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Jeong EY, Kim HJ, Lee S, Park Y, Kim YM. Label-free long-term measurements of adipocyte differentiation from patient-driven fibroblasts and quantitative analyses of in situ lipid droplet generation. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2024; 41:C125-C136. [PMID: 39889084 DOI: 10.1364/josaa.528703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Accepted: 09/20/2024] [Indexed: 02/02/2025]
Abstract
The visualization and tracking of adipocytes and their lipid droplets (LDs) during differentiation are pivotal in developmental biology and regenerative medicine studies. Traditional staining or labeling methods, however, pose significant challenges due to their labor-intensive sample preparation, potential disruption of intrinsic cellular physiology, and limited observation timeframe. This study introduces a novel method for long-term visualization and quantification of biophysical parameters of LDs in unlabeled adipocytes, utilizing the refractive index (RI) distributions of LDs and cells. We employ low-coherence holotomography (HT) to systematically investigate and quantitatively analyze the 42-day redifferentiation process of fat cells into adipocytes. This technique yields three-dimensional, high-resolution refractive tomograms of adipocytes, enabling precise segmentation of LDs based on their elevated RI values. Subsequent automated analysis quantifies the mean concentration, volume, projected area, and dry mass of individual LDs, revealing a gradual increase corresponding with adipocyte maturation. Our findings demonstrate that HT is a potent tool for non-invasively monitoring live adipocyte differentiation and analyzing LD accumulation. This study, therefore, offers valuable insights into adipogenesis and lipid research, establishing HT and image-based analysis as a promising approach in these fields.
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Li J, Yan P, Li Y, Han M, Zeng Q, Li J, Yu Z, Zhang D, Chen X. Harnessing the power of Raman spectroscopic imaging for ophthalmology. Front Chem 2023; 11:1211121. [PMID: 37252371 PMCID: PMC10213270 DOI: 10.3389/fchem.2023.1211121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 05/04/2023] [Indexed: 05/31/2023] Open
Abstract
Eye diseases can cause great inconvenience to people's daily life; therefore, it is necessary to study the causes of ocular diseases and related physiological processes. Raman spectroscopic imaging (RSI) is a non-destructive, non-contact detection technique with the advantages of label-free, non-invasive and highly specific. Compared with other mature imaging technologies, RSI can provide real-time molecular information and high-resolution imaging at relatively low cost, making it very suitable for quantitative detection of biological molecules. RSI can reflect the overall situation of the sample, revealing the content distribution of the same substance in different areas of the sample. This review focuses on the recent advances in ophthalmology, with particular emphasis on the powerful use of RSI techniques, as well as its combination with other imaging techniques. Finally, we prospect the wider application and future potential of RSI approaches in ophthalmology.
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Affiliation(s)
- Jing Li
- Shaanxi Eye Hospital, Xi’an People’s Hospital (Xi’an Fourth Hospital), Affiliated People’s Hospital of Northwest University, Xi’an, Shaanxi, China
| | - Peirao Yan
- Center for Biomedical-photonics and Molecular Imaging, Xi’an Key Laboratory of Intelligent Sensing and Regulation of Trans-Scale Life Information, School of Life Science and Technology, Xidian University, Xi’an, Shaanxi, China
| | - Yong Li
- Shaanxi Eye Hospital, Xi’an People’s Hospital (Xi’an Fourth Hospital), Affiliated People’s Hospital of Northwest University, Xi’an, Shaanxi, China
| | - Ming Han
- Center for Biomedical-photonics and Molecular Imaging, Xi’an Key Laboratory of Intelligent Sensing and Regulation of Trans-Scale Life Information, School of Life Science and Technology, Xidian University, Xi’an, Shaanxi, China
| | - Qi Zeng
- Center for Biomedical-photonics and Molecular Imaging, Xi’an Key Laboratory of Intelligent Sensing and Regulation of Trans-Scale Life Information, School of Life Science and Technology, Xidian University, Xi’an, Shaanxi, China
| | - Juan Li
