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Gluck MJ, Beck CM, Skodras A, Bernstein ZL, Rubin TA, Hausman MR, Cagle PJ. Second Harmonic Generation Microscopy as a Novel Intraoperative Assessment of Rat Median Nerve Injury. J Hand Surg Am 2023; 48:1170.e1-1170.e7. [PMID: 36357225 DOI: 10.1016/j.jhsa.2022.09.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/30/2022] [Accepted: 09/21/2022] [Indexed: 11/09/2022]
Abstract
PURPOSE Nerves that are functionally injured but appear macroscopically intact pose the biggest clinical dilemma. Second Harmonic Generation (SHG) Microscopy may provide a real-time assessment of nerve damage, with the ultimate goal of allowing surgeons to accurately quantify the degree of nerve damage present. The aim of this study was to demonstrate the utility of SHG microscopy to detect nerve damage in vivo in an animal model. METHODS Ten Sprague-Dawley rats were anesthetized and prepared for surgery. After surgical exposure and using a custom-made stretch applicator, the right median nerves were stretched by 20%, corresponding to a high strain injury, and held for 5 minutes. The left median nerve served as a sham control (SC), only being placed in the applicator for 5 minutes with no stretch. A nerve stimulator was used to assess the amount of stimulation required to induce a flicker and contraction of the paw. Nerves were then imaged using a multiphoton laser scanning microscope. RESULTS Immediately after injury (day 0), SHG images of SC median nerves exhibited parallel collagen fibers with linear, organized alignment. In comparison with SC nerves, high strain nerves demonstrated artifacts indicative of nerve damage consisting of wavy, undulating fibers with crossing fibers and tears, as well as a decrease in the linear organization, which correlated with an increase in the mean stimulation required to induce a flicker and contraction of the paw. CONCLUSIONS Second Harmonic Generation microscopy may provide the ability to detect an acute neural stretch injury in the rat median nerve. Epineurial collagen disorganization correlated with the stimulation required for nerve function. CLINICAL RELEVANCE In the future, SHG may provide the ability to visualize nerve damage intraoperatively, allowing for better clinical decision-making. However, this is currently a research tool and requires further validation before translating to the clinical setting.
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Affiliation(s)
- Matthew J Gluck
- Department of Orthopaedic Surgery, Mount Sinai Hospital, New York, NY; Icahn School of Medicine- Mount Sinai, New York, NY.
| | - Christina M Beck
- Division of Plastic Surgery, University of Washington, Seattle, WA
| | - Angelos Skodras
- Microscopy and Advanced Bioimaging Core, Icahn School of Medicine- Mount Sinai, New York, NY
| | | | - Todd A Rubin
- Hughston Clinic Orthopaedics at TriStar Centennial Medical Center, Nashville, TN
| | - Michael R Hausman
- Department of Orthopaedic Surgery, Mount Sinai Hospital, New York, NY; Icahn School of Medicine- Mount Sinai, New York, NY
| | - Paul J Cagle
- Department of Orthopaedic Surgery, Mount Sinai Hospital, New York, NY; Icahn School of Medicine- Mount Sinai, New York, NY
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Stocco E, Barbon S, Faccio D, Petrelli L, Incendi D, Zamuner A, De Rose E, Confalonieri M, Tolomei F, Todros S, Tiengo C, Macchi V, Dettin M, De Caro R, Porzionato A. Development and preclinical evaluation of bioactive nerve conduits for peripheral nerve regeneration: A comparative study. Mater Today Bio 2023; 22:100761. [PMID: 37600351 PMCID: PMC10433238 DOI: 10.1016/j.mtbio.2023.100761] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/24/2023] [Accepted: 08/04/2023] [Indexed: 08/22/2023] Open
Abstract
In severe peripheral nerve injuries, nerve conduits (NCs) are good alternatives to autografts/allografts; however, the results the available devices guarantee for are still not fully satisfactory. Herein, differently bioactivated NCs based on the new polymer oxidized polyvinyl alcohol (OxPVA) are compared in a rat model of sciatic nerve neurotmesis (gap: 5 mm; end point: 6 weeks). Thirty Sprague Dawley rats are randomized to 6 groups: Reverse Autograft (RA); Reaxon®; OxPVA; OxPVA + EAK (self-assembling peptide, mechanical incorporation); OxPVA + EAK-YIGSR (mechanical incorporation); OxPVA + Nerve Growth Factor (NGF) (adsorption). Preliminarily, all OxPVA-based devices are comparable with Reaxon® in Sciatic Functional Index score and gait analysis; moreover, all conduits sustain nerve regeneration (S100, β-tubulin) without showing substantial inflammation (CD3, F4/80) evidences. Following morphometric analyses, OxPVA confirms its potential in PNI repair (comparable with Reaxon®) whereas OxPVA + EAK-YIGSR stands out for its myelinated axons total number and density, revealing promising in injury recovery and for future application in clinical practice.
