small-scale fiber undulations, or crimp, were minimized by using tissues from eyes at high IOPs. These fiber features also play a role in tissue stiffness and stability and are therefore also important experimental information.
Collapse
Affiliation(s)
- Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Marissa Quinn
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering and Department of Mechanical Engineering, University of Mississippi, University, MS, USA
| | - Po-Yi Lee
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
| |
Collapse
|
5
|
Keiler J, Stahnke T, Guthoff RF, Wree A, Runge J. Ex Vivo Micro-CT in Ophthalmology: Preparation and Contrasting for Non-invasive 3D-Visualisation. Klin Monbl Augenheilkd 2023; 240:1359-1368. [PMID: 38092003 DOI: 10.1055/a-2111-8415] [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: 12/18/2023]
Abstract
X-ray-based micro-computed tomography (micro-CT) is a largely non-destructive imaging method for the visualisation and analysis of internal structures in the ex vivo eye and affords high resolution. In contrast to other high-resolution imaging methods, micro-CT enables spatial recording of larger and more complex tissue structures, such as the anterior chamber of the eye. Special contrasting methods help to enhance the absorption properties of soft tissue, that is otherwise only weakly radiopaque. Critical point drying (CPD), as primarily used in scanning electron microscopy, offers an additional tool for improving differential contrast properties in soft tissue. In the visualisation of intraosseous soft tissue, such as the efferent lacrimal ducts, sample treatment by decalcification with ethylenediaminetetraacetic acid and subsequent CPD provides good results for micro-CT. Micro-CT can be used for a wide range of questions in 1. basic research, 2. application-related studies in ophthalmology (e.g. evaluation of the preclinical application of microstents for glaucoma treatment or analysis of the positioning of intraocular lenses) but also 3. as a supplement to ophthalmological histopathology.
Collapse
Affiliation(s)
- Jonas Keiler
- Institut für Anatomie, Universitätsmedizin Rostock, Deutschland
| | - Thomas Stahnke
- Klinik und Poliklinik für Augenheilkunde, Universitätsmedizin Rostock, Deutschland
- Institut für ImplantatTechnologie und Biomaterialien e. V., Warnemünde, Deutschland
| | - Rudolf F Guthoff
- Klinik und Poliklinik für Augenheilkunde, Universitätsmedizin Rostock, Deutschland
| | - Andreas Wree
- Institut für Anatomie, Universitätsmedizin Rostock, Deutschland
| | - Jens Runge
- Institut für Anatomie, Universitätsmedizin Rostock, Deutschland
- Klinik und Poliklinik für Augenheilkunde, Universitätsmedizin Rostock, Deutschland
| |
Collapse
|
6
|
Wong CA, Fraticelli Guzmán NS, Read AT, Hedberg-Buenz A, Anderson MG, Feola AJ, Sulchek T, Ethier CR. A Method for Analyzing AFM Force Mapping Data Obtained from Soft Tissue Cryosections. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566263. [PMID: 38014311 PMCID: PMC10680563 DOI: 10.1101/2023.11.08.566263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Atomic force microscopy (AFM) is a valuable tool for assessing mechanical properties of biological samples, but interpretations of measurements on whole tissues can be difficult due to the tissue's highly heterogeneous nature. To overcome such difficulties and obtain more robust estimates of tissue mechanical properties, we describe an AFM force mapping and data analysis pipeline to characterize the mechanical properties of cryosectioned soft tissues. We assessed this approach on mouse optic nerve head and rat trabecular meshwork, cornea, and sclera. Our data show that the use of repeated measurements, outlier exclusion, and log-normal data transformation increases confidence in AFM mechanical measurements, and we propose that this methodology can be broadly applied to measuring soft tissue properties from cryosections.
Collapse
Affiliation(s)
- Cydney A Wong
- 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
| | - Adam Hedberg-Buenz
- Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA
| | - Michael G Anderson
- Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA
| | - Andrew J Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA
- Center for Visual & Neurocognitive Rehabilitation, Atlanta VA Medical Center, Atlanta GA
| | - Todd Sulchek
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA, USA
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, GA, USA
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA
| |
Collapse
|
7
|
Foong TY, Hua Y, Amini R, Sigal IA. Who bears the load? IOP-induced collagen fiber recruitment over the corneoscleral shell. Exp Eye Res 2023; 230:109446. [PMID: 36935071 PMCID: PMC10133210 DOI: 10.1016/j.exer.2023.109446] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 02/25/2023] [Accepted: 03/16/2023] [Indexed: 03/19/2023]
Abstract
Collagen is the main load-bearing component of cornea and sclera. When stretched, both of these tissues exhibit a behavior known as collagen fiber recruitment. In recruitment, as the tissues stretch the constitutive collagen fibers lose their natural waviness, progressively straightening. Recruited, straight, fibers bear substantially more mechanical load than non-recruited, wavy, fibers. As such, the process of recruitment underlies the well-established nonlinear macroscopic behavior of the corneoscleral shell. Recruitment has an interesting implication: when recruitment is incomplete, only a fraction of the collagen fibers is actually contributing to bear the loads, with the rest remaining "in reserve". In other words, at a given intraocular pressure (IOP), it is possible that not all the collagen fibers of the cornea and sclera are actually contributing to bear the loads. To the best of our knowledge, the fraction of corneoscleral shell fibers recruited and contributing to bear the load of IOP has not been reported. Our goal was to obtain regionally-resolved estimates of the fraction of corneoscleral collagen fibers recruited and in reserve. We developed a fiber-based microstructural constitutive model that could account for collagen fiber undulations or crimp via their tortuosity. We used experimentally-measured collagen fiber crimp tortuosity distributions in human eyes to derive region-specific nonlinear hyperelastic mechanical properties. We then built a three-dimensional axisymmetric model of the globe, assigning region-specific mechanical properties and regional anisotropy. The model was used to simulate the IOP-induced shell deformation. The model-predicted tissue stretch was then used to quantify collagen recruitment within each shell region. The calculations showed that, at low IOPs, collagen fibers in the posterior equator were recruited the fastest, such that at a physiologic IOP of 15 mmHg, over 90% of fibers were recruited, compared with only a third in the cornea and the peripapillary sclera. The differences in recruitment between regions, in turn, mean that at a physiologic IOP the posterior equator had a fiber reserve of only 10%, whereas the cornea and peripapillary sclera had two thirds. At an elevated IOP of 50 mmHg, collagen fibers in the limbus and the anterior/posterior equator were almost fully recruited, compared with 90% in the cornea and the posterior sclera, and 70% in the peripapillary sclera and the equator. That even at such an elevated IOP not all the fibers were recruited suggests that there are likely other conditions that challenge the corneoscleral tissues even more than IOP. The fraction of fibers recruited may have other potential implications. For example, fibers that are not bearing loads may be more susceptible to enzymatic digestion or remodeling. Similarly, it may be possible to control tissue stiffness through the fraction of recruited fibers without the need to add or remove collagen.
Collapse
Affiliation(s)
- Tian Yong Foong
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Biomedical Engineering, University of Mississippi, MS, United States; Department of Mechanical Engineering, University of Mississippi, MS, United States
| | - Rouzbeh Amini
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, United States; Department of Bioengineering, Northeastern University, Boston, MA, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States; McGowan Institute for Regenerative Medicine, University of Pittsburgh Medical Center and University of Pittsburgh, Pittsburgh, PA, United States.
| |
Collapse
|
8
|
Zhu Z, Waxman S, Wang B, Wallace J, Schmitt SE, Tyler-Kabara E, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. In vivo Modulation of Intraocular and Intracranial Pressures Causes Nonlinear and Non-monotonic Deformations of the Lamina Cribrosa and Scleral Canal. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.29.526113. [PMID: 36778255 PMCID: PMC9915473 DOI: 10.1101/2023.01.29.526113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Purpose To evaluate changes in monkey optic nerve head (ONH) morphology under acutely controlled intraocular pressure (IOP) and intracranial pressure (ICP). Methods Seven ONHs from six monkeys were imaged via optical coherence tomography while IOP and ICP were maintained at one of 16 conditions. These conditions were defined by 4 levels for each pressure: low, baseline, high and very high. Images were processed to determine scleral canal area, aspect ratio, and planarity and anterior lamina cribrosa (ALC) shape index and curvature. Linear mixed effect models were utilized to investigate the effects of IOP, ICP and their interactions on ONH morphological features. The IOP-ICP interaction model was compared with one based on translaminar pressure difference (TLPD). Results We observed complex, eye-specific, non-linear patterns of ONH morphological changes with changes in IOP and ICP. For all ONH morphological features, linear mixed effects models demonstrated significant interactions between IOP and ICP that were unaccounted for by TLPD. Interactions indicate that the effects of IOP and ICP depend on the other pressure. The IOP-ICP interaction model was a higher quality predictor of ONH features than a TLPD model. Conclusions In vivo modulation of IOP and ICP causes nonlinear and non-monotonic changes in monkey ONH morphology that depend on both pressures and is not accounted for by a simplistic TLPD. These results support and extend prior findings. Translational Relevance A better understanding of ICP's influence on the effects of IOP can help inform the highly variable presentations of glaucoma and effective treatment strategies.