- Shaanxi Eye Hospital, Xi’an People’s Hospital (Xi’an Fourth Hospital), Affiliated People’s Hospital of Northwest University, Xi’an, Shaanxi, China
| | - Zhe Yu
- Shaanxi Eye Hospital, Xi’an People’s Hospital (Xi’an Fourth Hospital), Affiliated People’s Hospital of Northwest University, Xi’an, Shaanxi, China
| | - Dongjie Zhang
- Center for Biomedical-photonics and Molecular Imaging, Xi’an Key Laboratory of Intelligent Sensing and Regulation of Trans-Scale Life Information, School of Life Science and Technology, Xidian University, Xi’an, Shaanxi, China
| | - Xueli Chen
- Center for Biomedical-photonics and Molecular Imaging, Xi’an Key Laboratory of Intelligent Sensing and Regulation of Trans-Scale Life Information, School of Life Science and Technology, Xidian University, Xi’an, Shaanxi, China
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Tabish TA, Narayan RJ, Edirisinghe M. Rapid and label-free detection of COVID-19 using coherent anti-Stokes Raman scattering microscopy. MRS COMMUNICATIONS 2020; 10:566-572. [PMID: 33398237 PMCID: PMC7773019 DOI: 10.1557/mrc.2020.81] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 10/26/2020] [Indexed: 05/18/2023]
Abstract
From the 1918 influenza pandemic (H1N1) until the recent 2019 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, no efficient diagnostic tools have been developed for sensitive identification of viral pathogens. Rigorous, early, and accurate detection of viral pathogens is not only linked to preventing transmission but also to timely treatment and monitoring of drug resistance. Reverse transcription-polymerase chain reaction (RT-PCR), the gold standard method for microbiology and virology testing, suffers from both false-negative and false-positive results arising from the detection limit, contamination of samples/templates, exponential DNA amplification, and variation of viral ribonucleic acid sequences within a single individual during the course of the infection. Rapid, sensitive, and label-free detection of SARS-CoV-2 can provide a first line of defense against the current pandemic. A promising technique is non-linear coherent anti-Stokes Raman scattering (CARS) microscopy, which has the ability to capture rich spatiotemporal structural and functional information at a high acquisition speed in a label-free manner from a biological system. Raman scattering is a process in which the distinctive spectral signatures associated with light-sample interaction provide information on the chemical composition of the sample. In this prospective, we briefly discuss the development and future prospects of CARS for real-time multiplexed label-free detection of SARS-CoV-2 pathogens.
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Affiliation(s)
- Tanveer A. Tabish
- UCL Cancer Institute, University College London, London, Bloomsbury, WC1E 6DD UK
| | - Roger J. Narayan
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC 27599-7115 USA
| | - Mohan Edirisinghe
- Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE UK
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Howlett ID, Han W, Gordon M, Rice P, Barton JK, Kostuk RK. Volume holographic imaging endoscopic design and construction techniques. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:56010. [PMID: 28564690 PMCID: PMC5449719 DOI: 10.1117/1.jbo.22.5.056010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/11/2017] [Indexed: 05/04/2023]
Abstract
A reflectance volume holographic imaging (VHI) endoscope has been designed for simultaneous in vivo imaging of surface and subsurface tissue structures. Prior utilization of VHI systems has been limited to ex vivo tissue imaging. The VHI system presented in this work is designed for laparoscopic use. It consists of a probe section that relays light from the tissue sample to a handheld unit that contains the VHI microscope. The probe section is constructed from gradient index (GRIN) lenses that form a 1:1 relay for image collection. The probe has an outer diameter of 3.8 mm and is capable of achieving 228.1 ?? lp / mm resolution with 660-nm Kohler illumination. The handheld optical section operates with a magnification of 13.9 and a field of view of 390 ?? ? m × 244 ?? ? m . System performance is assessed through imaging of 1951 USAF resolution targets and soft tissue samples. The system has also passed sterilization procedures required for surgical use and has been used in two laparoscopic surgical procedures.