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Affiliation(s)
- Elena Stocco
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- Department of Cardiac, Thoracic and Vascular Science and Public Health, University of Padova, Via Nicolò Giustiniani 2, 35128, Padova, Italy
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Silvia Barbon
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Diego Faccio
- Plastic and Reconstructive Surgery Unit, University of Padova, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Lucia Petrelli
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
| | - Damiana Incendi
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
| | - Annj Zamuner
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
- Department of Civil, Environmental and Architectural Engineering University of Padova, Via Francesco Marzolo 9, 35131, Padova, Italy
- Department of Industrial Engineering University of Padova, Via Gradenigo 6/a, 35131, Padova, Italy
| | - Enrico De Rose
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
| | - Marta Confalonieri
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- Department of Industrial Engineering University of Padova, Via Gradenigo 6/a, 35131, Padova, Italy
| | - Francesco Tolomei
- Department of Industrial Engineering University of Padova, Via Gradenigo 6/a, 35131, Padova, Italy
| | - Silvia Todros
- Department of Industrial Engineering University of Padova, Via Gradenigo 6/a, 35131, Padova, Italy
| | - Cesare Tiengo
- Plastic and Reconstructive Surgery Unit, University of Padova, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Veronica Macchi
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Monica Dettin
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
- Department of Industrial Engineering University of Padova, Via Gradenigo 6/a, 35131, Padova, Italy
| | - Raffaele De Caro
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
| | - Andrea Porzionato
- Department of Neurosciences, Section of Human Anatomy, University of Padova, Via Aristide Gabelli 65, 35127, Padova, Italy
- L.i.f.e.L.a.b. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, Via Nicolò Giustiniani 2, 35128, Padova, Italy
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Rishøj L, Hernández IC, Ramachandran S, Jowett N. Multiphoton microscopy for label-free multicolor imaging of peripheral nerve. JOURNAL OF BIOMEDICAL OPTICS 2022; 27:JBO-210327GRR. [PMID: 35568795 PMCID: PMC9109936 DOI: 10.1117/1.jbo.27.5.056501] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 04/13/2022] [Indexed: 06/02/2023]
Abstract
SIGNIFICANCE Means for quantitation of myelinated fibers in peripheral nerve may guide diagnosis and clinical decision making in management of peripheral nerve disorders. Multiphoton microscopy techniques such as the third-harmonic generation enable label-free in vivo imaging of peripheral nerves. AIM Develop a multiphoton microscope based on a custom high-power infrared fiber laser for label-free imaging of peripheral nerve. APPROACH A cost-effective multiphoton microscope employing a single fiber laser source at 1300 nm was designed and used for stain-free multicolor imaging of murine and human peripheral nerve. RESULTS Second-harmonic generation signal from collagen centered about 650-nm delineated neural connective tissue, whereas third-harmonic general signal centered about 433-nm delineated myelin and other lipids. In sciatic nerve from transgenic reporter mice expressing yellow fluorescent protein within peripheral neurons, three-photon-excitation with emission peak at 527-nm delineated axoplasm. The signal obtained from unlabeled axially sectioned samples was adequate for segmentation of myelinated fibers using commercial image processing software. In unlabeled whole mount specimens, imaging depths over 100-μm were achieved. CONCLUSIONS A multiphoton microscope powered by a fiber laser enables stain-free histomorphometry of mammalian peripheral nerve. The simplicity of the microscope design carries potential for clinical translation to inform decision making in peripheral nerve disorders.