Collapse
Affiliation(s)
- Ziyi Zhu
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha E. Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Elizabeth Tyler-Kabara
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Neurosurgery, University of Texas-Austin, Austin, TX, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, OR, USA
- Department of Medical Informatics and Clinical Epidemiology (DMICE), Oregon Health & Science University, Portland, OR, USA
| | - Joel S. Schuman
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Matthew A. Smith
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Ian A. Sigal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| |
Collapse
|
9
|
Wei J, Hua Y, Yang B, Wang B, Schmitt SE, Wang B, Lucy KA, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. Comparing Acute IOP-Induced Lamina Cribrosa Deformations Premortem and Postmortem. Transl Vis Sci Technol 2022; 11:1. [DOI: 10.1167/tvst.11.12.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Affiliation(s)
- Junchao Wei
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Engineering, Duquesne University, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Samantha E. Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Bingrui Wang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Katie A. Lucy
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
- Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR, USA
- Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, OR, USA
| | - Joel S. Schuman
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
- Department of Biomedical Engineering and Electrical and Computer Engineering, New York University Tandon School of Engineering, Brooklyn, NY, USA
- Neuroscience Institute, NYU Langone Health, New York, NY, USA
| | - Matthew A. Smith
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU Langone Health, NYU Grossman School of Medicine, New York, NY, USA
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| |
Collapse
|
10
|
Panda-Jonas S, Auffarth GU, Jonas JB, Jonas RA. Elongation of the Retina and Ciliary Body in Dependence of the Sagittal Eye Diameter. Invest Ophthalmol Vis Sci 2022; 63:18. [PMID: 36169948 PMCID: PMC9526358 DOI: 10.1167/iovs.63.10.18] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To examine the elongation of the retina and ciliary body in relation to myopic axial elongation. Methods Using light microscopy, we histomorphometrically measured in enucleated human globes the length of the retina from the ora serrata to the optic disc borders. The total retinal length was the mean of the retinal length measurements obtained on both sides of the optic disc. We additionally determined the length of the ciliary body between the ora serrata and the scleral spur. Results The study included 174 eyes (mean age, 61.7 ± 14.8 years; range, 24-89 years) with a mean sagittal eye diameter of 25.9 ± 3.2 mm (range, 21.0-37.0 mm). Retinal length (beta, 0.81; nonstandardized regression coefficient B, 0.73; 95% confidence interval (CI), 0.65-0.81; P < 0.001) and ciliary body length elongated (beta, 0.49; nonstandardized regression coefficient B, 0.16; 95% CI, 0.12-0.20; P < 0.001) with a longer sagittal eye diameter. Retinal length and ciliary body length were associated with each other (beta, 0.34; nonstandardized regression coefficient B, 0.12; 95% CI, 0.07-0.17). Conclusions The retina elongates by 0.73 mm (95% CI, 0.65-0.81) and the ciliary body by 0.16 mm (95% CI, 0.12-0.20) for each millimeter of axial elongation. With the inner limiting membrane and retinal nerve fibers forming the only structures connecting the deeper retinal layers with the optic disc, retinal elongation may be associated with a stretching of the retinal nerve fibers, potentially leading to optic nerve damage in highly myopic eyes, and with an increased strain within the inner limiting membrane, potentially leading to an intraretinal elevation at the posterior pole with the sequel of a myopic maculoschisis.
Collapse
Affiliation(s)
- Songhomitra Panda-Jonas
- Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.,Privatpraxis Prof Jonas und Dr Panda-Jonas, Heidelberg, Germany
| | - Gerd U Auffarth
- Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany
| | - Jost B Jonas
- Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany.,Department of Ophthalmology, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany.,Institute of Molecular and Clinical Ophthalmology Basel, Switzerland
| | - Rahul A Jonas
- Department of Ophthalmology, University Hospital of Cologne, Cologne, Germany
| |
Collapse
|
11
|
Hua Y, Lu Y, Walker J, Lee PY, Tian Q, McDonald H, Pallares P, Ji F, Brazile BL, Yang B, Voorhees AP, Sigal IA. Eye-specific 3D modeling of factors influencing oxygen concentration in the lamina cribrosa. Exp Eye Res 2022; 220:109105. [PMID: 35568202 PMCID: PMC11007759 DOI: 10.1016/j.exer.2022.109105] [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: 12/21/2021] [Revised: 04/06/2022] [Accepted: 04/28/2022] [Indexed: 11/29/2022]
Abstract
Our goal was to identify the factors with the strongest influence on the minimum lamina cribrosa (LC) oxygen concentration as potentially indicative of conditions increasing hypoxia risk. Because direct measurement of LC hemodynamics and oxygenation is not yet possible, we developed 3D eye-specific LC vasculature models. The vasculature of a normal monkey eye was perfusion-labeled post-mortem. Serial cryosections through the optic nerve head were imaged using fluorescence and polarized light microscopy to visualize the vasculature and collagen, respectively. The vasculature within a 450 μm-thick region containing the LC - identified from the collagen, was segmented, skeletonized, and meshed for simulations. Using Monte Carlo sampling, 200 vascular network models were generated with varying vessel diameter, neural tissue oxygen consumption rate, inflow hematocrit, and blood pressures (arteriole, venule, anterior boundary, and posterior boundary). Factors were varied over ranges of baseline ±20% with uniform probability. For each model we first obtained the blood flow, and from this the neural tissue oxygen concentration. ANOVA was used to identify the factors with the strongest influence on the minimum (10th percentile) oxygen concentration in the LC. The three most influential factors were, in ranked order, vessel diameter, neural tissue oxygen consumption rate, and arteriole pressure. There was a strong interaction between vessel diameter and arteriole pressure whereby the impact of one factor was larger when the other factor was small. Our results show that, for the eye analyzed, conditions that reduce vessel diameter, such as vessel compression due to elevated intraocular pressure or gaze-induced tissue deformation, may particularly contribute to decreased LC oxygen concentration. More eyes must be analyzed before generalizing.
Collapse
Affiliation(s)
- Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Yuankai Lu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Jason Walker
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Po-Yi Lee
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Qi Tian
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Haiden McDonald
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Pedro Pallares
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Engineering, Rangos School of Health Sciences, Duquesne University, Pittsburgh, PA, United States
| | - Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
| |
Collapse
|
12
|
Wu X, Deng C, Su Y, Zhang C, Chen M, Tian K, Wu H, Xu S. The effect of prolonged formalin fixation on the expression of proteins in human brain tissues. Acta Histochem 2022; 124:151879. [PMID: 35358895 DOI: 10.1016/j.acthis.2022.151879] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/04/2022] [Accepted: 03/14/2022] [Indexed: 11/24/2022]
Abstract
Formalin-fixed, paraffin-embedded (FFPE) tissues have been widely used in researches. Proteins and nucleic acids in prolonged FFPE tissues display different degrees of degradation. We investigated the effect of prolonged formalin fixation on protein expression in human brain tissues. Twenty-eight middle prefrontal front cortex tissue blocks from human brains prefixed in formalin were obtained from a brain bank. The tissue blocks were divided into two groups, the control group and the prolonged fixation group. Quantitative immunocytochemistry was used to analyse the biological markers of Fox-3, Rbfox3 (NeuN), glial fibrillary acidic protein (GFAP), ionized calcium binding adapter molecule-1 (IBA-1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Nissl staining showed that positive signaling of Nissl body was significantly decreased by 16.6% in the prolonged fixation group. In addition, the staining intensity of Nissl body was negatively correlated with fixation time. The level of NeuN immunoreactivity (ir) was significantly reduced by 19.31% in the prolonged fixation group. Moreover, there was a significant negative correlation between NeuN-ir and fixation time. There were no significant changes in GFAP-ir, IBA-1-ir and GAPDH-ir between control group and the prolonged fixation group. Prolonged formalin-fixed tissues showed time- and molecule-dependent protein changes, which may be potential confounders in the clinic and researches. Our study suggested short formalin fixation time is recommended when using PPFE brain tissues.