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Affiliation(s)
- Isela D. Howlett
- University of Arizona, College of Optical Sciences, Tucson, Arizona, United States
- University of Arizona, Department of Electrical and Computer Engineering, Tucson, Arizona, United States
- Address all correspondence to: Isela D. Howlett, E-mail:
| | - Wanglei Han
- University of Arizona, College of Optical Sciences, Tucson, Arizona, United States
- University of Arizona, Department of Electrical and Computer Engineering, Tucson, Arizona, United States
| | - Michael Gordon
- University of Arizona, College of Optical Sciences, Tucson, Arizona, United States
- University of Arizona, Department of Electrical and Computer Engineering, Tucson, Arizona, United States
| | - Photini Rice
- University of Arizona, Biomedical Engineering Department, Tucson, Arizona, United States
| | - Jennifer K. Barton
- University of Arizona, College of Optical Sciences, Tucson, Arizona, United States
- University of Arizona, Department of Electrical and Computer Engineering, Tucson, Arizona, United States
- University of Arizona, Biomedical Engineering Department, Tucson, Arizona, United States
| | - Raymond K. Kostuk
- University of Arizona, College of Optical Sciences, Tucson, Arizona, United States
- University of Arizona, Department of Electrical and Computer Engineering, Tucson, Arizona, United States
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Murashova GA, Mancuso CA, Sakami S, Palczewski K, Palczewska G, Dantus M. Epi-direction detected multimodal imaging of an unstained mouse retina with a Yb-fiber laser. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2017; 10069:100692K. [PMID: 28989217 PMCID: PMC5627661 DOI: 10.1117/12.2252457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this work, we present all epi-direction detected images of an unstained mouse retina using multiphoton microscopy with a sub-50 fs Yb-fiber laser centered at 1.07 μm. This wavelength is particularly interesting as the fundamental wavelength is transparent to the anterior segment of the eye and the higher harmonics are above DNA-damaging UV wavelengths. We present a characterization of the multimodal signals emitted from the different retinal layers, as well as from the choroid and the sclera. By characterizing native multiphoton signals from the retina, we move closer to having Yb-fiber considered for in vivo diagnosis of retinal disease through multiphoton microscopy as well as for corrective therapies.
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Affiliation(s)
| | | | - Sanae Sakami
- Department of Pharmacology, Case Western Reserve University, Cleveland OH 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University, Cleveland OH 44106, USA
| | | | - Marcos Dantus
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA
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Zhang J, Ren L, Mei X, Xu Q, Zheng W, Liu Z. Microstructure visualization of conventional outflow pathway and finite element modeling analysis of trabecular meshwork. Biomed Eng Online 2016; 15:162. [PMID: 28155681 PMCID: PMC5259963 DOI: 10.1186/s12938-016-0254-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The intraocular pressure (IOP) is maintained through a dynamic equilibrium between the production and drainage of aqueous humor. Elevation of intraocular pressure is mainly caused by the blocking of aqueous humor outflow pathway. Therefore, it is particularly important to study the structure of drainage pathway and the effect of ocular hypertension at the process of aqueous humor outflow. METHODS Conventional drainage pathway of aqueous humor, including trabecular meshwork (TM), Schlemm's canal (SC) and aqueous vein, were imaged by using trans-scleral imaging method with lateral resolution of 2 μm. For quantitative assessment, the morphological parameters of the TM were measured with different IOP levels via a combination of measurements and simulations. RESULTS Images of the TM and the adjacent tissues were obtained. The porosity of TM with normal intraocular pressure varies from 0.63 to 0.74 as the depth increases, while in high IOP it is changed from 0.44 to 0.59. The diameter of aqueous vein varies from 32 to 43 μm, and is smaller than that of SC, which varies from 48 to 64.67 μm. CONCLUSIONS Our research provides a non-contact method to visualize the microstructure of tissue for clinical examination associated with the blocking of the outflow pathway of aqueous humor in humans. The three-dimensional (3D) microstructures of limbus and the results of finite element modeling analysis of the TM model will serve for the future evaluation of new glaucoma surgical techniques.
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Affiliation(s)
- Jing Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China
| | - Lin Ren
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China
| | - Xi Mei
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China.,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China
| | - Qiang Xu
- Shenzhen Key Lab for Molecular Imaging, Research Lab for Biomedical Optics and Molecular Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Wei Zheng
- Shenzhen Key Lab for Molecular Imaging, Research Lab for Biomedical Optics and Molecular Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
| | - Zhicheng Liu
- School of Biomedical Engineering, Capital Medical University, Beijing, 100069, China. .,Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing, 100069, China.
