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Mizuno M, Maeda Y, Sanami S, Matsuzaki T, Yoshikawa HY, Ozeki N, Koga H, Sekiya I. Noninvasive total counting of cultured cells using a home-use scanner with a pattern sheet. iScience 2024; 27:109170. [PMID: 38405610 PMCID: PMC10884908 DOI: 10.1016/j.isci.2024.109170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 11/07/2023] [Accepted: 02/06/2024] [Indexed: 02/27/2024] Open
Abstract
The inherent variability in cell culture techniques hinders their reproducibility. To address this issue, we introduce a comprehensive cell observation device. This new approach enhances the features of existing home-use scanners by implementing a pattern sheet. Compared with fluorescent staining, our method over- or underestimated the cell count by a mere 5%. The proposed technique showcased a strong correlation with conventional methodologies, displaying R2 values of 0.91 and 0.99 compared with the standard chamber and fluorescence methods, respectively. Simulations of microscopic observations indicated the potential to estimate accurately the total cell count using just 20 fields of view. Our proposed cell-counting device offers a straightforward, noninvasive means of measuring the number of cultured cells. By harnessing the power of deep learning, this device ensures data integrity, thereby making it an attractive option for future cell culture research.
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Affiliation(s)
- Mitsuru Mizuno
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University (TMDU), 1-5-45, Bunkyo-ku, Yushima, Tokyo 113-8519, Japan
| | - Yoshitaka Maeda
- Medical & Healthcare Division, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Sho Sanami
- Medical & Healthcare Division, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Takahisa Matsuzaki
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita City, Osaka 565-0871, Japan
| | - Hiroshi Y. Yoshikawa
- Department of Applied Physics, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita City, Osaka 565-0871, Japan
| | - Nobutake Ozeki
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University (TMDU), 1-5-45, Bunkyo-ku, Yushima, Tokyo 113-8519, Japan
| | - Hideyuki Koga
- Department of Joint Surgery and Sports Medicine, Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Ichiro Sekiya
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University (TMDU), 1-5-45, Bunkyo-ku, Yushima, Tokyo 113-8519, Japan
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Watanabe H, Sanami S, Kitasaka H, Tsuzuki Y, Kida Y, Takeda S, Kondo F, Takeda S, Fukunaga N, Asada Y. IMPROVEMENT OF AN AUTOMATIC PRONUCLEAR NUMBER DETECTION SYSTEM BY INTRODUCTION OF NEW ANALYTICAL METHODS. Fertil Steril 2021. [DOI: 10.1016/j.fertnstert.2021.07.417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Kondo F, Fukunaga N, Sanami S, Kitasaka H, Tsuzuki Y, Kida Y, Takeda S, Watanabe H, Takeda S, Asada Y. CYTOPLASMIC MORPHOLOGICAL CHARACTERISTICSAFFECT 2PN DETECTION IN AN AUTOMATIC PRONUCLEAR NUMBER DETECTION SYSTEM USING DEEP LEARNING TECHNOLOGY. Fertil Steril 2021. [DOI: 10.1016/j.fertnstert.2021.07.434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Takeda S, Fukunaga N, Sanami S, Tsuzuki Y, Kitasaka H, Takeda S, Watanabe H, Kida Y, Kondou F, Asada Y. P–156 Automatic pronuclear detection based on deep learning technology has clinical utility. Hum Reprod 2021. [DOI: 10.1093/humrep/deab130.155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Study question
Does the performance of an automatic pronuclear detection system based on deep learning technology have clinical utility?
Summary answer
Output results for 2PN detection using the automatic system powered by deep learning technology has clinical utility.
What is known already
In order to establish a more objective embryo evaluation system, we have been developing an automatic pronuclear detection system that utilizes deep learning technology based on Time- Lapse (TL) images. We have previously reported that the accuracy of pronuclei detection was improved by introducing an analysis method using 11 slices in the Z axis. In this study, we evaluated the potential clinical practicality of the automatic pronuclear detection system.
Study design, size, duration
Embryos clinically evaluated between May 2018 and December 2019 by embryologists were chosen for this study. We prepared for analysis TL videos of 995 embryos that had been evaluated as having 0, 1, 2, and 3PN.
Participants/materials, setting, methods
Part1:We compared the outputs of the automatic pronuclear detection system with these embryologists(three junior embryologists (1a), three intermediate embryologists (1b),and three senior embryologists (1c)) who had judged the pronuclei number from TL videos from 40 embryos each having 0,1,2,and 3PN.