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Affiliation(s)
- Lars Rishøj
- Boston University, Department of Electrical and Computer Engineering, Boston, Massachusetts, United States
- Technical University of Denmark, DTU Fotonik, Kgs. Lyngby, Denmark
| | - Iván Coto Hernández
- Mass Eye and Ear and Harvard Medical School, Surgical Photonics and Engineering Laboratory, Boston, United States
| | - Siddharth Ramachandran
- Boston University, Department of Electrical and Computer Engineering, Boston, Massachusetts, United States
| | - Nate Jowett
- Mass Eye and Ear and Harvard Medical School, Surgical Photonics and Engineering Laboratory, Boston, United States
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Recovery and Regrowth After Nerve Repair: A Systematic Analysis of Four Repair Techniques. J Surg Res 2020; 251:311-320. [DOI: 10.1016/j.jss.2020.01.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 12/30/2019] [Accepted: 01/26/2020] [Indexed: 02/05/2023]
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Elyahoodayan S, Larson C, Cobo AM, Meng E, Song D. Acute in vivo testing of a polymer cuff electrode with integrated microfluidic channels for stimulation, recording, and drug delivery on rat sciatic nerve. J Neurosci Methods 2020; 336:108634. [PMID: 32068010 DOI: 10.1016/j.jneumeth.2020.108634] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/11/2020] [Accepted: 02/11/2020] [Indexed: 01/15/2023]
Abstract
BACKGROUND Extraneural cuffs are among the least invasive peripheral nerve interfaces as they remain outside the nerve. However, compared with more invasive interfaces, these electrodes may suffer from lower selectivity and sensitivity since the targeted nerve fibers are more distanced from the electrodes. NEW METHOD A lyse-and-attract cuff electrode (LACE) was enabled by microfabrication and developed to improve selectivity and sensitivity while maintaining a cuff format. Its engineering design was described in previous work. LACE is a hybrid cuff that integrates both microelectrodes and microfluidic channels. The ultimate goal is to increase fascicular selectivity and sensitivity by focal delivery via the microchannels of (1) lysing agent to remove connective tissue separating electrodes from nerve fibers, and (2) neurotrophic factors to promote axonal sprouting of the exposed nerve fibers into microfluidic channels where electrodes are embedded. Here, we focus on demonstrating in vivo function of microfluidics and microelectrodes in an acute preparation in which we evaluate the ability to focally remove connective tissue and record and stimulate with microchannel-embedded microelectrodes neural activity in rat sciatic nerves. COMPARISON WITH EXISTING METHODS While extraneural interfaces prioritize nerve health and intraneural interfaces prioritize functionality, LACE represents a new extraneural approach which could potentially excel at both aims. RESULTS Surgical implantation demonstrate preservation of LACE function following careful and minimal handling. In vivo electrical evaluation demonstrates the ability of microelectrodes placed within microfluidic channels to successfully stimulate and record compound action potentials from rat sciatic nerve. Furthermore, collagen-rich epineurium was focally removed following infusion of collagenase via microchannels and confirmed via microscopy. CONCLUSION The feasibility of using a cuff having integrated microelectrodes and microfluidics to stimulate, record, and deliver drug to focally lyse away the epineurium layer was demonstrated in acute experiments on rat sciatic nerve.
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Affiliation(s)
- Sahar Elyahoodayan
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
| | - Christopher Larson
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
| | - Angelica M Cobo
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
| | - Ellis Meng
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90089, USA.
| | - Dong Song
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; Neuroscience Graduate Program, University of Southern California, Los Angeles, CA, 90089, USA.
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Sung J, Sikora-Klak J, Adachi SY, Orozco E, Shah SB. Decoupled epineurial and axonal deformation in mouse median and ulnar nerves. Muscle Nerve 2019; 59:619-628. [PMID: 30697763 DOI: 10.1002/mus.26437] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 01/18/2019] [Accepted: 01/27/2019] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Peripheral nerves accommodate mechanical loads during joint movement. Hypothesized protective features include increased nerve compliance near joints and axonal undulation. How axons perceive nerve deformation is poorly understood. We tested whether nerves increase local axonal undulation in regions of high epineurial strain to protect nerve fibers from strain-induced damage. METHODS Regional epineurial strain was measured near the elbow in median and ulnar nerves of mice expressing axonal fluorescence before and after decompression. Regional axonal tortuosity was quantified under confocal microscopy. RESULTS Nerves showed higher epineurial strain just distal to the medial epicondyle; these differences were eliminated after decompression. Axonal tortuosity also varied regionally; however, unlike in the epineurium, it was greater in proximal regions. DISCUSSION In this study we have proposed a neuromechanical model whereby axons can unravel along their entire length due to looser mechanical coupling to the peri/epineurium. Our findings have major implications for understanding nerve biomechanics and dysfunction. Muscle Nerve 59:619-619, 2019.