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Abstract
Clinical diagnostic devices provide new sources of information that give insight about the state of health which can then be used to manage patient care. These tools can be as simple as an otoscope to better visualize the ear canal or as complex as a wireless capsule endoscope to monitor the gastrointestinal tract. It is with tools such as these that medical practitioners can determine when a patient is healthy and to make an appropriate diagnosis when he/she is not. The goal of diagnostic medicine then is to efficiently determine the presence and cause of disease in order to provide the most appropriate intervention. The earliest form of medical diagnostics relied on the eye - direct visual observation of the interaction of light with the sample. This technique was espoused by Hippocrates in his 5th century BCE work Epidemics, in which the pallor of a patient's skin and the coloring of the bodily fluids could be indicative of health. In the last hundred years, medical diagnosis has moved from relying on visual inspection to relying on numerous technological tools that are based on various types of interaction of the sample with different types of energy - light, ultrasound, radio waves, X-rays etc. Modern advances in science and technology have depended on enhancing technologies for the detection of these interactions for improved visualization of human health. Optical methods have been focused on providing this information in the micron to millimeter scale while ultrasound, X-ray, and radio waves have been key in aiding in the millimeter to centimeter scale. While a few optical technologies have achieved the status of medical instruments, many remain in the research and development phase despite persistent efforts by many researchers in the translation of these methods for clinical care. Of these, Raman spectroscopy has been described as a sensitive method that can provide biochemical information about tissue state while maintaining the capability of delivering this information in real-time, non-invasively, and in an automated manner. This review presents the various instrumentation considerations relevant to the clinical implementation of Raman spectroscopy and reviews a subset of interesting applications that have successfully demonstrated the efficacy of this technique for clinical diagnostics and monitoring in large (n ≥ 50) in vivo human studies.
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Affiliation(s)
- Isaac Pence
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
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Abstract
Advancements in coherent Raman scattering (CRS) microscopy have enabled label-free visualization and analysis of functional, endogenous biomolecules in living systems. When compared with spontaneous Raman microscopy, a key advantage of CRS microscopy is the dramatic improvement in imaging speed, which gives rise to real-time vibrational imaging of live biological samples. Using molecular vibrational signatures, recently developed hyperspectral CRS microscopy has improved the readout of chemical information available from CRS images. In this article, we review recent achievements in CRS microscopy, focusing on the theory of the CRS signal-to-noise ratio, imaging speed, technical developments, and applications of CRS imaging in bioscience and clinical settings. In addition, we present possible future directions that the use of this technology may take.
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Affiliation(s)
- Chi Zhang
- Weldon School of Biomedical Engineering and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;
| | - Delong Zhang
- Weldon School of Biomedical Engineering and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;
| | - Ji-Xin Cheng
- Weldon School of Biomedical Engineering and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;
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Direct label-free measurement of the distribution of small molecular weight compound inside thick biological tissue using coherent Raman microspectroscopy. Sci Rep 2015; 5:13868. [PMID: 26353981 PMCID: PMC4564726 DOI: 10.1038/srep13868] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 08/07/2015] [Indexed: 02/01/2023] Open
Abstract
Distributions of small molecular weight (less than 300 Da) compounds inside biological tissue have been obscure because of the lack of appropriate methods to measure them. Although fluorescence techniques are widely used to characterise the localisation of large biomolecules, they cannot be easily applied to the cases with small molecule compounds. We used CARS spectroscopy to detect and identify a label-free small molecule compound. To facilitate detection in aqueous environment, we utilised time-resolved and phase-sensitive techniques to reduce non-resonant background generated from water. We applied this technique to detect small molecular weight compound, taurine, inside mouse cornea tissue immersed in taurine solution as an initial model experiment. We detected a Raman peak of taurine near wavenumber 1033 cm−1 inside cornea and successfully characterised its depth profile in the tissue. Our CARS spectra measurement can be a promising method to measure and visualise the distribution of small bio-related compounds in biological background without using any labeling, paving the way for new cell biological analysis in various disciplines.
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Masihzadeh O, Lei TC, Domingue SR, Kahook MY, Bartels RA, Ammar DA. Third harmonic generation microscopy of a mouse retina. Mol Vis 2015; 21:538-47. [PMID: 25999681 PMCID: PMC4440497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/30/2015] [Indexed: 12/02/2022] Open
Abstract
PURPOSE To demonstrate lipid-specific imaging of the retina through the use of third harmonic generation (THG), a multiphoton microscopic technique in which tissue contrast is generated from optical inhomogeneities. METHODS A custom fiber laser and multiphoton microscope was constructed and optimized for simultaneous two-photon autofluorescence (TPAF) and THG retinal imaging. Imaging was performed using fixed-frozen sections of mouse eyes without the use of exogenous fluorescent dyes. In parallel experiments, a fluorescent nuclear stain was used to verify the location of the retinal cell nuclei. RESULTS Simultaneous THG and TPAF images revealed all retinal layers with subcellular resolution. In BALB/c strains, the THG signal stems from the lipidic organelles of the cellular and nuclear membranes. In the C57BL/6 strain, the THG signal from the RPE cells originates from the pigmented granules. CONCLUSIONS THG microscopy can be used to image structures of the mouse retina using contrast inherent to the tissue and without the use of a fluorescent dye or exogenously expressed recombinant protein.