Collapse
|
13
|
Zouache MA. Variability in Retinal Neuron Populations and Associated Variations in Mass Transport Systems of the Retina in Health and Aging. Front Aging Neurosci 2022; 14:778404. [PMID: 35283756 PMCID: PMC8914054 DOI: 10.3389/fnagi.2022.778404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 01/13/2022] [Indexed: 11/17/2022] Open
Abstract
Aging is associated with a broad range of visual impairments that can have dramatic consequences on the quality of life of those impacted. These changes are driven by a complex series of alterations affecting interactions between multiple cellular and extracellular elements. The resilience of many of these interactions may be key to minimal loss of visual function in aging; yet many of them remain poorly understood. In this review, we focus on the relation between retinal neurons and their respective mass transport systems. These metabolite delivery systems include the retinal vasculature, which lies within the inner portion of the retina, and the choroidal vasculature located externally to the retinal tissue. A framework for investigation is proposed and applied to identify the structures and processes determining retinal mass transport at the cellular and tissue levels. Spatial variability in the structure of the retina and changes observed in aging are then harnessed to explore the relation between variations in neuron populations and those seen among retinal metabolite delivery systems. Existing data demonstrate that the relation between inner retinal neurons and their mass transport systems is different in nature from that observed between the outer retina and choroid. The most prominent structural changes observed across the eye and in aging are seen in Bruch’s membrane, which forms a selective barrier to mass transfers at the interface between the choroidal vasculature and the outer retina.
Collapse
|
14
|
Bowen AJ, San‐Marina S, Hunter D, Voss S, Bartemes K, Macura S, Meloche R, Spragg AM, Lohse C, Oldenburg MS, Ekbom DC. MRI
imaging versus histologic volumetric estimation of residual injection laryngoplasty material. Laryngoscope Investig Otolaryngol 2022; 7:454-459. [PMID: 35434315 PMCID: PMC9008163 DOI: 10.1002/lio2.744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 01/11/2022] [Indexed: 12/03/2022] Open
Abstract
Objectives To examine the degree of agreement between MRI and histologically generated volumetric measurements of residual injection laryngoplasty material. Methods Following left recurrent laryngeal nerve transection, rabbit vocal cords were injected with jellyfish collagen, Cymetra®, or Restylane®. Laryngeal tissue was harvested 4 or 12 weeks post injection followed by MRI imaging and histologic cross‐sectioning. Two raters estimated the volume of remaining injection material in specimens within MRI and histologic axial cross sections. Wilcoxon signed rank tests were employed to detect gross differences between inter‐rater measurements and between imaging modalities across time. Agreement between rater measurements and imaging (histology and MRI) was assessed using intra‐class correlation coefficients. Results Data was available from 16 rabbits sacrificed at 4 weeks (n = 8) and 12 weeks (n = 8). Inter‐rater testing of MRI imaging revealed no significant differences (p > .05) between rater measurements across time points, and excellent agreement (0.93; 95% confidence interval 0.80–0.98) while histologically estimated volumes demonstrated a significant difference at 4 weeks (p < .05) and overall good agreement (0.89; 95% confidence interval 0.59–0.97). Comparison of MRI and histologically estimated volume measurements revealed significant differences at the 4‐week time point (p < .05) but not at 12 weeks (p > .05). Overall, there is only moderate agreement between MRI and histology estimates (0.72; 95% confidence interval 0.22–0.90). Conclusions MRI imaging demonstrates good reliability and similar estimates of volume to histologically estimated measurements of residual injection laryngoplasty material at time points clinically relevant for future injection laryngoplasty experiments. Level of Evidence NA.
Collapse
Affiliation(s)
- Andrew Jay Bowen
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| | - Serban San‐Marina
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| | - Danielle Hunter
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| | - Stephen Voss
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| | - Kathleen Bartemes
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| | - Slobodan Macura
- Department of Biochemistry and Molecular Biology & Metabolomics Core Mayo Clinic Rochester Minnesota USA
| | - Ryan Meloche
- Department of Biochemistry and Molecular Biology & Metabolomics Core Mayo Clinic Rochester Minnesota USA
| | | | - Christine Lohse
- Department of Health Sciences Research Mayo Clinic Rochester Minnesota USA
| | | | - Dale C. Ekbom
- Department of Otorhinolaryngology Mayo Clinic Rochester Minnesota USA
| |
Collapse
|
15
|
Waxman S, Brazile BL, Yang B, Lee PY, Hua Y, Gogola AL, Lam P, Voorhees AP, Rizzo JF, Jakobs TC, Sigal IA. Lamina cribrosa vessel and collagen beam networks are distinct. Exp Eye Res 2022; 215:108916. [PMID: 34973204 PMCID: PMC8923914 DOI: 10.1016/j.exer.2021.108916] [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: 10/04/2021] [Revised: 11/29/2021] [Accepted: 12/23/2021] [Indexed: 02/03/2023]
Abstract
Our goal was to analyze the spatial interrelation between vascular and collagen networks in the lamina cribrosa (LC). Specifically, we quantified the percentages of collagen beams with/without vessels and of vessels inside/outside of collagen beams. To do this, the vasculature of six normal monkey eyes was labeled by perfusion post-mortem. After enucleation, coronal cryosections through the LC were imaged using fluorescence and polarized light microscopy to visualize the blood vessels and collagen beams, respectively. The images were registered to form 3D volumes. Beams and vessels were segmented, and their spatial interrelationship was quantified in 3D. We found that 22% of the beams contained a vessel (range 14%-32%), and 21% of vessels were outside beams (13%-36%). Stated differently, 78% of beams did not contain a vessel (68%-86%), and 79% of vessels were inside a beam (64%-87%). Individual monkeys differed significantly in the fraction of vessels outside beams (p < 0.01 by linear mixed effect analysis), but not in the fraction of beams with vessels (p > 0.05). There were no significant differences between contralateral eyes in the percent of beams with vessels and of vessels outside beams (p > 0.05). Our results show that the vascular and collagenous networks of the LC in monkey are clearly distinct, and the historical notions that each LC beam contains a vessel and all vessels are within beams are inaccurate. We postulate that vessels outside beams may be relatively more vulnerable to mechanical compression by elevated IOP than are vessels shielded inside of beams.
Collapse
Affiliation(s)
- Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Bryn L. Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA,Department of Engineering, Duquesne University, Pittsburgh, PA, USA
| | - Po-Yi Lee
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Alexandra L. Gogola
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Po Lam
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Andrew P. Voorhees
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA
| | - Joseph F. Rizzo
- Neuro-Ophthalmology Service, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA,Neuro-Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston, MA, USA
| | - Tatjana C. Jakobs
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary/Schepens Eye Research Institute, Harvard Medical School, Boston, MA, USA
| | - Ian A. Sigal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh PA, USA,Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh PA, USA,Correspondence: Ian A. Sigal, Ph.D., Laboratory of Ocular Biomechanics, Department of Ophthalmology, University of Pittsburgh Medical Center, 203 Lothrop St. Rm. 930, Pittsburgh, PA, USA. 15213, Phone: (412) 864-2220; fax: (412) 647-5880, www.OcularBiomechanics.org
| |
Collapse
|
16
|
G. K. AV, Gogoi G, Behera B, Rila S, Rangarajan A, Pandya HJ. RapidET: a MEMS-based platform for label-free and rapid demarcation of tumors from normal breast biopsy tissues. MICROSYSTEMS & NANOENGINEERING 2022; 8:1. [PMID: 35087680 PMCID: PMC8761751 DOI: 10.1038/s41378-021-00337-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 11/07/2021] [Accepted: 11/28/2021] [Indexed: 05/09/2023]
Abstract
The rapid and label-free diagnosis of malignancies in ex vivo breast biopsy tissues has significant utility in pathology laboratories and operating rooms. We report a MEMS-based platform integrated with microchips that performs phenotyping of breast biopsy tissues using electrothermal sensing. The microchip, fabricated on a silicon substrate, incorporates a platinum microheater, interdigitated electrodes (IDEs), and resistance temperature detectors (RTDs) as on-chip sensing elements. The microchips are integrated onto the platform using a slide-fit contact enabling quick replacement for biological measurements. The bulk resistivity (ρ B ), surface resistivity (ρ S ), and thermal conductivity (k) of deparaffinized and formalin-fixed paired tumor and adjacent normal breast biopsy samples from N = 8 patients were measured. For formalin-fixed samples, the mean ρ B for tumors showed a statistically significant fold change of 4.42 (P = 0.014) when the tissue was heated from 25 °C to 37 °C compared to the adjacent normal tissue, which showed a fold change of 3.47. The mean ρ S measurements also showed a similar trend. The mean k of the formalin-fixed tumor tissues was 0.309 ± 0.02 W m-1 K-1 compared to a significantly higher k of 0.563 ± 0.028 W m-1 K-1 for the adjacent normal tissues. A similar trend was observed in ρ B, ρ S, and k for the deparaffinized tissue samples. An analysis of a combination of ρ B , ρ S , and k using Fisher's combined probability test and linear regression suggests the advantage of using all three parameters simultaneously for distinguishing tumors from adjacent normal tissues with higher statistical significance.