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Affiliation(s)
- Jaemyoung Sung
- Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA
- Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, MC 0863, La Jolla, California 92093, USA
| | - Jakub Sikora-Klak
- Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, MC 0863, La Jolla, California 92093, USA
| | - Stephanie Y Adachi
- Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA
- Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, MC 0863, La Jolla, California 92093, USA
| | - Elisabeth Orozco
- Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, MC 0863, La Jolla, California 92093, USA
- Research Division, Veterans Affairs San Diego Healthcare System, San Diego, California, USA
| | - Sameer B Shah
- Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Drive, MC 0863, La Jolla, California 92093, USA
- Research Division, Veterans Affairs San Diego Healthcare System, San Diego, California, USA
- Department of Bioengineering, University of California, San Diego, La Jolla, California, USA
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Abstract
An important issue in tissue biomechanics is to decipher the relationship between the mechanical behavior at macroscopic scale and the organization of the collagen fiber network at microscopic scale. Here, we present a protocol to combine traction assays with multiphoton microscopy in ex vivo murine skin. This multiscale approach provides simultaneously the stress/stretch response of a skin biopsy and the collagen reorganization in the dermis by use of second harmonic generation (SHG) signals and appropriate image processing.
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Andarawis-Puri N, Flatow EL. Promoting effective tendon healing and remodeling. J Orthop Res 2018; 36:3115-3124. [PMID: 30175859 PMCID: PMC6608714 DOI: 10.1002/jor.24133] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/06/2018] [Indexed: 02/04/2023]
Abstract
Daily activities subject our tendons to accumulation of sub-rupture fatigue injury which can lead to tendon rupture. Consequently, tendinopathies account for over 30% of musculoskeletal consultations. We adopted a multidisciplinary approach to determine the role of the extracellular matrix (ECM) in the pathogenesis of tendinopathy and impaired healing of ruptured tendons. We have been investigating three main areas: (i) the pathogenesis of tendon degeneration; (ii) approaches to promoting remodeling of sub-rupture fatigue injuries; and the (iii) role of the ECM in promoting scarless tendon healing. In this Kappa Delta Young Investigator award paper, we describe the key discoveries made in each of our three research areas of focus. Briefly, we discovered that sub-rupture fatigue damage can accumulate from just one bout of fatigue loading. Furthermore, any attempt to repair the fatigue damage diminishes as the severity of induced damage increases. We have utilized exercise to develop animal models of exercise-led degeneration and exercise-led repair of sub-rupture fatigue damage injuries, wherein underlying mechanisms can be uncovered, thereby overcoming a major hurdle to development of therapeutics. Since damage accumulation ultimately leads to rupture that is characterized by formation of a mechanically inferior scar, we have used the MRL/MpJ mouse to evaluate the role of the systemic environment and the local tendon environment in driving regeneration to identify new therapeutic pathways to promote scarless healing. Our data suggests that the therapeutic potential of the MRL/MpJ provisional ECM should be further explored as it may harness biological and structural mechanisms to promote scarless healing. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3115-3124, 2018.