Part2:The automatic pronuclear detection system determined the pronuclei number from the TL videos of 955 embryos scored as either 1,2,and 3PN,(different from those used in Part1),and the detection rate for 2PN was calculated.
Main results and the role of chance
Part1: The sensitivities for embryologist groups 1a),1b),1c) and the automatic pronuclear detection system were 80.0%,100%,100%,100% for 2PN, 60.0%,83.3%,86.7%,100% for 0PN, 46.7%,80.0%,86.7%,10.0% for 1PN, and 73.3%,96.7%,96.7%,10.0% for 3PN.
Part2: The precision for 2PN by the automatic pronuclear detection system was 99%.
Limitations, reasons for caution
In order to further improve the performance of the automatic pronuclear detection system, further adjustment of the algorithm and more training images will be utilised.
Wider implications of the findings: The detection of 2PN by the automatic pronuclear detection system was highly reliable, and the performance of the system was comparable to that of embryologists. These first results are reassuring and support the clinical use of the system as a further aid for embryologists, in routine laboratory practice.
Trial registration number
‘not applicable’
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Affiliation(s)
- S Takeda
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - N Fukunaga
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - S Sanami
- Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Y Tsuzuki
- Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - H Kitasaka
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - S Takeda
- Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - H Watanabe
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - Y Kida
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - F Kondou
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
| | - Y Asada
- Asada Ladies Clinic, Asada Institute for Reproductive Medicine, Aichi, Japan
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Iseoka H, Sasai M, Miyagawa S, Takekita K, Date S, Ayame H, Nishida A, Sanami S, Hayakawa T, Sawa Y. Rapid and sensitive mycoplasma detection system using image-based deep learning. J Artif Organs 2021; 25:50-58. [PMID: 34160717 PMCID: PMC8866286 DOI: 10.1007/s10047-021-01282-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Accepted: 06/02/2021] [Indexed: 11/27/2022]
Abstract
A major concern in the clinical application of cell therapy is the manufacturing cost of cell products, which mainly depends on quality control. The mycoplasma test, an important biological test in cell therapy, takes several weeks to detect a microorganism and is extremely expensive. Furthermore, the manual detection of mycoplasma from images requires high-level expertise. We hypothesized that a mycoplasma identification program using a convolutional neural network could reduce the test time and improve sensitivity. To this end, we developed a program comprising three parts (mycoplasma detection, prediction, and cell counting) that allows users to evaluate the sample and verify infected/non-infected cells identified by the program. In experiments conducted, stained DNA images of positive and negative control using mycoplasma-infected and non-infected Vero cells, respectively, were used as training data, and the program results were compared with those of conventional methods, such as manual counting based on visual observation. The minimum detectable mycoplasma contaminations for manual counting and the proposed program were 10 and 5 CFU (colony-forming unit), respectively, and the test time for manual counting was 20 times that for the proposed program. These results suggest that the proposed system can realize a low-cost and streamlined manufacturing process for cellular products in cell-based research and clinical applications.
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Affiliation(s)
- Hiroko Iseoka
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
| | - Masao Sasai
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
| | - Shigeru Miyagawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
| | - Kazuhiro Takekita
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
| | - Satoshi Date
- Dai Nippon Printing Co., Ltd., Shinjuku, Tokyo Japan
| | | | - Azusa Nishida
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
| | - Sho Sanami
- Dai Nippon Printing Co., Ltd., Shinjuku, Tokyo Japan
| | - Takao Hayakawa
- Osaka University Faculty of Medicine, Suita-city, Osaka Japan
| | - Yoshiki Sawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Yamadaoka, 2-2, Suita-city, Osaka 565-0871 Japan
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Tsuzuki Y, Sanami S, Sugimoto K, Fujita S. Pseudo-nuclear staining of cells by deep learning improves the accuracy of automated cell counting in a label-free cellular population. J Biosci Bioeng 2020; 131:213-218. [PMID: 33077361 DOI: 10.1016/j.jbiosc.2020.09.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 08/21/2020] [Accepted: 09/22/2020] [Indexed: 11/18/2022]
Abstract
Deep learning has emerged as a breakthrough tool for the segmentation of images without supporting human experts. Here, we propose an automated approach that uses deep learning to generate pseudo-nuclear staining of cells from phase contrast images. Our proposed approach, which has the feature to generate pseudo-nuclear stained images by simple DNN, showed remarkable advantages over existing approaches in the cell-detection and the detection of the relative position of cells for various cell densities, as well as in counting the exact cell numbers. Pseudo-nuclear staining of cells by deep learning will improve the accuracy of automated cell counting in a label-free cellular population on phase contrast images.