Collapse
Affiliation(s)
- Anil Vishnu G. K.
- Center for BioSystems Science and Engineering, Indian Institute of Science, Bangalore, Karnataka India
| | - Gayatri Gogoi
- Department of Pathology, Assam Medical College, Dibrugarh, Assam India
| | - Bhagaban Behera
- Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore, Karnataka India
| | - Saeed Rila
- Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore, Karnataka India
| | - Annapoorni Rangarajan
- Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore, Karnataka India
| | - Hardik J. Pandya
- Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore, Karnataka India
- Centre for Product Design and Manufacturing, Indian Institute of Science, Bangalore, Karnataka India
| |
Collapse
|
17
|
Zhu Z, Waxman S, Wang B, Wallace J, Schmitt SE, Tyler-Kabara E, Ishikawa H, Schuman JS, Smith MA, Wollstein G, Sigal IA. Interplay between intraocular and intracranial pressure effects on the optic nerve head in vivo. Exp Eye Res 2021; 213:108809. [PMID: 34736887 DOI: 10.1016/j.exer.2021.108809] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 10/19/2021] [Accepted: 10/25/2021] [Indexed: 12/19/2022]
Abstract
Intracranial pressure (ICP) has been proposed to play an important role in the sensitivity to intraocular pressure (IOP) and susceptibility to glaucoma. However, the in vivo effects of simultaneous, controlled, acute variations in ICP and IOP have not been directly measured. We quantified the deformations of the anterior lamina cribrosa (ALC) and scleral canal at Bruch's membrane opening (BMO) under acute elevation of IOP and/or ICP. Four eyes of three adult monkeys were imaged in vivo with OCT under four pressure conditions: IOP and ICP either at baseline or elevated. The BMO and ALC were reconstructed from manual delineations. From these, we determined canal area at the BMO (BMO area), BMO aspect ratio and planarity, and ALC median depth relative to the BMO plane. To better account for the pressure effects on the imaging, we also measured ALC visibility as a percent of the BMO area. Further, ALC depths were analyzed only in regions where the ALC was visible in all pressure conditions. Bootstrap sampling was used to obtain mean estimates and confidence intervals, which were then used to test for significant effects of IOP and ICP, independently and in interaction. Response to pressure manipulation was highly individualized between eyes, with significant changes detected in a majority of the parameters. Significant interactions between ICP and IOP occurred in all measures, except ALC visibility. On average, ICP elevation expanded BMO area by 0.17 mm2 at baseline IOP, and contracted BMO area by 0.02 mm2 at high IOP. ICP elevation decreased ALC depth by 10 μm at baseline IOP, but increased depth by 7 μm at high IOP. ALC visibility decreased as ICP increased, both at baseline (-10%) and high IOP (-17%). IOP elevation expanded BMO area by 0.04 mm2 at baseline ICP, and contracted BMO area by 0.09 mm2 at high ICP. On average, IOP elevation caused the ALC to displace 3.3 μm anteriorly at baseline ICP, and 22 μm posteriorly at high ICP. ALC visibility improved as IOP increased, both at baseline (5%) and high ICP (8%). In summary, changing IOP or ICP significantly deformed both the scleral canal and the lamina of the monkey ONH, regardless of the other pressure level. There were significant interactions between the effects of IOP and those of ICP on LC depth, BMO area, aspect ratio and planarity. On most eyes, elevating both pressures by the same amount did not cancel out the effects. Altogether our results show that ICP affects sensitivity to IOP, and thus that it can potentially also affect susceptibility to glaucoma.
Collapse
Affiliation(s)
- Ziyi Zhu
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Susannah Waxman
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bo Wang
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha E Schmitt
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Elizabeth Tyler-Kabara
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurosurgery, University of Texas-Austin, Austin, TX, USA
| | - Hiroshi Ishikawa
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Joel S Schuman
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Matthew A Smith
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Gadi Wollstein
- Department of Ophthalmology, NYU School of Medicine, New York, NY, USA
| | - Ian A Sigal
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA.
| |
Collapse
|
18
|
Kawashima T, Sato F. First in situ 3D visualization of the human cardiac conduction system and its transformation associated with heart contour and inclination. Sci Rep 2021; 11:8636. [PMID: 33883659 PMCID: PMC8060315 DOI: 10.1038/s41598-021-88109-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023] Open
Abstract
Current advanced imaging modalities with applied tracing and processing techniques provide excellent visualization of almost all human internal structures in situ; however, the actual 3D internal arrangement of the human cardiac conduction system (CCS) is still unknown. This study is the first to document the successful 3D visualization of the CCS from the sinus node to the bundle branches within the human body, based on our specialized physical micro-dissection and its CT imaging. The 3D CCS transformation by cardiac inclination changes from the standing to the lying position is also provided. Both actual dissection and its CT image-based simulation identified that when the cardiac inclination changed from standing to lying, the sinus node shifted from the dorso-superior to the right outer position and the atrioventricular conduction axis changed from a vertical to a leftward horizontal position. In situ localization of the human CCS provides accurate anatomical localization with morphometric data, and it indicates the useful correlation between heart inclination and CCS rotation axes for predicting the variable and invisible human CCS in the living body. Advances in future imaging modalities and methodology are essential for further accurate in situ 3D CCS visualization.
Collapse
Affiliation(s)
- Tomokazu Kawashima
- Department of Anatomy, School of Medicine, Toho University, 5-21-16 Omori-Nishi, Ota-ku, Tokyo, 143-8540, Japan.
| | - Fumi Sato
- Department of Anatomy, School of Medicine, Toho University, 5-21-16 Omori-Nishi, Ota-ku, Tokyo, 143-8540, Japan
| |
Collapse
|
19
|
Andersen SB, Taghavi I, Hoyos CAV, Søgaard SB, Gran F, Lönn L, Hansen KL, Jensen JA, Nielsen MB, Sørensen CM. Super-Resolution Imaging with Ultrasound for Visualization of the Renal Microvasculature in Rats Before and After Renal Ischemia: A Pilot Study. Diagnostics (Basel) 2020; 10:diagnostics10110862. [PMID: 33105888 PMCID: PMC7690607 DOI: 10.3390/diagnostics10110862] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/20/2020] [Accepted: 10/21/2020] [Indexed: 12/22/2022] Open
Abstract
In vivo monitoring of the microvasculature is relevant since diseases such as diabetes, ischemia, or cancer cause microvascular impairment. Super-resolution ultrasound imaging allows in vivo examination of the microvasculature by detecting and tracking sparsely distributed intravascular microbubbles over a minute-long period. The ability to create detailed images of the renal vasculature of Sprague-Dawley rats using a modified clinical ultrasound platform was investigated in this study. Additionally, we hypothesized that early ischemic damage to the renal microcirculation could be visualized. After a baseline scan of the exposed kidney, 10 rats underwent clamping of the renal vein (n = 5) or artery (n = 5) for 45 min. The kidneys were rescanned at the onset of clamp release and after 60 min of reperfusion. Using a processing pipeline for tissue motion compensation and microbubble tracking, super-resolution images with a very high level of detail were constructed. Image filtration allowed further characterization of the vasculature by isolating specific vessels such as the ascending vasa recta with a 15–20 μm diameter. Using the super-resolution images alone, it was only possible for six assessors to consistently distinguish the healthy renal microvasculature from the microvasculature at the onset of vein clamp release. Future studies will aim at attaining quantitative estimations of alterations in the renal microvascular blood flow using super-resolution ultrasound imaging.