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Affiliation(s)
- Nelly Andarawis-Puri
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York
- Hospital for Special Surgery, New York, New York
| | - Evan L. Flatow
- Department of Orthopaedic Surgery, Mount Sinai West, New York, New York
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Gluck MJ, Vijayaraghavan S, Sinclair EB, Ashraf A, Hausman MR, Cagle PJ. Detecting structural and inflammatory response after in vivo stretch injury in the rat median nerve via second harmonic generation. J Neurosci Methods 2018; 303:68-80. [PMID: 29454014 DOI: 10.1016/j.jneumeth.2018.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Revised: 02/07/2018] [Accepted: 02/11/2018] [Indexed: 10/18/2022]
Abstract
BACKGROUND Second Harmonic Generation (SHG) microscopy is a promising method for visualizing the collagenous structure of peripheral nerves. Assessing collagen continuity and damage after a stretch injury provides inferential insight into the level of axonal damage present. NEW METHODS This study utilizes SHG microscopy after a calibrated in vivo stretch injury of rat median nerves to evaluate collagen continuity at several time points throughout the recovery process. Endoneurial collagen was qualitatively assessed in nerves that were subjected to low strain (LS) and high strain (HS) injuries using SHG microscopy, conventional histology, and immunohistochemistry. RESULTS Following an in vivo stretch injury, both LS and HS damaged nerves exhibit signs of structural collagen damage in comparison with sham control nerves (SC). Furthermore, LS nerves exhibit signs of full regeneration while HS nerves exhibited signs of only partial regeneration with lasting damage and intra-neural scar formation. COMPARISON WITH EXISTING METHODS SHG observations of structural changes and inflammatory response due to stretch injury were validated upon comparison with conventional histological methods CONCLUSIONS: We propose that SHG microscopy can be utilized to visualize significant structural artifacts in sectioned median nerves following in vivo stretch injury. Based on the findings in this study, we believe that the in vivo application of SHG microscopy should be further investigated as a means for real-time, intra-operative, quantitative assessment of nerve damage.
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Affiliation(s)
- Matthew J Gluck
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States.
| | - Surabhi Vijayaraghavan
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States
| | - Elaine B Sinclair
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States
| | - Asad Ashraf
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States
| | - Michael R Hausman
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States
| | - Paul J Cagle
- Leni & Peter W. May Department of Orthopaedic Surgery, Icahn School of Medicine at Mount Sinai, United States
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Quantification of Collagen Organization after Nerve Repair. PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN 2017; 5:e1586. [PMID: 29632766 PMCID: PMC5889458 DOI: 10.1097/gox.0000000000001586] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 10/13/2017] [Indexed: 01/09/2023]
Abstract
Background: Clinical outcomes after nerve injury and repair remain suboptimal. Patients may be plagued by poor functional recovery and painful neuroma at the repair site, characterized by disorganized collagen and sprouting axons. Collagen deposition during wound healing can be intrinsically imaged using second harmonic generation (SHG) microscopy. The purpose of this study was to develop a protocol for SHG imaging of nerves and to assess whether collagen alignment can be quantified after nerve repair. Methods: Sciatic nerve transection and epineural repair was performed in male rats. The contralateral nerves were used as intra-animal controls. Ten-millimeter nerve segments were harvested and fixed onto slides. SHG images were collected using a 20× objective on a multiphoton microscope. Collagen fiber alignment was calculated using CurveAlign software. Alignment was calculated on a scale from 0 to 1, where 1 represents perfect alignment. Statistical analysis was performed using a linear mixed-effects model. Results: Eight male rats underwent right sciatic nerve repair using 9-0 Nylon suture. There were gross variations in collagen fiber organization in the repaired nerves compared with the controls. Quantitatively, collagen fibers were more aligned in the control nerves (mean alignment 0.754, SE 0.055) than in the repairs (mean alignment 0.413, SE 0.047; P < 0.001). Conclusions: SHG microscopy can be used to quantitate collagen after nerve repair via fiber alignment. Given that the development of neuroma likely reflects aberrant wound healing, ex vivo and/or in vivo SHG imaging may be useful for further investigation of the variables predisposing to neuroma.
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How aging impacts skin biomechanics: a multiscale study in mice. Sci Rep 2017; 7:13750. [PMID: 29061975 PMCID: PMC5653787 DOI: 10.1038/s41598-017-13150-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 09/19/2017] [Indexed: 12/21/2022] Open
Abstract
Skin aging is a complex process that strongly affects the mechanical behavior of skin. This study aims at deciphering the relationship between age-related changes in dermis mechanical behavior and the underlying changes in dermis microstructure. To that end, we use multiphoton microscopy to monitor the reorganization of dermal collagen during mechanical traction assays in ex vivo skin from young and old mice. The simultaneous variations of a full set of mechanical and microstructural parameters are analyzed in the framework of a multiscale mechanical interpretation. They show consistent results for wild-type mice as well as for genetically-modified mice with modified collagen V synthesis. We mainly observe an increase of the tangent modulus and a lengthening of the heel region in old murine skin from all strains, which is attributed to two different origins that may act together: (i) increased cross-linking of collagen fibers and (ii) loss of water due to proteoglycans deterioration, which impedes inner sliding within these fibers. In contrast, the microstructure reorganization upon stretching shows no age-related difference, which can be attributed to opposite effects of the decrease of collagen content and of the increase of collagen cross-linking in old mice.