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Affiliation(s)
- Yuji Tsuzuki
- Advance Business Center, ICT Business Development Division, Dai Nippon Printing Co., Ltd., 1-1-1 Ichigaya Kaga-cho, Shinjuku-ku, Tokyo 162-8001, Japan
| | - Sho Sanami
- Advance Business Center, ICT Business Development Division, Dai Nippon Printing Co., Ltd., 1-1-1 Ichigaya Kaga-cho, Shinjuku-ku, Tokyo 162-8001, Japan
| | - Kenji Sugimoto
- Live Cell Imaging Institute, University-Originated Venture, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Satoshi Fujita
- Advanced Photonics and Biosensing Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan; Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorioka, Ikeda, Osaka 563-0026, Japan.
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Kida Y, Fukunaga N, Sanami S, Watanabe H, Tsuzuki Y, Kitasaka H, Takeda S, Kondo F, Takeda S, Asada Y. IMPROVEMENT OF AN AUTOMATIC PRONUCLEAR DETECTION SYSTEM BY DEEP LEARNING TECHNOLOGY USING MULTI-SLICE IMAGES. Fertil Steril 2020. [DOI: 10.1016/j.fertnstert.2020.08.420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Watanabe H, Fukunaga N, Sanami S, Kitasaka H, Tsuzuki Y, Kida Y, Takeda S, Kondo F, Takeda S, Asada Y. COMPARISON OF PRONUCLEAR (PN) NUMBER OBSERVATIONS BASED ON EMBRYOLOGIST’S EXPERIENCE AND DETECTION BY ARTIFICAL INTELLIGENCE (AI) TRAINED WITH DEEP LEARNING TECHNOLOGY. Fertil Steril 2020. [DOI: 10.1016/j.fertnstert.2020.08.232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Kitasaka H, Fukunaga N, Sanami S, Watanabe H, Tsuzuki Y, Kida Y, Takeda S, Kondo F, Takeda S, Asada Y. INCREASING THE AMOUNT OF LEARNING DATA FOR DEEP LEARNING IS EFFECTIVE IN IMPROVING THE AUTOMATIC PRONUCLEUS NUMBER DETECTION SYSTEM FOR HUMAN EMBRYOS. Fertil Steril 2020. [DOI: 10.1016/j.fertnstert.2020.08.407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Fukunaga N, Sanami S, Kitasaka H, Tsuzuki Y, Watanabe H, Kida Y, Takeda S, Asada Y. Development of an automated two pronuclei detection system on time-lapse embryo images using deep learning techniques. Reprod Med Biol 2020; 19:286-294. [PMID: 32684828 PMCID: PMC7360969 DOI: 10.1002/rmb2.12331] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 05/02/2020] [Accepted: 05/15/2020] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To establish an automated pronuclei determination system by analysis using deep learning technology which is able to effectively learn with limited amount of supervised data. METHODS An algorithm was developed by explicitly incorporating human observation where the outline around pronuclei is being observed in determining the number of pronuclei. Supervised data were selected from the time-lapse images of 300 pronuclear stage embryos per class (total 900 embryos) clearly classified by embryologists as 0PN, 1PN, and 2PN. One-hundred embryos per class (a total of 300 embryos) were used for verification data. The verification data were evaluated for the performance of detection in the number of pronuclei by regarding the results consistent with the judgment of the embryologists as correct answers. RESULTS The sensitivity rates of 0PN, 1PN, and 2PN were 99%, 82%, and 99%, respectively, and the overlapping 2PN being difficult to determine by microscopic observation alone could also be appropriately assessed. CONCLUSIONS This study enabled the establishment of the automated pronuclei determination system with the precision almost equivalent to highly skilled embryologists.
