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Heinen-Weiler J, Hasenberg M, Heisler M, Settelmeier S, Beerlage AL, Doepper H, Walkenfort B, Odersky A, Luedike P, Winterhager E, Rassaf T, Hendgen-Cotta UB. Superiority of focused ion beam-scanning electron microscope tomography of cardiomyocytes over standard 2D analyses highlighted by unmasking mitochondrial heterogeneity. J Cachexia Sarcopenia Muscle 2021; 12:933-954. [PMID: 34120411 PMCID: PMC8350221 DOI: 10.1002/jcsm.12742] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 04/16/2021] [Accepted: 05/21/2021] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Cardioprotection by preventing or repairing mitochondrial damage is an unmet therapeutic need. To understand the role of cardiomyocyte mitochondria in physiopathology, the reliable characterization of the mitochondrial morphology and compartment is pivotal. Previous studies mostly relied on two-dimensional (2D) routine transmission electron microscopy (TEM), thereby neglecting the real three-dimensional (3D) mitochondrial organization. This study aimed to determine whether classical 2D TEM analysis of the cardiomyocyte ultrastructure is sufficient to comprehensively describe the mitochondrial compartment and to reflect mitochondrial number, size, dispersion, distribution, and morphology. METHODS Spatial distribution of the complex mitochondrial network and morphology, number, and size heterogeneity of cardiac mitochondria in isolated adult mouse cardiomyocytes and adult wild-type left ventricular tissues (C57BL/6) were assessed using a comparative 3D imaging system based on focused ion beam-scanning electron microscopy (FIB-SEM) nanotomography. For comparison of 2D vs. 3D data sets, analytical strategies and mathematical comparative approaches were performed. To confirm the value of 3D data for mitochondrial changes, we compared the obtained values for number, coverage area, size heterogeneity, and complexity of wild-type cardiomyocyte mitochondria with data sets from mice lacking the cytosolic and mitochondrial protein BNIP3 (BCL-2/adenovirus E1B 19-kDa interacting protein 3; Bnip3-/- ) using FIB-SEM. Mitochondrial respiration was assessed on isolated mitochondria using the Seahorse XF analyser. A cardiac biopsy was obtained from a male patient (48 years) suffering from myocarditis. RESULTS The FIB-SEM nanotomographic analysis revealed that no linear relationship exists for mitochondrial number (r = 0.02; P = 0.9511), dispersion (r = -0.03; P = 0.9188), and shape (roundness: r = 0.15, P = 0.6397; elongation: r = -0.09, P = 0.7804) between 3D and 2D results. Cumulative frequency distribution analysis showed a diverse abundance of mitochondria with different sizes in 3D and 2D. Qualitatively, 2D data could not reflect mitochondrial distribution and dynamics existing in 3D tissue. 3D analyses enabled the discovery that BNIP3 deletion resulted in more smaller, less complex cardiomyocyte mitochondria (number: P < 0.01; heterogeneity: C.V. wild-type 89% vs. Bnip3-/- 68%; complexity: P < 0.001) forming large myofibril-distorting clusters, as seen in human myocarditis with disturbed mitochondrial dynamics. Bnip3-/- mice also show a higher respiration rate (P < 0.01). CONCLUSIONS Here, we demonstrate the need of 3D analyses for the characterization of mitochondrial features in cardiac tissue samples. Hence, we observed that BNIP3 deletion physiologically acts as a molecular brake on mitochondrial number, suggesting a role in mitochondrial fusion/fission processes and thereby regulating the homeostasis of cardiac bioenergetics.
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Affiliation(s)
- Jacqueline Heinen-Weiler
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany.,Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Mike Hasenberg
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Martin Heisler
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Stephan Settelmeier
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Anna-Lena Beerlage
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Hannah Doepper
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Bernd Walkenfort
- Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Andrea Odersky
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Peter Luedike
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Elke Winterhager
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany.,Imaging Center Essen (IMCES), Electron Microscopy Unit (EMU), Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Tienush Rassaf
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Ulrike B Hendgen-Cotta
- Department of Cardiology and Vascular Medicine, West German Heart and Vascular Center, Medical Faculty, University of Duisburg-Essen, Essen, Germany
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Mueller-Buehl AM, Doepper H, Grauthoff S, Kiebler T, Peters L, Hurst J, Kuehn S, Bartz-Schmidt KU, Dick HB, Joachim SC, Schnichels S. Oxidative stress-induced retinal damage is prevented by mild hypothermia in an ex vivo model of cultivated porcine retinas. Clin Exp Ophthalmol 2020; 48:666-681. [PMID: 32077190 DOI: 10.1111/ceo.13731] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 01/15/2020] [Accepted: 02/17/2020] [Indexed: 12/25/2022]
Abstract
BACKGROUND Hydrogen peroxide (H2 O2 ) can be used in vitro to simulate oxidative stress. In retinal organ cultures, H2 O2 induces strong neurodegeneration of the retina. It is known that oxidative stress plays a role in the development of several retinal diseases including glaucoma and ischemia. Thus, we investigated whether processes underlying oxidative stress can be prevented by hypothermia using an ex vivo organ culture model of porcine retinas. METHODS Porcine retinal explants were cultivated for 5 and 8 days. Oxidative stress was induced via 300 μM H2 O2 on day 1 for 3 hours. Hypothermia treatment at 30°C was applied simultaneously with H2 O2 , for 3 hours. Retinal ganglion cells (RGCs), apoptosis, bipolar and cholinergic amacrine cells, microglia and macroglia were evaluated immunohistologically. Apoptosis rate was additionally analysed via western blot. RESULTS Reduced apoptosis rates through hypothermia led to a preservation of RGCs (P < .001). Amacrine cells were rescued after hypothermia treatment (P = .17), whereas bipolar cells were only protected partly. Additionally, at 8 days, microglial response due to oxidative stress was completely counteracted via hypothermia (P < .001). CONCLUSIONS H2 O2 induced strong degenerative processes in porcine retinas. The role of oxidative stress in the progression of retinal diseases makes this ex vivo organ culture model suitable to investigate new therapeutic approaches. In the present study, the damaging effect of H2 O2 to several retinal cell types was counteracted or strongly alleviated through hypothermia treatment. Especially RGCs, which are affected in glaucoma disease, were protected due to a reduced apoptosis rate through hypothermia.
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Affiliation(s)
- Ana M Mueller-Buehl
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Hannah Doepper
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sven Grauthoff
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Tobias Kiebler
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Laura Peters
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - José Hurst
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - Sandra Kuehn
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Karl U Bartz-Schmidt
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
| | - H Burkard Dick
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Stephanie C Joachim
- Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Bochum, Germany
| | - Sven Schnichels
- Centre for Ophthalmology Tübingen, University Eye Hospital Tübingen, Tübingen, Germany
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