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12
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Two Levels of Waviness Are Necessary to Package the Highly Extensible Nerves in Rorqual Whales. Curr Biol 2017; 27:673-679. [DOI: 10.1016/j.cub.2017.01.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/30/2016] [Accepted: 01/04/2017] [Indexed: 11/20/2022]
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Lenoir H, Dagneaux L, Canovas F, Waitzenegger T, Pham TT, Chammas M. Nerve stress during reverse total shoulder arthroplasty: a cadaveric study. J Shoulder Elbow Surg 2017; 26:323-330. [PMID: 27697454 DOI: 10.1016/j.jse.2016.07.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 06/18/2016] [Accepted: 07/01/2016] [Indexed: 02/01/2023]
Abstract
BACKGROUND Neurologic lesions are relatively common after total shoulder arthroplasty. These injuries are mostly due to traction. We aimed to identify the arm manipulations and steps during reverse total shoulder arthroplasty (RTSA) that affect nerve stress. METHODS Stress was measured in 10 shoulders of 5 cadavers by use of a tensiometer on each nerve from the brachial plexus, with shoulders in different arm positions and during different surgical steps of RTSA. RESULTS When we studied shoulder position without prostheses, relative to the neutral position, internal rotation increased stress on the radial and axillary nerves and external rotation increased stress on the musculocutaneous, median, and ulnar nerves. Extension was correlated with increase in stress on all nerves. Abduction was correlated with increase in stress for the radial nerve. We identified 2 high-risk steps during RTSA: humeral exposition, particularly when the shoulder was in a position of more extension, and glenoid exposition. The thickness of polyethylene humeral cups used was associated with increased nerve stress in all but the ulnar nerve. CONCLUSION During humeral preparation, the surgeon must be careful to limit shoulder extension. Care must be taken during exposure of the glenoid. Extreme rotation and oversized implants should be avoided to minimize stretch-induced neuropathies.
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Affiliation(s)
- Hubert Lenoir
- Centre Ostéo-Articulaire des Cèdres, Echirolles, France.
| | - Louis Dagneaux
- Hip, Knee and Foot Surgery Unit, Centre Hospitalier Régional Universitaire Montpellier University Hospital, Montpellier, France
| | - François Canovas
- Hip, Knee and Foot Surgery Unit, Centre Hospitalier Régional Universitaire Montpellier University Hospital, Montpellier, France; Laboratory of Anatomy, Montpellier 1 University, Montpellier, France
| | | | - Thuy Trang Pham
- Toulouse-Purpan University Hospital Center, Toulouse, France
| | - Michel Chammas
- Hand and Upper Extremity Surgery Unit, Centre Hospitalier Régional Universitaire Montpellier University Hospital, Montpellier, France
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Bancelin S, Lynch B, Bonod-Bidaud C, Ducourthial G, Psilodimitrakopoulos S, Dokládal P, Allain JM, Schanne-Klein MC, Ruggiero F. Ex vivo multiscale quantitation of skin biomechanics in wild-type and genetically-modified mice using multiphoton microscopy. Sci Rep 2015; 5:17635. [PMID: 26631592 PMCID: PMC4668561 DOI: 10.1038/srep17635] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 11/02/2015] [Indexed: 02/02/2023] Open
Abstract
Soft connective tissues such as skin, tendon or cornea are made of about 90% of extracellular matrix proteins, fibrillar collagens being the major components. Decreased or aberrant collagen synthesis generally results in defective tissue mechanical properties as the classic form of Elhers-Danlos syndrome (cEDS). This connective tissue disorder is caused by mutations in collagen V genes and is mainly characterized by skin hyperextensibility. To investigate the relationship between the microstructure of normal and diseased skins and their macroscopic mechanical properties, we imaged and quantified the microstructure of dermis of ex vivo murine skin biopsies during uniaxial mechanical assay using multiphoton microscopy. We used two genetically-modified mouse lines for collagen V: a mouse model for cEDS harboring a Col5a2 deletion (a.k.a. pN allele) and the transgenic K14-COL5A1 mice which overexpress the human COL5A1 gene in skin. We showed that in normal skin, the collagen fibers continuously align with stretch, generating the observed increase in mechanical stress. Moreover, dermis from both transgenic lines exhibited altered collagen reorganization upon traction, which could be linked to microstructural modifications. These findings show that our multiscale approach provides new crucial information on the biomechanics of dermis that can be extended to all collagen-rich soft tissues.
