Molecular Mechanisms of Vascular Disease

Fast, high-contrast imaging for investigating atherosclerosis and aneurysms

Raw widefield and THUNDER image of a mouse aorta Four_visualization_targets_in_a_mouse_aorta_THUNDERvsWidefield_teaser.jpg

This article discusses how the lamina, vascular cells, and nuclei of mouse aorta are more clearly resolved with a THUNDER Imager Tissue using Computational Clearing (CC) compared to conventional widefield microscopy. The causes of vascular diseases, such as atherosclerosis and thoracic aortic or cerebral aneurysms, are still not well understood. In particular, a better understanding of the molecular mechanisms effecting vascular diseases and how genetic variations can lead to heart attack is needed. This goal can be in part achieved with further research and investigation using such things as mouse models. For this study, thanks to the better contrast provided by the THUNDER Imager and CC, all 4 visualization targets of the mouse aorta specimen could be clearly visualized.

Introduction

One goal of research in the field of vascular biology is a better understanding of the genetic causes behind vascular diseases like atherosclerosis and aneurysms. Methods of molecular biology, such as mouse models, are exploited to investigate inherited genetic variations which promote smooth muscle cell dysfunction and can lead to heart attack or aneurysm rupture [1-3]. The ultimate goal would be early-phase clinical research. Discoveries that lead to a better comprehension of the molecular mechanisms that effect vascular disease may one day be translated into therapies for them [1-3]​​​​​​​. The results presented here show that the lamina, vascular cells, and nuclei of mouse aorta are more clearly resolved with a THUNDER Imager Tissue using Computational Clearing (CC) compared to conventional widefield microscopy.

Challenges

For this vascular disease research, it is practical to have an imaging solution that can quickly screen aorta specimens and acquire high-quality images which clearly resolve the targeted cells and structures. Thicker specimens require an imaging solution capable of good contrast at points deep inside them. Conventional widefield microscopy is fast and provides detection sensitivity, but the image contrast with thick specimens is significantly reduced by a blur or haze due to signals from out-of-focus planes [4,5]​​​​​​​.

Methods

Mouse aorta specimens expressing GFP, mCherry, and mOrange and stained with DAPI were imaged with a THUNDER Imager Tissue using Computational Clearing (CC). Vascular cells are green (GFP) and reddish orange (mOrange), elastic lamina are red (mCherry), and nuclei are blue (DAPI). With a THUNDER Imager and the LAS X software, researchers can acquire sharp images of complex specimens with the ease and speed of widefield microscopy  [4,5].

Results

The THUNDER image of the mouse aorta is shown below (refer to figure 1). From the raw widefield image, typically it can be hard to visualize the areas of interest due to autofluorescence and signal scattering by cholesterol and dead-cell material.

Conclusions

The computationally cleared images show an improvement in contrast of the four visualization targets in the mouse aorta specimen compared to conventional widefield imaging. From the THUNDER image, researchers gain clearer insights into the aorta.

References

  1. V. Nanda, T. Wang, M. Pjanic, B. Liu, T. Nguyen, L. Perisic Matic, U. Hedin, S. Koplev, L. Ma, O. Franzén, A. Ruusalepp, E.E. Schadt, J.L.M. Björkegren, S.B. Montgomery, M.P. Snyder, T. Quertermous, N.J. Leeper, C.L. Miller, Functional regulatory mechanism of smooth muscle cell-restricted LMOD1 coronary artery disease locus, PLOS Genet. (2018) vol. 14, no. 11, e1007755, DOI: 10.1371/journal.pgen.1007755.
  2. Y. Wang, H. Gao, F. Wang, Z. Ye, M. Mokry, A.W. Turner, J. Ye, S. Koplev, L. Luo, T. Alsaigh, S.S. Adkar, M. Elishaev, X. Gao, L. Maegdefessel, J.L.M. Björkegren, G. Pasterkamp, C.L. Miller, E.G. Ross, N.J. Leeper, Dynamic changes in chromatin accessibility are associated with the atherogenic transitioning of vascular smooth muscle cells, Cardiovascular Research (2021) cvab347, DOI: 10.1093/cvr/cvab347.
  3. Y. Kojima, J. Ye, V. Nanda, Y. Wang, A.M. Flores, K.-U. Jarr, P. Tsantilas, L. Guo, A.V. Finn, R. Virmani, N.J. Leeper, Knockout of the Murine Ortholog to the Human 9p21 Coronary Artery Disease Locus Leads to Smooth Muscle Cell Proliferation, Vascular Calcification, and Advanced Atherosclerosis, Circulation (2020) vol. 141, pp. 1274–1276, DOI: 10.1161/CIRCULATIONAHA.119.043413.
  4. J. Schumacher, L. Bertrand, THUNDER Technology Note: THUNDER Imagers: How Do They Really Work? Science Lab (2019) Leica Microsystems. 
  5. L. Felts, V. Kohli, J.M. Marr, J. Schumacher, O. Schlicker, An Introduction to Computational Clearing: A New Method to Remove Out-of-Focus Blur, Science Lab (2020) Leica Microsystems. 

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