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Affiliation(s)
- Omid Masihzadeh
- Department of Ophthalmology, University of Colorado Denver, Aurora, CO
| | - Tim C. Lei
- Department of Electrical Engineering, University of Colorado Denver, Denver, CO
| | - Scott R. Domingue
- Department of Electrical Engineering, Colorado State University, Fort Collins, CO
| | - Malik Y. Kahook
- Department of Ophthalmology, University of Colorado Denver, Aurora, CO
| | - Randy A. Bartels
- Department of Electrical Engineering, Colorado State University, Fort Collins, CO
| | - David A. Ammar
- Department of Ophthalmology, University of Colorado Denver, Aurora, CO
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Lei TC, Masihzadeh O, Kahook MY, Ammar DA. Imaging the effects of prostaglandin analogues on cultured trabecular meshwork cells by coherent anti-stokes Raman scattering. Invest Ophthalmol Vis Sci 2013; 54:5972-80. [PMID: 23900606 DOI: 10.1167/iovs.13-12065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The aim of this study was to nondestructively monitor morphological changes to the lipid membranes of primary cultures of living human trabecular meshwork cells (hTMC) without the application of exogenous label. METHODS Live hTMC were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). The hTMC were treated with a commercial formulation of latanoprost (0.5 μg/mL) for 24 hours before imaging. Untreated cells and cells treated with vehicle containing the preservative benzalkonium chloride (BAK; 2 μg/mL) were imaged as controls. After CARS/TPAF imaging, hTMC were fixed, stained with the fluorescent lipid dye Nile Red, and imaged by conventional confocal microscopy to verify lipid membrane structures. RESULTS Analysis of CARS/TPAF images of hTMC treated with latanoprost revealed multiple intracellular lipid membranes absent from untreated or BAK-treated hTMC. Treatment of hTMC with sodium fluoride or ouabain, agents shown to cause morphological changes to hTMC, also did not induce formation of intracellular lipid membranes. CONCLUSIONS CARS microscopy detected changes in living hTMC morphology that were validated by subsequent histological stain. Prostaglandin-induced changes to hTMC involved rearrangement of lipid membranes within these cells. These in vitro results identify a novel biological response to a class of antiglaucoma drugs, and further experiments are needed to establish how this effect is involved in the hypotensive action of prostaglandin analogues in vivo.
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Affiliation(s)
- Tim C Lei
- Department of Electrical Engineering, University of Colorado Denver, Denver, Colorado, USA
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Ammar DA, Lei TC, Kahook MY, Masihzadeh O. Imaging the intact mouse cornea using coherent anti-stokes Raman scattering (CARS). Invest Ophthalmol Vis Sci 2013; 54:5258-65. [PMID: 23821187 DOI: 10.1167/iovs.12-11513] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE The aim of this study was to image the cellular and noncellular structures of the cornea and limbus in an intact mouse eye using the vibrational oscillation of the carbon-hydrogen bond in lipid membranes and autofluorescence as label-free contrast agents. METHODS Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Sequential images were collected through the full thickness of the cornea and limbal regions. Line scans along the transverse/sagittal axes were also performed. RESULTS Analysis of multiple CARS/TPAF images revealed that corneal epithelial and endothelial cells could be identified by the lipid-rich plasma membrane CARS signal. The fluorescent signal from the collagen fibers of the corneal stroma was evident in the TPAF channel. The transition from the cornea to sclera at the limbus was marked by a change in collagen pattern (TPAF channel) and thickness of surface cells (CARS channel). Regions within the corneal stroma that lack collagen autofluorescence coincided with CARS signal, indicating the presence of stromal fibroblasts or nerve fibers. CONCLUSIONS The CARS technique was successful in imaging cells in the intact mouse eye, both at the surface and within corneal tissue. Multiphoton images were comparable to histologic sections. The methods described here represent a new avenue for molecular specific imaging of the mouse eye. The lack of need for tissue fixation is unique compared with traditional histology imaging techniques.
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Affiliation(s)
- David A Ammar
- Department of Ophthalmology, University of Colorado Denver, Aurora, Colorado 80045, USA
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