Collapse
Affiliation(s)
- Sofie Bech Andersen
- Department of Radiology, Rigshospitalet, 2100 Copenhagen, Denmark; (S.B.S.); (L.L.); (K.L.H.); (M.B.N.)
- Department of Biomedical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark;
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
- Correspondence:
| | - Iman Taghavi
- Center for Fast Ultrasound Imaging, Department of Health Technology, Technical University of Denmark, 2800 Lyngby, Denmark; (I.T.); (J.A.J.)
| | | | - Stinne Byrholdt Søgaard
- Department of Radiology, Rigshospitalet, 2100 Copenhagen, Denmark; (S.B.S.); (L.L.); (K.L.H.); (M.B.N.)
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Fredrik Gran
- BK Medical ApS, 2730 Herlev, Denmark; (C.A.V.H.); (F.G.)
| | - Lars Lönn
- Department of Radiology, Rigshospitalet, 2100 Copenhagen, Denmark; (S.B.S.); (L.L.); (K.L.H.); (M.B.N.)
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Kristoffer Lindskov Hansen
- Department of Radiology, Rigshospitalet, 2100 Copenhagen, Denmark; (S.B.S.); (L.L.); (K.L.H.); (M.B.N.)
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Jørgen Arendt Jensen
- Center for Fast Ultrasound Imaging, Department of Health Technology, Technical University of Denmark, 2800 Lyngby, Denmark; (I.T.); (J.A.J.)
| | - Michael Bachmann Nielsen
- Department of Radiology, Rigshospitalet, 2100 Copenhagen, Denmark; (S.B.S.); (L.L.); (K.L.H.); (M.B.N.)
- Department of Clinical Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | | |
Collapse
|
20
|
Alkemade A, Pine K, Kirilina E, Keuken MC, Mulder MJ, Balesar R, Groot JM, Bleys RLAW, Trampel R, Weiskopf N, Herrler A, Möller HE, Bazin PL, Forstmann BU. 7 Tesla MRI Followed by Histological 3D Reconstructions in Whole-Brain Specimens. Front Neuroanat 2020; 14:536838. [PMID: 33117133 PMCID: PMC7574789 DOI: 10.3389/fnana.2020.536838] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 09/14/2020] [Indexed: 11/24/2022] Open
Abstract
Post mortem magnetic resonance imaging (MRI) studies on the human brain are of great interest for the validation of in vivo MRI. It facilitates a link between functional and anatomical information available from MRI in vivo and neuroanatomical knowledge available from histology/immunocytochemistry. However, linking in vivo and post mortem MRI to microscopy techniques poses substantial challenges. Fixation artifacts and tissue deformation of extracted brains, as well as co registration of 2D histology to 3D MRI volumes complicate direct comparison between modalities. Moreover, post mortem brain tissue does not have the same physical properties as in vivo tissue, and therefore MRI approaches need to be adjusted accordingly. Here, we present a pipeline in which whole-brain human post mortem in situ MRI is combined with subsequent tissue processing of the whole human brain, providing a 3-dimensional reconstruction via blockface imaging. To this end, we adapted tissue processing procedures to allow both post mortem MRI and subsequent histological and immunocytochemical processing. For MRI, tissue was packed in a susceptibility matched solution, tailored to fit the dimensions of the MRI coil. Additionally, MRI sequence parameters were adjusted to accommodate T1 and T2∗ shortening, and scan time was extended, thereby benefiting the signal-to-noise-ratio that can be achieved using extensive averaging without motion artifacts. After MRI, the brain was extracted from the skull and subsequently cut while performing optimized blockface imaging, thereby allowing three-dimensional reconstructions. Tissues were processed for Nissl and silver staining, and co-registered with the blockface images. The combination of these techniques allows direct comparisons across modalities.
Collapse
Affiliation(s)
- Anneke Alkemade
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands
| | - Kerrin Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Evgeniya Kirilina
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Neurocomputation and Neuroimaging Unit, Department of Psychology and Educational Science, Free University Berlin, Berlin, Germany
| | - Max C Keuken
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands
| | - Martijn J Mulder
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands.,Department of Experimental Psychology, Utrecht University, Utrecht, Netherlands
| | - Rawien Balesar
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands.,The Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, Netherlands
| | - Josephine M Groot
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands
| | - Ronald L A W Bleys
- Department of Anatomy, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands
| | - Robert Trampel
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Andreas Herrler
- Department of Anatomy and Embryology, Maastricht University, Maastricht, Netherlands
| | - Harald E Möller
- NMR Methods & Development Group, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Pierre-Louis Bazin
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands.,Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.,Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Birte U Forstmann
- Integrative Model-Based Neuroscience Research Unit, University of Amsterdam, Amsterdam, Netherlands
| |
Collapse
|
21
|
De la Cruz Pino JG, Morales Mávil JE, Sánchez García ADC, Hernandez-Baltazar D. Optimized technique to extract and fix Olive ridley turtle hatchling retina for histological study. Acta Histochem 2020; 122:151592. [PMID: 32778246 DOI: 10.1016/j.acthis.2020.151592] [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: 10/02/2019] [Revised: 06/06/2020] [Accepted: 07/03/2020] [Indexed: 10/23/2022]
Abstract
The efficient extraction and fixation of a tissue allows in preserving the cytoarchitecture, chemical composition and tissue organization, which is key in physiological and histopathological studies. The main goal of this study was to establish a microsurgery technique to obtain ocular tissue and provide an optimized immersion fixation protocol based on the 10 % formalin-intraocular injection on Olive ridley sea turtle hatchlings (Lepidochelys olivacea). To evaluate this optimized technique, a histological comparison between traditional immersion and intraocular/immersion protocols was done. The eyeball were processed into five protocols: Frozen eyes (Group 1), frozen eyes immersed in 10 % formalin (Group 2), fresh eyes immersed in 10 % formalin (Group 3), fresh eyes intraocularly injected with 0.1 M phosphate buffer solution (PBS) and then immersed in 10 % formalin (Group 4), and fresh eyes fixed by 10 % formalin-intraocular followed by 10 % formalin-immersion (Group 5). In comparison with all groups evaluated, the intraocular/immersion fixation protocol lead the conservation of eyeball shape, cell integrity and maintenance of the organization of the retina layers of sea turtle hatchlings. If this method will be the key in studying sea turtle, we suppose that this procedure, with minimal adjustments, could be useful in animals with similar eye anatomy.
Collapse
|
22
|
Hutson KA, Pulver SH, Ariel P, Naso C, Fitzpatrick DC. Light sheet microscopy of the gerbil cochlea. J Comp Neurol 2020; 529:757-785. [PMID: 32632959 DOI: 10.1002/cne.24977] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 05/13/2020] [Accepted: 06/21/2020] [Indexed: 01/19/2023]
Abstract
Light sheet fluorescence microscopy (LSFM) provides a rapid and complete three-dimensional image of the cochlea. The method retains anatomical relationships-on a micrometer scale-between internal structures such as hair cells, basilar membrane (BM), and modiolus with external surface structures such as the round and oval windows. Immunolabeled hair cells were used to visualize the spiraling BM in the intact cochlea without time intensive dissections or additional histological processing; yet material prepared for LSFM could be rehydrated, the BM dissected out and reimaged at higher resolution with the confocal microscope. In immersion-fixed material, details of the cochlear vasculature were seen throughout the cochlea. Hair cell counts (both inner and outer) as well as frequency maps of the BM were comparable to those obtained by other methods, but with the added dimension of depth. The material provided measures of angular, linear, and vector distance between characteristic frequency regions along the BM. Thus, LSFM provides a unique ability to rapidly image the entire cochlea in a manner applicable to model and interpret physiological results. Furthermore, the three-dimensional organization of the cochlea can be studied at the organ and cellular level with LSFM, and this same material can be taken to the confocal microscope for detailed analysis at the subcellular level.