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Affiliation(s)
- Noritaka Fukunaga
- Asada Ladies ClinicNagoyaJapan
- Asada Institute for Reproductive MedicineKasugaiJapan
| | - Sho Sanami
- Research & Development CenterDai Nippon Printing Co., LtdTokyoJapan
| | | | - Yuji Tsuzuki
- Research & Development CenterDai Nippon Printing Co., LtdTokyoJapan
| | | | | | - Seiji Takeda
- Research & Development CenterDai Nippon Printing Co., LtdTokyoJapan
| | - Yoshimasa Asada
- Asada Ladies ClinicNagoyaJapan
- Asada Institute for Reproductive MedicineKasugaiJapan
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11
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Mizuno M, Katano H, Shimozaki Y, Sanami S, Ozeki N, Koga H, Sekiya I. Time-lapse image analysis for whole colony growth curves and daily distribution of the cell number per colony during the expansion of mesenchymal stem cells. Sci Rep 2019; 9:16835. [PMID: 31728017 PMCID: PMC6856116 DOI: 10.1038/s41598-019-53383-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 10/31/2019] [Indexed: 12/24/2022] Open
Abstract
Mesenchymal stem cells from the synovium (synovial MSCs) are attractive for cartilage and meniscus regeneration therapy. We developed a software program that can distinguish individual colonies and automatically count the cell number per colony using time-lapse images. In this study, we investigated the usefulness of the software and analyzed colony formation in cultured synovial MSCs. Time-lapse image data were obtained for 14-day-expanded human synovial MSCs. The cell number per colony (for 145 colonies) was automatically counted from phase-contrast and nuclear-stained images. Colony growth curves from day 1 to day 14 (for 140 colonies) were classified using cluster analysis. Correlation analysis of the distribution of the cell number per colony at 14 days versus that number at 1–14 days revealed a correlation at 7 and 14 days. We obtained accurate cell number counts from phase-contrast images. Individual colony growth curves were classified into three main groups and subgroups. Our image analysis software has the potential to improve the evaluation of cell proliferation and to facilitate successful clinical applications using MSCs.
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Affiliation(s)
- Mitsuru Mizuno
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University, 1-5-45, Bunkyo-ku, Yushima, Tokyo, Japan
| | - Hisako Katano
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University, 1-5-45, Bunkyo-ku, Yushima, Tokyo, Japan
| | - Yuri Shimozaki
- Research & Development Center, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Sho Sanami
- Research & Development Center, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Nobutake Ozeki
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University, 1-5-45, Bunkyo-ku, Yushima, Tokyo, Japan
| | - Hideyuki Koga
- Department of Joint Surgery and Sports Medicine, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ichiro Sekiya
- Center for Stem Cell and Regenerative Medicine, Tokyo Medical and Dental University, 1-5-45, Bunkyo-ku, Yushima, Tokyo, Japan.
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Matsuura R, Miyagawa S, Fukushima S, Goto T, Harada A, Shimozaki Y, Yamaki K, Sanami S, Kikuta J, Ishii M, Sawa Y. Intravital imaging with two-photon microscopy reveals cellular dynamics in the ischeamia-reperfused rat heart. Sci Rep 2018; 8:15991. [PMID: 30375442 PMCID: PMC6207786 DOI: 10.1038/s41598-018-34295-w] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 10/09/2018] [Indexed: 12/27/2022] Open
Abstract
Recent advances in intravital microscopy have provided insight into dynamic biological events at the cellular level in both healthy and pathological tissue. However, real-time in vivo cellular imaging of the beating heart has not been fully established, mainly due to the difficulty of obtaining clear images through cycles of cardiac and respiratory motion. Here we report the successful recording of clear in vivo moving images of the beating rat heart by two-photon microscopy facilitated by cardiothoracic surgery and a novel cardiac stabiliser. Subcellular dynamics of the major cardiac components including the myocardium and its subcellular structures (i.e., nuclei and myofibrils) and mitochondrial distribution in cardiac myocytes were visualised for 4-5 h in green fluorescent protein-expressing transgenic Lewis rats at 15 frames/s. We also observed ischaemia/reperfusion (I/R) injury-induced suppression of the contraction/relaxation cycle and the consequent increase in cell permeability and leukocyte accumulation in cardiac tissue. I/R injury was induced in other transgenic mouse lines to further clarify the biological events in cardiac tissue. This imaging system can serve as an alternative modality for real time monitoring in animal models and cardiological drug screening, and can contribute to the development of more effective treatments for cardiac diseases.
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Affiliation(s)
- Ryohei Matsuura
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan.
| | - Shigeru Miyagawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Satsuki Fukushima
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Takasumi Goto
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Akima Harada
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yuri Shimozaki
- Research and Development Division for Advanced Technology, Research and Development Center, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Kazumasa Yamaki
- Research and Development Division for Advanced Technology, Research and Development Center, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Sho Sanami
- Research and Development Division for Advanced Technology, Research and Development Center, Dai Nippon Printing Co., Ltd., Tokyo, Japan
| | - Junichi Kikuta
- Department of Immunology and Cell Biology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Masaru Ishii
- Department of Immunology and Cell Biology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yoshiki Sawa
- Department of Cardiovascular Surgery, Osaka University Graduate School of Medicine, Osaka, Japan
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