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Affiliation(s)
- Stéphane Bancelin
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM U1182, 91128 Palaiseau Cedex, FRANCE
| | - Barbara Lynch
- Solids Mechanics Laboratory Ecole Polytechnique, CNRS, Mines ParisTech, 91128 Palaiseau Cedex, FRANCE
| | - Christelle Bonod-Bidaud
- Institut de Génomique Fonctionnelle de Lyon, ENS-Lyon, CNRS UMR 5242, Université Lyon 1, 46 Allée d'Italie, 69364 Lyon, cedex 07 France
| | - Guillaume Ducourthial
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM U1182, 91128 Palaiseau Cedex, FRANCE
| | | | - Petr Dokládal
- Centre for Mathematical Morphology, MINES ParisTech, PSL Research University, 35 rue St Honoré, 77300 Fontainebleau, France
| | - Jean-Marc Allain
- Solids Mechanics Laboratory Ecole Polytechnique, CNRS, Mines ParisTech, 91128 Palaiseau Cedex, FRANCE
| | - Marie-Claire Schanne-Klein
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM U1182, 91128 Palaiseau Cedex, FRANCE
| | - Florence Ruggiero
- Institut de Génomique Fonctionnelle de Lyon, ENS-Lyon, CNRS UMR 5242, Université Lyon 1, 46 Allée d'Italie, 69364 Lyon, cedex 07 France
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15
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Lauria G, Dacci P, Lombardi R, Cazzato D, Porretta-Serapiglia C, Taiana M, Sassone J, Dalla Bella E, Rinaldo S, Lettieri C, Eleopra R, Devigili G. Side and time variability of intraepidermal nerve fiber density. Neurology 2015; 84:2368-71. [DOI: 10.1212/wnl.0000000000001666] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 02/26/2015] [Indexed: 11/15/2022] Open
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16
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Collagen Fibrils in Skin Orient in the Direction of Applied Uniaxial Load in Proportion to Stress while Exhibiting Differential Strains around Hair Follicles. MATERIALS 2015; 8:1841-1857. [PMID: 28788035 PMCID: PMC5507025 DOI: 10.3390/ma8041841] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 04/09/2015] [Accepted: 04/14/2015] [Indexed: 11/17/2022]
Abstract
We determined inhomogeneity of strains around discontinuities as well as changes in orientation of collagen fibrils under applied load in skin. Second Harmonic Generation (SHG) images of collagen fibrils were obtained at different strain magnitudes. Changes in collagen orientation were analyzed using Fast Fourier Transforms (FFT) while strain inhomogeneity was determined at different distances from hair follicles using Digital Image Correlation (DIC). A parameter, defined as the Collagen Orientation Index (COI), is introduced that accounts for the increasingly ellipsoidal nature of the FFT amplitude images upon loading. We show that the COI demonstrates two distinct mechanical regimes, one at low strains (0%, 2.5%, 5% strain) in which randomly oriented collagen fibrils align in the direction of applied deformation. In the second regime, beginning at 5% strain, collagen fibrils elongate in response to applied deformation. Furthermore, the COI is also found to be linearly correlated with the applied stress indicating that collagen fibrils orient to take the applied load. DIC results indicated that major principal strains were found to increase with increased load at all locations. In contrast, minimum principal strain was dependent on distance from hair follicles. These findings are significant because global and local changes in collagen deformations are expected to be changed by disease, and could affect stem cell populations surrounding hair follicles, including mesenchymal stem cells within the outer root sheath.
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