Collapse
Affiliation(s)
- Kendall A Hutson
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Stephen H Pulver
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Pablo Ariel
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Caroline Naso
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Douglas C Fitzpatrick
- Department of Otolaryngology/Head and Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| |
Collapse
|
23
|
Challenges of Post-measurement Histology for the Dielectric Characterisation of Heterogeneous Biological Tissues. SENSORS 2020; 20:s20113290. [PMID: 32526983 PMCID: PMC7309042 DOI: 10.3390/s20113290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 06/05/2020] [Accepted: 06/08/2020] [Indexed: 12/28/2022]
Abstract
The dielectric properties of biological tissues are typically measured using the open-ended coaxial probe technique, which is based on the assumption that the tissue sample is homogeneous. Therefore, for heterogeneous tissue samples, additional post-measurement sample processing is conducted. Specifically, post-measurement histological analysis may be performed in order to associate the measured dielectric properties with the tissue types present in a heterogeneous sample. Accurate post-measurement histological analysis enables identification of the constituent tissue types that contributed to the measured dielectric properties, and their relative distributions. There is no standard protocol for conducting post-measurement histological analysis, which leads to high numbers of excluded tissue samples and inconsistencies in the resulting reported data for heterogeneous tissues. To this extent, this study examines the post-measurement histological process and the challenges in associating the acquired dielectric properties with the different tissue types present in heterogeneous samples. The results demonstrate that the histological process inevitably alters the morphology of samples, thus introducing errors in the interpretation of the dielectric properties acquired from heterogeneous biological samples. Notably, sample size was seen to shrink by up to 90% through the histological process, meaning that sensing volume determined from fresh tissues is not directly applicable to histology images.
Collapse
|
24
|
Lee SL, He MY, Chen YF, Dong CY. Quantification of collagen structural changes during chick corneal development. JOURNAL OF BIOPHOTONICS 2020; 13:e201900144. [PMID: 31465146 DOI: 10.1002/jbio.201900144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 06/10/2023]
Abstract
As the most abundant structural mammalian protein, collagen has been implicated in the pathogenesis of numerous diseases such as osteogenesis imperfecta, and cancer. In the case of cornea, abnormal cornea development can lead to conditions such as agenesis, megalocornea, microcornea, and cornea plana. Therefore, understanding the mechanisms of collagen assembly during development may contribute to the prevention or treatment of corneal diseases. In this study, we applied fast Fourier transform second harmonic generation microscopy to quantify parameters of corneal structures during chick development. Our results show that both the rotational pitch and overall rotational angle of corneal stroma modulate between E9 and E19. In addition, we found that corneal structures between left and right corneas are highly correlated during development.
Collapse
Affiliation(s)
- Sheng-Lin Lee
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Ming-Ye He
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Yang-Fang Chen
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Chen-Yuan Dong
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| |
Collapse
|
25
|
Gogola A, Jan NJ, Lathrop KL, Sigal IA. Radial and Circumferential Collagen Fibers Are a Feature of the Peripapillary Sclera of Human, Monkey, Pig, Cow, Goat, and Sheep. Invest Ophthalmol Vis Sci 2019; 59:4763-4774. [PMID: 30304458 PMCID: PMC6166897 DOI: 10.1167/iovs.18-25025] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Purpose To test the hypothesis that human, monkey, pig, sheep, cow, and goat eyes exhibit circumferential, radial, and interweaving collagen architecture in the posterior sclera. Methods We analyzed 1,327 cryosections from the posterior poles of 4 human, 4 monkey, 5 pig, 8 sheep, 1 goat, and 2 cow eyes. Images were acquired using polarized light microscopy and processed to obtain polar fiber orientations relative to the center of the canal. Circumferential, radial, and interweaving regions were identified and analyzed for mean fiber orientation and anisotropy and region width and thickness. Results Every eye exhibited circumferential, radial, and interweaving fibers in consistent locations. Radial fibers extended out from near the canal into the peripapillary and peripheral sclera in the innermost sclera. Circumferential fibers were directly adjacent to the canal and most prevalent in the outermost, posterior sclera. Interweaving fibers were found throughout the sclera thickness. Across all species, median anisotropy in the radial, circumferential, and interweaving regions were 0.95, 0.96, and 0.28, respectively. Conclusions Regions of radial, circumferential, and interweaving fibers occur in the posterior pole sclera of human, monkey, pig, sheep, cow, and goat eyes. The consistency across species in scleral architecture suggests that they are primary organizational components whose functions should be better understood.
Collapse
Affiliation(s)
- Alexandra Gogola
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Kira L Lathrop
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
26
|
Brazile BL, Hua Y, Jan NJ, Wallace J, Gogola A, Sigal IA. Thin Lamina Cribrosa Beams Have Different Collagen Microstructure Than Thick Beams. Invest Ophthalmol Vis Sci 2019; 59:4653-4661. [PMID: 30372734 PMCID: PMC6149225 DOI: 10.1167/iovs.18-24763] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose To compare the collagen microstructural crimp characteristics between thin and thick lamina cribrosa (LC) beams. Methods Seven eyes from four sheep were fixed at 5 mm Hg IOP in 10% formalin. For each eye, one to three coronal cryosections through the LC were imaged with polarized light microscopy and analyzed to visualize the LC and determine collagen fiber microstructure. For every beam, we measured its width and three characteristics of the crimp of its collagen fibers: waviness, tortuosity, and amplitude. Linear mixed effects models were used to test whether crimp characteristics were associated with the LC beam width. Results For each eye and over all the eyes, LC beam width was positively associated with crimp waviness and tortuosity, and negatively associated with crimp amplitude (P's < 0.0001). Thin beams, average width 13.11 μm, had average (SD) waviness, tortuosity, and amplitude of 0.27 (0.17) radians, 1.017 (0.028) and 1.88 (1.41) μm, respectively. For thick beams, average width 26.10 μm, these characteristics were 0.33 (0.18) radians, 1.025 (0.037) and 1.58 (1.36) μm, respectively. Conclusions Our results suggest heterogeneity in LC beam mechanical properties. Thin beams were less wavy than their thicker counterparts, suggesting that thin beams may stiffen at lower IOP than thick beams. This difference may allow thin beams to support similar amounts of IOP-induced force as thicker beams, thus providing a similar level of structural support to the axons at physiologic IOP, despite the differences in width. Measurements of beam-level mechanical properties are needed to confirm these predictions.
Collapse
Affiliation(s)
- Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Alexandra Gogola
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,The Louis J. Fox Center for Vision Restoration of UPMC and the University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
27
|
Mercatelli R, Mattana S, Capozzoli L, Ratto F, Rossi F, Pini R, Fioretto D, Pavone FS, Caponi S, Cicchi R. Morpho-mechanics of human collagen superstructures revealed by all-optical correlative micro-spectroscopies. Commun Biol 2019; 2:117. [PMID: 30937399 PMCID: PMC6435656 DOI: 10.1038/s42003-019-0357-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 02/05/2019] [Indexed: 12/18/2022] Open
Abstract
In every biological tissue, morphological and topological properties strongly affect its mechanical features and behaviour, so that ultrastructure, composition and mechanical parameters are intimately connected. Overall, it is their correct interplay that guarantees the tissue functionality. The development of experimental methods able to correlate these properties would open new opportunities both in the biological and the biomedical fields. Here, we report a correlative study intended to map supramolecular morphology, biochemical composition and viscoelastic parameters of collagen by all-optical microscopies. In particular, using human corneal tissue as a benchmark, we correlate Second-Harmonic Generation maps with mechanical and biochemical imaging obtained by Brillouin and Raman micro-spectroscopy. The study highlights how subtle variations in supramolecular organization originate the peculiar mechanical behavior of different subtypes of corneal lamellae. The presented methodology paves the way to the non-invasive assessment of tissue morpho-mechanics in biological as well as synthetic materials.
