PI Megens

Biophysics of Microscopy - Cardiovascular Imaging Technologies

Biophysik der Mikroskopie - Kardiovaskuläre Bildgebung

 

In order to further elucidate the processes involved in initiation and progression of atherosclerosis, insight in cardiovascular structure and function is essential. Histology has provided a detailed insight in various aspects of human and experimental atherosclerosis. However, the utilized preparation methods in histology limit studying structure and of atherosclerotic plaques in the whole mount plaque or under physiologically relevant circumstances. In order to study the contribution of various inflammatory cell subsets to the disease, it is a prerequisite to study the process of atherosclerosis in vivo.

The IPEK working group on biophysics of microscopy focusses on the application of advanced optical fluorescence techniques such as two-photon laser scanning microscopy (TPLSM), stimulated emission depletion (STED), and dual channel intravital microscopy, for (molecular) imaging of atherosclerotic structures and processes directly at sites of occurrence: i.e. the large arteries [1-3]. In the past years, application of TPLSM in cardiovascular research enabled imaging of structures deep in the large arterial wall in up to four dimensions due to its improved depth penetration and optical sectioning properties. For in vivo imaging of atherosclerosis, the impact of motion on imaging could be circumvented by usage of TPLSM imaging triggered on the heart and respiration cycle of the animal under subject [4]. The latter TPLSM methodologies have been successfully applied in various studies conducted within IPEK and its collaborators [5-9].

Picture_AG Megens_scaled

Figure: examples TPLSM in mouse cardiovascular tissue: in vivo detection of NETs (red) (a) and neutrophil diapedesis (green) (b) over time (0-30 minutes) in atherosclerotic prone carotid artery [5, 6]; c) ex vivo atherosclerotic plaque foam cells (green/ red); d) 3D projection of Luminal CRAMP deposition detected by anti-CRAMP coated latex beads (green) [8]; e) 3D projection of CD11c positive dendritic cells (green) in aortic root ex vivo [7]; f) 3D projection of a regulatory T-cell (red) colocalization with CCL17 positive dendritic cells (green) in atherosclerotic carotid artery [7].

 

In December 2011, a state-of-the-art TPLSM system was installed at IPEK. This LEICA SP5 MP (funded by DFG/LMU) offers fast image acquisition rates (30Hz at full resolution) and improved sensitivity. As a result, in vivo imaging of cardiovasculature can be taken to a higher level with regard to both spatial and time resolution in up to four dimensions. The PI Megens group will further develop in vivo TPLSM applications for imaging in (diseased) cardiovascular targets and apply them in projects studying inflammatory cell recruitment, proteases(activity), vessel wall structures and their function, cell-cell interactions, and cellular processes such as formation of Neutrophil extracellular traps (NETs). Besides in vivo application, TPLSM will also be used for imaging of isolated whole mount specimen ex vivo. Finally, the PI Megens laboratory functions as a TPLSM imaging core facility for internal and external collaborators.

 

Literature

1. Megens, R.T.A., et al., Imaging collagen in intact viable healthy and atherosclerotic arteries using fluorescently labeled CNA35 and two-photon laser scanning microscopy. Molecular imaging, 2007. 6(4): p. 247-60.

2. Megens, R.T.A., et al., Two-photon microscopy on vital carotid arteries: imaging the relationship between collagen and inflammatory cells in atherosclerotic plaques. J Biomed Opt, 2008. 13(4): p. 044022.

3. Megens, R.T.A., et al., Two-photon microscopy of vital murine elastic and muscular arteries. Combined structural and functional imaging with subcellular resolution. J Vasc Res, 2007. 44(2): p. 87-98.

4. Megens, R.T.A., et al., In vivo high-resolution structural imaging of large arteries in small rodents using two-photon laser scanning microscopy. J Biomed Opt, 2010. 15(1): p. 011108.

5. Drechsler, M., et al., Hyperlipidemia-triggered neutrophilia promotes early atherosclerosis. Circulation, 2010. 122(18): p. 1837-45.

6. Megens, R.T.A., et al., Presence of luminal neutrophil extracellular traps in atherosclerosis. Thrombosis and Haemostasis, 2012.8;107(3). [Epub ahead of print].

7. Weber, C., et al., CCL17-expressing dendritic cells drive atherosclerosis by restraining regulatory T cell homeostasis in mice. J Clin Invest, 2011. 121(7): p. 2898-910.

8. Soehnlein, O., et al., Neutrophil-derived cathelicidin protects from neointimal hyperplasia. Science translational medicine, 2011. 3(103): p. 103ra98.

9. Zhou, Z., et al., Lipoprotein-derived lysophosphatidic acid promotes atherosclerosis by releasing CXCL1 from the endothelium. Cell metabolism, 2011. 13(5): p. 592-600.

 

Principal Investigator:

Dr. rer.nat. Remco Megens

 

Group members:

Mariaelvy Bianchini

 
 
IPEKlogo

Direktor: Prof. Dr. med. Christian Weber

Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten (IPEK)

 

Pettenkoferstraße 8a & 9

80336 München

 

Tel.: 089-4400-54351

Fax: 089-4400-54352

Mail: Kreislaufinstitut@med.uni-muenchen.de

 

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