Collapse
Affiliation(s)
- Raffaella Mercatelli
- National Institute of Optics, National Research Council (CNR-INO), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
| | - Sara Mattana
- National Institute of Optics, National Research Council (CNR-INO), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
- Department of Physics and Geology, University of Perugia, Via Alessandro Pascoli, I-06123 Perugia, Italy
| | - Laura Capozzoli
- Institute of Applied Physics “Nello Carrara”, National Research Council (CNR-IFAC), Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy
- Center of Electron Microscopy “Laura Bonzi” (Ce.M.E), Institute of Chemistry of Organometallic Compounds, National Research Council (CNR-ICCOM), Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy
| | - Fulvio Ratto
- Institute of Applied Physics “Nello Carrara”, National Research Council (CNR-IFAC), Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy
| | - Francesca Rossi
- Institute of Applied Physics “Nello Carrara”, National Research Council (CNR-IFAC), Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy
| | - Roberto Pini
- Institute of Applied Physics “Nello Carrara”, National Research Council (CNR-IFAC), Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy
| | - Daniele Fioretto
- Department of Physics and Geology, University of Perugia, Via Alessandro Pascoli, I-06123 Perugia, Italy
- CEMIN-Center of Excellence for Innovative Nanostructured Material, Via Alessandro Pascoli, I-06123 Perugia, Italy
| | - Francesco Saverio Pavone
- National Institute of Optics, National Research Council (CNR-INO), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
- European Laboratory for Non-linear Spectroscopy (LENS), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
- Department of Physics, University of Florence, Via Giovanni Sansone 1, I-50019 Sesto Fiorentino, Italy
| | - Silvia Caponi
- Institute of Materials, National Research Council (CNR-IOM), Unit of Perugia, c/o Department of Physics and Geology, University of Perugia, Via A. Pascoli, I-06123 Perugia, Italy
| | - Riccardo Cicchi
- National Institute of Optics, National Research Council (CNR-INO), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
- European Laboratory for Non-linear Spectroscopy (LENS), Via Nello Carrara 1, I-50019 Sesto Fiorentino, Italy
| |
Collapse
|
28
|
Wang X, Teoh CKG, Chan ASY, Thangarajoo S, Jonas JB, Girard MJA. Biomechanical Properties of Bruch's Membrane-Choroid Complex and Their Influence on Optic Nerve Head Biomechanics. Invest Ophthalmol Vis Sci 2019; 59:2808-2817. [PMID: 30029276 DOI: 10.1167/iovs.17-22069] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of this study was to measure the rupture pressure and the biomechanical properties of porcine Bruch's membrane (BM)-choroid complex (BMCC) and the influences of BM on optic nerve head (ONH) tissues. Methods The biomechanical properties of BMCC were extracted through uniaxial tensile tests of 10 BMCC specimens from 10 porcine eyes; the rupture pressures of BMCC were measured through burst tests of 20 porcine eyes; and the influence of BM on IOP-induced ONH deformations were investigated using finite element (FE) analysis. Results Uniaxial experimental results showed that the average elastic (tangent) moduli of BMCC samples at 0% and 5% strain were 1.60 ± 0.81 and 2.44 ± 1.02 MPa, respectively. Burst tests showed that, on average, BMCC could sustain an IOP of 82 mm Hg before rupture. FE simulation results predicted that, under elevated IOP, prelamina tissue strains increased with increasing BM stiffness. On the contrary, lamina cribrosa strains showed an opposite trend but the effects were small. Conclusions BMCC stiffness is comparable or higher than those of other ocular tissues and can sustain a relatively high pressure before rupture. Additionally, BM may have a nonnegligible influence on IOP-induced ONH deformations.
Collapse
Affiliation(s)
- Xiaofei Wang
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Clarence Ken Guan Teoh
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Anita S Y Chan
- Translational Ophthalmic Pathology, Singapore Eye Research Institute, Ophthalmic Pathology Service, Singapore National Eye Centre, Singapore.,Duke-National University of Singapore Medical School, Singapore
| | - Sathiyan Thangarajoo
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore
| | - Jost B Jonas
- Department of Ophthalmology, Medical Faculty Mannheim of the Ruprecht-Karls-University, Heidelberg, Germany.,Beijing Institute of Ophthalmology, Beijing Tongren Eye Centre, Beijing Tongren Hospital, Capital Medical University, and Beijing Key Laboratory of Ophthalmology and Visual Sciences, Beijing, China
| | - Michaël J A Girard
- Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore.,Translational Ophthalmic Pathology, Singapore Eye Research Institute, Ophthalmic Pathology Service, Singapore National Eye Centre, Singapore
| |
Collapse
|
29
|
Gogola A, Jan NJ, Brazile B, Lam P, Lathrop KL, Chan KC, Sigal IA. Spatial Patterns and Age-Related Changes of the Collagen Crimp in the Human Cornea and Sclera. Invest Ophthalmol Vis Sci 2019; 59:2987-2998. [PMID: 30025116 PMCID: PMC5995484 DOI: 10.1167/iovs.17-23474] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Purpose Collagen is the main load-bearing component of the eye, and collagen crimp is a critical determinant of tissue mechanical behavior. We test the hypothesis that collagen crimp morphology varies over the human cornea and sclera and with age. Methods We analyzed 42 axial whole-globe sections from 20 normal eyes of 20 human donors, ranging in age from 0.08 (1 month) to 97 years. The sections were imaged using polarized light microscopy to obtain μm-scale fiber bundle/lamellae orientation from two corneal and six scleral regions. Crimp morphology was quantified through waviness, tortuosity, and amplitude. Results Whole-globe median waviness, tortuosity, and amplitude were 0.127 radians, 1.002, and 0.273 μm, respectively. These parameters, however, were not uniform over the globe, instead exhibiting distinct, consistent patterns. All crimp parameters decreased significantly with age, with significantly different age-related decreases between regions. The crimp morphology of the limbus changed the most drastically with age, such that it had the largest crimp in neonates, and among the smallest in the elderly. Conclusions Age-related decreases in crimp parameters are likely one of the mechanisms underlying age-related stiffening of the sclera and cornea, potentially influencing sensitivity to IOP. Further work is needed to determine the biomechanical implications of the crimp patterns observed. The comparatively large changes in the crimp morphology of the limbus, especially in the early years of life, suggest that crimp in this region may play a role in eye development, although the exact nature of this is unclear.
Collapse
Affiliation(s)
- Alexandra Gogola
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Bryn Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Po Lam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Kira L Lathrop
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Kevin C Chan
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Ophthalmology, New York University, New York, New York, United States.,Department of Radiology, New York University, New York, New York, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States.,Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
30
|
Yang B, Brazile B, Jan NJ, Hua Y, Wei J, Sigal IA. Structured polarized light microscopy for collagen fiber structure and orientation quantification in thick ocular tissues. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-10. [PMID: 30277032 PMCID: PMC6210789 DOI: 10.1117/1.jbo.23.10.106001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 09/13/2018] [Indexed: 05/07/2023]
Abstract
Collagen is a major constituent of the eye and understanding its architecture and biomechanics is critical to preserve and restore vision. We, recently, demonstrated polarized light microscopy (PLM) as a powerful technique for measuring properties of the collagen fibers of the eye, such as spatial distribution and orientation. Our implementation of PLM, however, required sectioning the tissues for imaging using transmitted light. This is problematic because it limits analysis to thin sections. This is not only slow, but precludes study of dynamic events such as pressure-induced deformations, which are central to the role of collagen. We introduce structured polarized light microscopy (SPLM), an imaging technique that combines structured light illumination with PLM to allow imaging and measurement of collagen fiber properties in thick ocular tissues. Using pig and sheep eyes, we show that SPLM rejects diffuse background light effectively in thick tissues, significantly enhancing visualization of optic nerve head (ONH) structures, such as the lamina cribrosa, and improving the accuracy of the collagen fiber orientation measurements. Further, we demonstrate the integration of SPLM with an inflation device to enable direct visualization, deformation tracking, and quantification of collagen fibers in ONHs while under controlled pressure.
Collapse
Affiliation(s)
- Bin Yang
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
| | - Bryn Brazile
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
| | - Ning-Jiun Jan
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
- University of Pittsburgh, Department of Bioengineering, Pittsburgh, Pennsylvania, United States
| | - Yi Hua
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
| | - Junchao Wei
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
| | - Ian A. Sigal
- University of Pittsburgh School of Medicine, Department of Ophthalmology, Pittsburgh, Pennsylvania, United States
- University of Pittsburgh, Department of Bioengineering, Pittsburgh, Pennsylvania, United States
| |
Collapse
|
31
|
Yang B, Jan NJ, Brazile B, Voorhees A, Lathrop KL, Sigal IA. Polarized light microscopy for 3-dimensional mapping of collagen fiber architecture in ocular tissues. JOURNAL OF BIOPHOTONICS 2018. [PMID: 29633576 DOI: 10.1002/jbio.2018.11.issue-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Collagen fibers play a central role in normal eye mechanics and pathology. In ocular tissues, collagen fibers exhibit a complex 3-dimensional (3D) fiber orientation, with both in-plane (IP) and out-of-plane (OP) orientations. Imaging techniques traditionally applied to the study of ocular tissues only quantify IP fiber orientation, providing little information on OP fiber orientation. Accurate description of the complex 3D fiber microstructures of the eye requires quantifying full 3D fiber orientation. Herein, we present 3dPLM, a technique based on polarized light microscopy developed to quantify both IP and OP collagen fiber orientations of ocular tissues. The performance of 3dPLM was examined by simulation and experimental verification and validation. The experiments demonstrated an excellent agreement between extracted and true 3D fiber orientation. Both IP and OP fiber orientations can be extracted from the sclera and the cornea, providing previously unavailable quantitative 3D measures and insight into the tissue microarchitecture. Together, the results demonstrate that 3dPLM is a powerful imaging technique for the analysis of ocular tissues.
Collapse
Affiliation(s)
- Bin Yang
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Bryn Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Andrew Voorhees
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Kira L Lathrop
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania
| |
Collapse
|
32
|
Yang B, Jan NJ, Brazile B, Voorhees A, Lathrop KL, Sigal IA. Polarized light microscopy for 3-dimensional mapping of collagen fiber architecture in ocular tissues. JOURNAL OF BIOPHOTONICS 2018; 11:e201700356. [PMID: 29633576 PMCID: PMC6105457 DOI: 10.1002/jbio.201700356] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 04/03/2018] [Indexed: 05/20/2023]
Abstract
Collagen fibers play a central role in normal eye mechanics and pathology. In ocular tissues, collagen fibers exhibit a complex 3-dimensional (3D) fiber orientation, with both in-plane (IP) and out-of-plane (OP) orientations. Imaging techniques traditionally applied to the study of ocular tissues only quantify IP fiber orientation, providing little information on OP fiber orientation. Accurate description of the complex 3D fiber microstructures of the eye requires quantifying full 3D fiber orientation. Herein, we present 3dPLM, a technique based on polarized light microscopy developed to quantify both IP and OP collagen fiber orientations of ocular tissues. The performance of 3dPLM was examined by simulation and experimental verification and validation. The experiments demonstrated an excellent agreement between extracted and true 3D fiber orientation. Both IP and OP fiber orientations can be extracted from the sclera and the cornea, providing previously unavailable quantitative 3D measures and insight into the tissue microarchitecture. Together, the results demonstrate that 3dPLM is a powerful imaging technique for the analysis of ocular tissues.
Collapse
Affiliation(s)
- Bin Yang
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bryn Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Andrew Voorhees
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Kira L. Lathrop
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| |
Collapse
|
33
|
Jan NJ, Sigal IA. Collagen fiber recruitment: A microstructural basis for the nonlinear response of the posterior pole of the eye to increases in intraocular pressure. Acta Biomater 2018; 72:295-305. [PMID: 29574185 DOI: 10.1016/j.actbio.2018.03.026] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 03/09/2018] [Accepted: 03/14/2018] [Indexed: 01/27/2023]
Abstract
Our goal was to quantify and characterize how the collagen fiber crimp waviness of the lamina cribrosa (LC) and peripapillary sclera (PPS) changes with intraocular pressure (IOP). Thirteen sheep (ovine) eyes were immersion and perfusion fixed while maintaining IOP at 0, 10, 15, 20, or 50 mmHg. Coronal optic nerve head (ONH) sections (30 µm) were imaged with polarized light microscopy (PLM) and analyzed for collagen fiber orientation and waviness (SD of fiber orientation). In the LC, the waviness of every LC beam was measured. In the PPS, at least 900 collagen bundles were measured per eye. Using the waviness at 50 mmHg IOP, we defined tissue-specific thresholds to determine the fraction of loaded or recruited fibers. We found that fiber waviness decreased with IOP (P < 0.001). At every IOP, the waviness of the collagen fibers, and the fraction of fibers recruited in the LC were smaller or equal than those of the PPS (P < 0.001). At 15 mmHg IOP, both LC and PPS had ¾ recruited fibers and ¼ left in reserve. The decreased waviness with IOP and associated fiber recruitment is experimental evidence of fiber-based nonlinear biomechanical behavior of the ONH. At all IOPs the PPS had an equal or larger fraction of fibers recruited than the LC. That both LC and PPS had the same fraction of recruited and reserve fibers at normal IOP suggests that this may be an optimal fraction of recruitment for healthy eyes. Whether this extends to human eyes remains unknown. STATEMENT OF SIGNIFICANCE Collagen fibers exhibit a natural waviness or crimp that largely determine the nonlinear biomechanics of soft tissue. Experimental measurements of crimp morphology in the sheep eye, and how it changes with intraocular pressure (IOP), however, are exceedingly sparse. We quantified how posterior eye crimp changes with increasing IOP. We found that the lamina cribrosa and peripapillary sclera have fundamentally different crimp, and with increasing IOP, have different proportions of fibers that straighten, or get recruited, versus remaining wavy, or in reserve. Interestingly, at physiologic IOP of 15 mmHg, both tissues had about ¾ fibers recruited and ¼ fibers in reserve, indicating there may be an optimal fraction of fibers.
Collapse
|
34
|
Jan NJ, Brazile BL, Hu D, Grube G, Wallace J, Gogola A, Sigal IA. Crimp around the globe; patterns of collagen crimp across the corneoscleral shell. Exp Eye Res 2018; 172:159-170. [PMID: 29660327 DOI: 10.1016/j.exer.2018.04.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 04/05/2018] [Accepted: 04/09/2018] [Indexed: 12/20/2022]
Abstract
Our goal was to systematically quantify the collagen crimp morphology around the corneoscleral shell, and test the hypothesis that collagen crimp is not uniform over the globe. Axial longitudinal cryosections (30 μm) of three sheep eyes, fixed at 0 mmHg IOP, were imaged using polarized light microscopy to quantify the local collagen in 8 regions: two corneal (central and peripheral) and six scleral (limbus, anterior-equatorial, equatorial, posterior-equatorial, posterior and peripapillary). Collagen crimp period (length of one wave), tortuosity (path length divided by end-to-end length), waviness (SD of orientation), amplitude (half the peak to trough distance), and conformity (width of contiguous similarly oriented bundles) were measured in each region. Measurements were obtained on 8216 collagen fiber bundles. When pooling measurements across the whole eye globe, the median crimp values were: 23.9 μm period, 13.2 μm conformity, 0.63 μm amplitude, 1.006 tortuosity, and 12.7° waviness. However, all parameters varied significantly across the globe. Median bundle periods in the central cornea, limbus, and peripapillary sclera (PPS) were 14.1 μm, 29.5 μm, and 22.9 μm, respectively. Median conformities were 20.8 μm, 14.5 μm, and 15.1 μm, respectively. Median tortuosities were 1.005, 1.007, and 1.007, respectively. Median waviness' were 11.4°, 13.2°, and 13.2°, respectively. Median amplitudes were 0.35 μm, 0.87 μm, and 0.65 μm, respectively. All parameters varied significantly across the globe. All regions differed significantly from one another on at least one parameter. Regions with small periods had large conformities, and bundles with high tortuosity had high waviness and amplitude. Waviness, tortuosity, and amplitude, associated with nonlinear biomechanical behavior, exhibited "double hump" distributions, whereas period and conformity, representing tissue organization, were substantially different between sclera and cornea. Though the biomechanical implications and origin of the patterns observed remain unclear, our findings of well-defined patterns of collagen crimp across the corneoscleral shell, consistent between eyes, support the existence of mechanisms that regulate collagen characteristics at the regional or smaller levels. These results are experimental data necessary for more realistic models of ocular biomechanics and remodeling.
Collapse
Affiliation(s)
- Ning-Jiun Jan
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, USA; Department of Ophthalmology, University of Pittsburgh School of Medicine, USA
| | - Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh School of Medicine, USA
| | - Danielle Hu
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, USA; Department of Ophthalmology, University of Pittsburgh School of Medicine, USA
| | - Garrett Grube
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, USA
| | - Jacob Wallace
- Department of Ophthalmology, University of Pittsburgh School of Medicine, USA
| | - Alexandra Gogola
- Department of Ophthalmology, University of Pittsburgh School of Medicine, USA
| | - Ian A Sigal
- Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, USA; Department of Ophthalmology, University of Pittsburgh School of Medicine, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh, USA; The Louis J. Fox Center for Vision Restoration of UPMC and the University of Pittsburgh, Pittsburgh, PA, USA.
| |
Collapse
|